BaseDataList.cs source code in C# .NET

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Code:

/ 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / xsp / System / Web / UI / WebControls / BaseDataList.cs / 1305376 / BaseDataList.cs

                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.ComponentModel;
    using System.ComponentModel.Design;
    using System.Web;
    using System.Web.UI; 
    using System.Web.Util;
 
    ///  
    /// Serves as the abstract base class for the  and 
    /// controls and implements the selection semantics which are common to both 
    /// controls.
    /// 
    [
    DefaultEvent("SelectedIndexChanged"), 
    DefaultProperty("DataSource"),
    Designer("System.Web.UI.Design.WebControls.BaseDataListDesigner, " + AssemblyRef.SystemDesign) 
    ] 
    public abstract class BaseDataList : WebControl {
 
        private static readonly object EventSelectedIndexChanged = new object();

        internal const string ItemCountViewStateKey = "_!ItemCount";
 
        private object dataSource;
        private DataKeyCollection dataKeysCollection; 
        private bool _requiresDataBinding; 
        private bool _inited;
        private bool _throwOnDataPropertyChange; 

        private DataSourceView _currentView;
        private bool _currentViewIsFromDataSourceID;
        private bool _currentViewValid; 
        private DataSourceSelectArguments _arguments;
        private bool _pagePreLoadFired; 
 

        [ 
        DefaultValue(""),
        Localizable(true),
        WebCategory("Accessibility"),
        WebSysDescription(SR.DataControls_Caption) 
        ]
        public virtual string Caption { 
            get { 
                string s = (string)ViewState["Caption"];
                return (s != null) ? s : String.Empty; 
            }
            set {
                ViewState["Caption"] = value;
            } 
        }
 
 
        [
        DefaultValue(TableCaptionAlign.NotSet), 
        WebCategory("Accessibility"),
        WebSysDescription(SR.WebControl_CaptionAlign)
        ]
        public virtual TableCaptionAlign CaptionAlign { 
            get {
                object o = ViewState["CaptionAlign"]; 
                return (o != null) ? (TableCaptionAlign)o : TableCaptionAlign.NotSet; 
            }
            set { 
                if ((value < TableCaptionAlign.NotSet) ||
                    (value > TableCaptionAlign.Right)) {
                    throw new ArgumentOutOfRangeException("value");
                } 
                ViewState["CaptionAlign"] = value;
            } 
        } 

 
        /// 
        ///    Indicates the amount of space between cells.
        /// 
        [ 
        WebCategory("Layout"),
        DefaultValue(-1), 
        WebSysDescription(SR.BaseDataList_CellPadding) 
        ]
        public virtual int CellPadding { 
            get {
                if (ControlStyleCreated == false) {
                    return -1;
                } 
                return ((TableStyle)ControlStyle).CellPadding;
            } 
            set { 
                ((TableStyle)ControlStyle).CellPadding = value;
            } 
        }


        ///  
        ///    Gets or sets the amount of space between the contents of
        ///       a cell and the cell's border. 
        ///  
        [
        WebCategory("Layout"), 
        DefaultValue(0),
        WebSysDescription(SR.BaseDataList_CellSpacing)
        ]
        public virtual int CellSpacing { 
            get {
                if (ControlStyleCreated == false) { 
                    return 0; 
                }
                return ((TableStyle)ControlStyle).CellSpacing; 
            }
            set {
                ((TableStyle)ControlStyle).CellSpacing = value;
            } 
        }
 
 
        public override ControlCollection Controls {
            get { 
                EnsureChildControls();
                return base.Controls;
            }
        } 

 
        ///  
        /// 
        [ 
        Browsable(false),
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
        WebSysDescription(SR.BaseDataList_DataKeys)
        ] 
        public DataKeyCollection DataKeys {
            get { 
                if (dataKeysCollection == null) { 
                    dataKeysCollection = new DataKeyCollection(this.DataKeysArray);
                } 
                return dataKeysCollection;
            }
        }
 

        ///  
        ///  
        protected ArrayList DataKeysArray {
            get { 
                object o = ViewState["DataKeys"];
                if (o == null) {
                    o = new ArrayList();
                    ViewState["DataKeys"] = o; 
                }
                return(ArrayList)o; 
            } 
        }
 


        /// 
        /// Indicatesthe primary key field in the data source referenced by . 
        /// 
        [ 
        DefaultValue(""), 
        Themeable(false),
        WebCategory("Data"), 
        WebSysDescription(SR.BaseDataList_DataKeyField)
        ]
        public virtual string DataKeyField {
            get { 
                object o = ViewState["DataKeyField"];
                if (o != null) 
                    return(string)o; 
                return String.Empty;
            } 
            set {
                ViewState["DataKeyField"] = value;
            }
        } 

 
        ///  
        /// 
        [ 
        DefaultValue(""),
        Themeable(false),
        WebCategory("Data"),
        WebSysDescription(SR.BaseDataList_DataMember) 
        ]
        public string DataMember { 
            get { 
                object o = ViewState["DataMember"];
                if (o != null) 
                    return (string)o;
                return String.Empty;
            }
            set { 
                ViewState["DataMember"] = value;
                OnDataPropertyChanged(); 
            } 
        }
 

        /// 
        ///    Gets
        ///       or sets the source to a list of values used to populate 
        ///       the items within the control.
        ///  
        [ 
        Bindable(true),
        DefaultValue(null), 
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
        Themeable(false),
        WebCategory("Data"),
        WebSysDescription(SR.BaseDataBoundControl_DataSource), 
        ]
        public virtual object DataSource { 
            get { 
                return dataSource;
            } 
            set {
                if ((value == null) || (value is IListSource) || (value is IEnumerable)) {
                    dataSource = value;
                    OnDataPropertyChanged(); 
                }
                else { 
                    throw new ArgumentException(SR.GetString(SR.Invalid_DataSource_Type, ID)); 
                }
            } 
        }


        ///  
        /// The ID of the DataControl that this control should use to retrieve
        /// its data source. When the control is bound to a DataControl, it 
        /// can retrieve a data source instance on-demand, and thereby attempt 
        /// to work in auto-DataBind mode.
        ///  
        [
        DefaultValue(""),
        IDReferenceProperty(typeof(DataSourceControl)),
        Themeable(false), 
        WebCategory("Data"),
        WebSysDescription(SR.BaseDataBoundControl_DataSourceID) 
        ] 
        public virtual string DataSourceID {
            get { 
                object o = ViewState["DataSourceID"];
                if (o != null) {
                    return (string)o;
                } 
                return String.Empty;
            } 
            set { 
                ViewState["DataSourceID"] = value;
                OnDataPropertyChanged(); 
            }
        }

 
        /// 
        ///    Gets or sets a value that specifies the grid line style. 
        ///  
        [
        WebCategory("Appearance"), 
        DefaultValue(GridLines.Both),
        WebSysDescription(SR.DataControls_GridLines)
        ]
        public virtual GridLines GridLines { 
            get {
                if (ControlStyleCreated == false) { 
                    return GridLines.Both; 
                }
                return ((TableStyle)ControlStyle).GridLines; 
            }
            set {
                ((TableStyle)ControlStyle).GridLines = value;
            } 
        }
 
 
        /// 
        ///    Gets or sets a value that specifies the alignment of a rows with respect 
        ///       surrounding text.
        /// 
        [
        Category("Layout"), 
        DefaultValue(HorizontalAlign.NotSet),
        WebSysDescription(SR.WebControl_HorizontalAlign) 
        ] 
        public virtual HorizontalAlign HorizontalAlign {
            get { 
                if (ControlStyleCreated == false) {
                    return HorizontalAlign.NotSet;
                }
                return ((TableStyle)ControlStyle).HorizontalAlign; 
            }
            set { 
                ((TableStyle)ControlStyle).HorizontalAlign = value; 
            }
        } 


        protected bool Initialized {
            get { 
                return _inited;
            } 
        } 

 
        protected bool IsBoundUsingDataSourceID {
            get {
                return (DataSourceID.Length > 0);
            } 
        }
 
        public override bool SupportsDisabledAttribute { 
            get {
                return RenderingCompatibility < VersionUtil.Framework40; 
            }
        }

        protected bool RequiresDataBinding { 
            get {
                return _requiresDataBinding; 
            } 
            set {
                _requiresDataBinding = value; 
            }
        }

        protected DataSourceSelectArguments SelectArguments { 
            get {
                if (_arguments == null) { 
                    _arguments = CreateDataSourceSelectArguments(); 
                }
                return _arguments; 
            }
        }

 
        [
        DefaultValue(false), 
        WebCategory("Accessibility"), 
        WebSysDescription(SR.Table_UseAccessibleHeader)
        ] 
        public virtual bool UseAccessibleHeader {
            get {
                object b = ViewState["UseAccessibleHeader"];
                return (b != null) ? (bool)b : false; 
            }
            set { 
                ViewState["UseAccessibleHeader"] = value; 
            }
        } 


        /// 
        ///    Occurs when an item on the list is selected. 
        /// 
        [ 
        WebCategory("Action"), 
        WebSysDescription(SR.BaseDataList_OnSelectedIndexChanged)
        ] 
        public event EventHandler SelectedIndexChanged {
            add {
                Events.AddHandler(EventSelectedIndexChanged, value);
            } 
            remove {
                Events.RemoveHandler(EventSelectedIndexChanged, value); 
            } 
        }
 

        /// 
        ///     Not coded yet.
        ///  
        protected override void AddParsedSubObject(object obj) {
            return; 
        } 

        ///  
        /// Connects this data bound control to the appropriate DataSourceView
        /// and hooks up the appropriate event listener for the
        /// DataSourceViewChanged event. The return value is the new view (if
        /// any) that was connected to. An exception is thrown if there is 
        /// a problem finding the requested view or data source.
        ///  
        private DataSourceView ConnectToDataSourceView() { 
            if (_currentViewValid && !DesignMode) {
                // If the current view is correct, there is no need to reconnect 
                return _currentView;
            }

            // Disconnect from old view, if necessary 
            if ((_currentView != null) && (_currentViewIsFromDataSourceID)) {
                // We only care about this event if we are bound through the DataSourceID property 
                _currentView.DataSourceViewChanged -= new EventHandler(OnDataSourceViewChanged); 
            }
 
            // Connect to new view
            IDataSource ds = null;
            string dataSourceID = DataSourceID;
 
            if (dataSourceID.Length != 0) {
                // Try to find a DataSource control with the ID specified in DataSourceID 
                Control control = DataBoundControlHelper.FindControl(this, dataSourceID); 
                if (control == null) {
                    throw new HttpException(SR.GetString(SR.DataControl_DataSourceDoesntExist, ID, dataSourceID)); 
                }
                ds = control as IDataSource;
                if (ds == null) {
                    throw new HttpException(SR.GetString(SR.DataControl_DataSourceIDMustBeDataControl, ID, dataSourceID)); 
                }
            } 
 
            if (ds == null) {
                // DataSource control was not found, construct a temporary data source to wrap the data 
                ds = new ReadOnlyDataSource(DataSource, DataMember);
            }
            else {
                // Ensure that both DataSourceID as well as DataSource are not set at the same time 
                if (DataSource != null) {
                    throw new InvalidOperationException(SR.GetString(SR.DataControl_MultipleDataSources, ID)); 
                } 
            }
 
            // IDataSource was found, extract the appropriate view and return it
            DataSourceView newView = ds.GetView(DataMember);
            if (newView == null) {
                throw new InvalidOperationException(SR.GetString(SR.DataControl_ViewNotFound, ID)); 
            }
 
            _currentViewIsFromDataSourceID = IsBoundUsingDataSourceID; 
            _currentView = newView;
            if ((_currentView != null) && (_currentViewIsFromDataSourceID)) { 
                // We only care about this event if we are bound through the DataSourceID property
                _currentView.DataSourceViewChanged += new EventHandler(OnDataSourceViewChanged);
            }
            _currentViewValid = true; 

            return _currentView; 
        } 

 
        /// 
        /// 
        ///    Creates a child control using the view state.
        ///  
        protected internal override void CreateChildControls() {
            Controls.Clear(); 
 
            if (ViewState[ItemCountViewStateKey] == null) {
                if (RequiresDataBinding) { 
                    EnsureDataBound();
                }
            }
            else { 
                // create the control hierarchy using the view state (and
                // not the datasource) 
                CreateControlHierarchy(false); 
                ClearChildViewState();
            } 
        }


        protected abstract void CreateControlHierarchy(bool useDataSource); 

 
        public override void DataBind() { 
            // Don't databind to a data source control when the control is in the designer but not top-level
            if (IsBoundUsingDataSourceID && DesignMode && (Site == null)) { 
                return;
            }

            // do our own databinding 
            RequiresDataBinding = false;
            OnDataBinding(EventArgs.Empty); 
        } 

        protected virtual DataSourceSelectArguments CreateDataSourceSelectArguments() { 
            return DataSourceSelectArguments.Empty;
        }

 
        protected void EnsureDataBound() {
            try { 
                _throwOnDataPropertyChange = true; 
                if (RequiresDataBinding && DataSourceID.Length > 0) {
                    DataBind(); 
                }
            }
            finally {
                _throwOnDataPropertyChange = false; 
            }
        } 
 

        ///  
        /// Returns an IEnumerable that is the DataSource, which either came
        /// from the DataSource property or from the control bound via the
        /// DataSourceID property.
        ///  
        protected virtual IEnumerable GetData() {
            ConnectToDataSourceView(); 
 
            Debug.Assert(_currentViewValid);
 
            if (_currentView != null) {
                return _currentView.ExecuteSelect(SelectArguments);
            }
            return null; 
        }
 
 
        /// 
        ///    Determines if the specified data type can be bound to. 
        /// 
        public static bool IsBindableType(Type type) {
            return(type.IsPrimitive ||
                   (type == typeof(string)) || 
                   (type == typeof(DateTime)) ||
                   (type == typeof(Decimal))); 
        } 

 
        /// 
        /// 
        /// Raises the event of a 
        /// . 
        /// 
        protected override void OnDataBinding(EventArgs e) { 
            base.OnDataBinding(e); 

            // reset the control state 
            Controls.Clear();
            ClearChildViewState();

            // and create the control hierarchy using the datasource 
            dataKeysCollection = null;
            CreateControlHierarchy(true); 
            ChildControlsCreated = true; 

            TrackViewState(); 
        }


        ///  
        ///  This method is called when DataMember, DataSource, or DataSourceID is changed.
        ///  
        protected virtual void OnDataPropertyChanged() { 
            if (_throwOnDataPropertyChange) {
                throw new HttpException(SR.GetString(SR.DataBoundControl_InvalidDataPropertyChange, ID)); 
            }

            if (_inited) {
                RequiresDataBinding = true; 
            }
            _currentViewValid = false; 
        } 

 
        protected virtual void OnDataSourceViewChanged(object sender, EventArgs e) {
            RequiresDataBinding = true;
        }
 

        protected internal override void OnInit(EventArgs e) { 
            base.OnInit(e); 

            if (Page != null) { 
                Page.PreLoad += new EventHandler(this.OnPagePreLoad);

                if (!IsViewStateEnabled && Page.IsPostBack) {
                    RequiresDataBinding = true; 
                }
            } 
        } 

 
        protected internal override void OnLoad(EventArgs e) {
            _inited = true; // just in case we were added to the page after PreLoad
            ConnectToDataSourceView();
            if (Page != null &&  !_pagePreLoadFired && ViewState[ItemCountViewStateKey] == null) { 
                // If the control was added after PagePreLoad, we still need to databind it because it missed its
                // first change in PagePreLoad.  If this control was created by a call to a parent control's DataBind 
                // in Page_Load (with is relatively common), this control will already have been databound even 
                // though pagePreLoad never fired and the page isn't a postback.
                if (!Page.IsPostBack) { 
                    RequiresDataBinding = true;
                }

                // If the control was added to the page after page.PreLoad, we'll never get the event and we'll 
                // never databind the control.  So if we're catching up and Load happens but PreLoad never happened,
                // call DataBind.  This may make the control get databound twice if the user called DataBind on the control 
                // directly in Page.OnLoad, but better to bind twice than never to bind at all. 
                else if (IsViewStateEnabled) {
                    RequiresDataBinding = true; 
                }
            }

            base.OnLoad(e); 
        }
 
        private void OnPagePreLoad(object sender, EventArgs e) { 
            _inited = true;
 
            if (Page != null) {
                Page.PreLoad -= new EventHandler(this.OnPagePreLoad);

                // Setting RequiresDataBinding to true in OnLoad is too late because the OnLoad page event 
                // happens before the control.OnLoad method gets called.  So a page_load handler on the page
                // that calls DataBind won't prevent DataBind from getting called again in PreRender. 
                if (!Page.IsPostBack) { 
                    RequiresDataBinding = true;
                } 

                // If this is a postback and viewstate is enabled, but we have never bound the control
                // before, it is probably because its visibility was changed in the postback.  In this
                // case, we need to bind the control or it will never appear.  This is a common scenario 
                // for Wizard and MultiView.
                if (Page.IsPostBack && IsViewStateEnabled && ViewState[ItemCountViewStateKey] == null) { 
                    RequiresDataBinding = true; 
                }
            } 
            _pagePreLoadFired = true;
        }

 
        protected internal override void OnPreRender(EventArgs e) {
            EnsureDataBound(); 
            base.OnPreRender(e); 
        }
 

        /// 
        /// Raises the event of a .
        ///  
        protected virtual void OnSelectedIndexChanged(EventArgs e) {
            EventHandler handler = (EventHandler)Events[EventSelectedIndexChanged]; 
            if (handler != null) handler(this, e); 
        }
 

        protected internal abstract void PrepareControlHierarchy();

 
        /// 
        ///  
        ///    Displays the control on the client. 
        /// 
        protected internal override void Render(HtmlTextWriter writer) { 
            PrepareControlHierarchy();
            RenderContents(writer);
        }
    } 
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.ComponentModel;
    using System.ComponentModel.Design;
    using System.Web;
    using System.Web.UI; 
    using System.Web.Util;
 
    ///  
    /// Serves as the abstract base class for the  and 
    /// controls and implements the selection semantics which are common to both 
    /// controls.
    /// 
    [
    DefaultEvent("SelectedIndexChanged"), 
    DefaultProperty("DataSource"),
    Designer("System.Web.UI.Design.WebControls.BaseDataListDesigner, " + AssemblyRef.SystemDesign) 
    ] 
    public abstract class BaseDataList : WebControl {
 
        private static readonly object EventSelectedIndexChanged = new object();

        internal const string ItemCountViewStateKey = "_!ItemCount";
 
        private object dataSource;
        private DataKeyCollection dataKeysCollection; 
        private bool _requiresDataBinding; 
        private bool _inited;
        private bool _throwOnDataPropertyChange; 

        private DataSourceView _currentView;
        private bool _currentViewIsFromDataSourceID;
        private bool _currentViewValid; 
        private DataSourceSelectArguments _arguments;
        private bool _pagePreLoadFired; 
 

        [ 
        DefaultValue(""),
        Localizable(true),
        WebCategory("Accessibility"),
        WebSysDescription(SR.DataControls_Caption) 
        ]
        public virtual string Caption { 
            get { 
                string s = (string)ViewState["Caption"];
                return (s != null) ? s : String.Empty; 
            }
            set {
                ViewState["Caption"] = value;
            } 
        }
 
 
        [
        DefaultValue(TableCaptionAlign.NotSet), 
        WebCategory("Accessibility"),
        WebSysDescription(SR.WebControl_CaptionAlign)
        ]
        public virtual TableCaptionAlign CaptionAlign { 
            get {
                object o = ViewState["CaptionAlign"]; 
                return (o != null) ? (TableCaptionAlign)o : TableCaptionAlign.NotSet; 
            }
            set { 
                if ((value < TableCaptionAlign.NotSet) ||
                    (value > TableCaptionAlign.Right)) {
                    throw new ArgumentOutOfRangeException("value");
                } 
                ViewState["CaptionAlign"] = value;
            } 
        } 

 
        /// 
        ///    Indicates the amount of space between cells.
        /// 
        [ 
        WebCategory("Layout"),
        DefaultValue(-1), 
        WebSysDescription(SR.BaseDataList_CellPadding) 
        ]
        public virtual int CellPadding { 
            get {
                if (ControlStyleCreated == false) {
                    return -1;
                } 
                return ((TableStyle)ControlStyle).CellPadding;
            } 
            set { 
                ((TableStyle)ControlStyle).CellPadding = value;
            } 
        }


        ///  
        ///    Gets or sets the amount of space between the contents of
        ///       a cell and the cell's border. 
        ///  
        [
        WebCategory("Layout"), 
        DefaultValue(0),
        WebSysDescription(SR.BaseDataList_CellSpacing)
        ]
        public virtual int CellSpacing { 
            get {
                if (ControlStyleCreated == false) { 
                    return 0; 
                }
                return ((TableStyle)ControlStyle).CellSpacing; 
            }
            set {
                ((TableStyle)ControlStyle).CellSpacing = value;
            } 
        }
 
 
        public override ControlCollection Controls {
            get { 
                EnsureChildControls();
                return base.Controls;
            }
        } 

 
        ///  
        /// 
        [ 
        Browsable(false),
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
        WebSysDescription(SR.BaseDataList_DataKeys)
        ] 
        public DataKeyCollection DataKeys {
            get { 
                if (dataKeysCollection == null) { 
                    dataKeysCollection = new DataKeyCollection(this.DataKeysArray);
                } 
                return dataKeysCollection;
            }
        }
 

        ///  
        ///  
        protected ArrayList DataKeysArray {
            get { 
                object o = ViewState["DataKeys"];
                if (o == null) {
                    o = new ArrayList();
                    ViewState["DataKeys"] = o; 
                }
                return(ArrayList)o; 
            } 
        }
 


        /// 
        /// Indicatesthe primary key field in the data source referenced by . 
        /// 
        [ 
        DefaultValue(""), 
        Themeable(false),
        WebCategory("Data"), 
        WebSysDescription(SR.BaseDataList_DataKeyField)
        ]
        public virtual string DataKeyField {
            get { 
                object o = ViewState["DataKeyField"];
                if (o != null) 
                    return(string)o; 
                return String.Empty;
            } 
            set {
                ViewState["DataKeyField"] = value;
            }
        } 

 
        ///  
        /// 
        [ 
        DefaultValue(""),
        Themeable(false),
        WebCategory("Data"),
        WebSysDescription(SR.BaseDataList_DataMember) 
        ]
        public string DataMember { 
            get { 
                object o = ViewState["DataMember"];
                if (o != null) 
                    return (string)o;
                return String.Empty;
            }
            set { 
                ViewState["DataMember"] = value;
                OnDataPropertyChanged(); 
            } 
        }
 

        /// 
        ///    Gets
        ///       or sets the source to a list of values used to populate 
        ///       the items within the control.
        ///  
        [ 
        Bindable(true),
        DefaultValue(null), 
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
        Themeable(false),
        WebCategory("Data"),
        WebSysDescription(SR.BaseDataBoundControl_DataSource), 
        ]
        public virtual object DataSource { 
            get { 
                return dataSource;
            } 
            set {
                if ((value == null) || (value is IListSource) || (value is IEnumerable)) {
                    dataSource = value;
                    OnDataPropertyChanged(); 
                }
                else { 
                    throw new ArgumentException(SR.GetString(SR.Invalid_DataSource_Type, ID)); 
                }
            } 
        }


        ///  
        /// The ID of the DataControl that this control should use to retrieve
        /// its data source. When the control is bound to a DataControl, it 
        /// can retrieve a data source instance on-demand, and thereby attempt 
        /// to work in auto-DataBind mode.
        ///  
        [
        DefaultValue(""),
        IDReferenceProperty(typeof(DataSourceControl)),
        Themeable(false), 
        WebCategory("Data"),
        WebSysDescription(SR.BaseDataBoundControl_DataSourceID) 
        ] 
        public virtual string DataSourceID {
            get { 
                object o = ViewState["DataSourceID"];
                if (o != null) {
                    return (string)o;
                } 
                return String.Empty;
            } 
            set { 
                ViewState["DataSourceID"] = value;
                OnDataPropertyChanged(); 
            }
        }

 
        /// 
        ///    Gets or sets a value that specifies the grid line style. 
        ///  
        [
        WebCategory("Appearance"), 
        DefaultValue(GridLines.Both),
        WebSysDescription(SR.DataControls_GridLines)
        ]
        public virtual GridLines GridLines { 
            get {
                if (ControlStyleCreated == false) { 
                    return GridLines.Both; 
                }
                return ((TableStyle)ControlStyle).GridLines; 
            }
            set {
                ((TableStyle)ControlStyle).GridLines = value;
            } 
        }
 
 
        /// 
        ///    Gets or sets a value that specifies the alignment of a rows with respect 
        ///       surrounding text.
        /// 
        [
        Category("Layout"), 
        DefaultValue(HorizontalAlign.NotSet),
        WebSysDescription(SR.WebControl_HorizontalAlign) 
        ] 
        public virtual HorizontalAlign HorizontalAlign {
            get { 
                if (ControlStyleCreated == false) {
                    return HorizontalAlign.NotSet;
                }
                return ((TableStyle)ControlStyle).HorizontalAlign; 
            }
            set { 
                ((TableStyle)ControlStyle).HorizontalAlign = value; 
            }
        } 


        protected bool Initialized {
            get { 
                return _inited;
            } 
        } 

 
        protected bool IsBoundUsingDataSourceID {
            get {
                return (DataSourceID.Length > 0);
            } 
        }
 
        public override bool SupportsDisabledAttribute { 
            get {
                return RenderingCompatibility < VersionUtil.Framework40; 
            }
        }

        protected bool RequiresDataBinding { 
            get {
                return _requiresDataBinding; 
            } 
            set {
                _requiresDataBinding = value; 
            }
        }

        protected DataSourceSelectArguments SelectArguments { 
            get {
                if (_arguments == null) { 
                    _arguments = CreateDataSourceSelectArguments(); 
                }
                return _arguments; 
            }
        }

 
        [
        DefaultValue(false), 
        WebCategory("Accessibility"), 
        WebSysDescription(SR.Table_UseAccessibleHeader)
        ] 
        public virtual bool UseAccessibleHeader {
            get {
                object b = ViewState["UseAccessibleHeader"];
                return (b != null) ? (bool)b : false; 
            }
            set { 
                ViewState["UseAccessibleHeader"] = value; 
            }
        } 


        /// 
        ///    Occurs when an item on the list is selected. 
        /// 
        [ 
        WebCategory("Action"), 
        WebSysDescription(SR.BaseDataList_OnSelectedIndexChanged)
        ] 
        public event EventHandler SelectedIndexChanged {
            add {
                Events.AddHandler(EventSelectedIndexChanged, value);
            } 
            remove {
                Events.RemoveHandler(EventSelectedIndexChanged, value); 
            } 
        }
 

        /// 
        ///     Not coded yet.
        ///  
        protected override void AddParsedSubObject(object obj) {
            return; 
        } 

        ///  
        /// Connects this data bound control to the appropriate DataSourceView
        /// and hooks up the appropriate event listener for the
        /// DataSourceViewChanged event. The return value is the new view (if
        /// any) that was connected to. An exception is thrown if there is 
        /// a problem finding the requested view or data source.
        ///  
        private DataSourceView ConnectToDataSourceView() { 
            if (_currentViewValid && !DesignMode) {
                // If the current view is correct, there is no need to reconnect 
                return _currentView;
            }

            // Disconnect from old view, if necessary 
            if ((_currentView != null) && (_currentViewIsFromDataSourceID)) {
                // We only care about this event if we are bound through the DataSourceID property 
                _currentView.DataSourceViewChanged -= new EventHandler(OnDataSourceViewChanged); 
            }
 
            // Connect to new view
            IDataSource ds = null;
            string dataSourceID = DataSourceID;
 
            if (dataSourceID.Length != 0) {
                // Try to find a DataSource control with the ID specified in DataSourceID 
                Control control = DataBoundControlHelper.FindControl(this, dataSourceID); 
                if (control == null) {
                    throw new HttpException(SR.GetString(SR.DataControl_DataSourceDoesntExist, ID, dataSourceID)); 
                }
                ds = control as IDataSource;
                if (ds == null) {
                    throw new HttpException(SR.GetString(SR.DataControl_DataSourceIDMustBeDataControl, ID, dataSourceID)); 
                }
            } 
 
            if (ds == null) {
                // DataSource control was not found, construct a temporary data source to wrap the data 
                ds = new ReadOnlyDataSource(DataSource, DataMember);
            }
            else {
                // Ensure that both DataSourceID as well as DataSource are not set at the same time 
                if (DataSource != null) {
                    throw new InvalidOperationException(SR.GetString(SR.DataControl_MultipleDataSources, ID)); 
                } 
            }
 
            // IDataSource was found, extract the appropriate view and return it
            DataSourceView newView = ds.GetView(DataMember);
            if (newView == null) {
                throw new InvalidOperationException(SR.GetString(SR.DataControl_ViewNotFound, ID)); 
            }
 
            _currentViewIsFromDataSourceID = IsBoundUsingDataSourceID; 
            _currentView = newView;
            if ((_currentView != null) && (_currentViewIsFromDataSourceID)) { 
                // We only care about this event if we are bound through the DataSourceID property
                _currentView.DataSourceViewChanged += new EventHandler(OnDataSourceViewChanged);
            }
            _currentViewValid = true; 

            return _currentView; 
        } 

 
        /// 
        /// 
        ///    Creates a child control using the view state.
        ///  
        protected internal override void CreateChildControls() {
            Controls.Clear(); 
 
            if (ViewState[ItemCountViewStateKey] == null) {
                if (RequiresDataBinding) { 
                    EnsureDataBound();
                }
            }
            else { 
                // create the control hierarchy using the view state (and
                // not the datasource) 
                CreateControlHierarchy(false); 
                ClearChildViewState();
            } 
        }


        protected abstract void CreateControlHierarchy(bool useDataSource); 

 
        public override void DataBind() { 
            // Don't databind to a data source control when the control is in the designer but not top-level
            if (IsBoundUsingDataSourceID && DesignMode && (Site == null)) { 
                return;
            }

            // do our own databinding 
            RequiresDataBinding = false;
            OnDataBinding(EventArgs.Empty); 
        } 

        protected virtual DataSourceSelectArguments CreateDataSourceSelectArguments() { 
            return DataSourceSelectArguments.Empty;
        }

 
        protected void EnsureDataBound() {
            try { 
                _throwOnDataPropertyChange = true; 
                if (RequiresDataBinding && DataSourceID.Length > 0) {
                    DataBind(); 
                }
            }
            finally {
                _throwOnDataPropertyChange = false; 
            }
        } 
 

        ///  
        /// Returns an IEnumerable that is the DataSource, which either came
        /// from the DataSource property or from the control bound via the
        /// DataSourceID property.
        ///  
        protected virtual IEnumerable GetData() {
            ConnectToDataSourceView(); 
 
            Debug.Assert(_currentViewValid);
 
            if (_currentView != null) {
                return _currentView.ExecuteSelect(SelectArguments);
            }
            return null; 
        }
 
 
        /// 
        ///    Determines if the specified data type can be bound to. 
        /// 
        public static bool IsBindableType(Type type) {
            return(type.IsPrimitive ||
                   (type == typeof(string)) || 
                   (type == typeof(DateTime)) ||
                   (type == typeof(Decimal))); 
        } 

 
        /// 
        /// 
        /// Raises the event of a 
        /// . 
        /// 
        protected override void OnDataBinding(EventArgs e) { 
            base.OnDataBinding(e); 

            // reset the control state 
            Controls.Clear();
            ClearChildViewState();

            // and create the control hierarchy using the datasource 
            dataKeysCollection = null;
            CreateControlHierarchy(true); 
            ChildControlsCreated = true; 

            TrackViewState(); 
        }


        ///  
        ///  This method is called when DataMember, DataSource, or DataSourceID is changed.
        ///  
        protected virtual void OnDataPropertyChanged() { 
            if (_throwOnDataPropertyChange) {
                throw new HttpException(SR.GetString(SR.DataBoundControl_InvalidDataPropertyChange, ID)); 
            }

            if (_inited) {
                RequiresDataBinding = true; 
            }
            _currentViewValid = false; 
        } 

 
        protected virtual void OnDataSourceViewChanged(object sender, EventArgs e) {
            RequiresDataBinding = true;
        }
 

        protected internal override void OnInit(EventArgs e) { 
            base.OnInit(e); 

            if (Page != null) { 
                Page.PreLoad += new EventHandler(this.OnPagePreLoad);

                if (!IsViewStateEnabled && Page.IsPostBack) {
                    RequiresDataBinding = true; 
                }
            } 
        } 

 
        protected internal override void OnLoad(EventArgs e) {
            _inited = true; // just in case we were added to the page after PreLoad
            ConnectToDataSourceView();
            if (Page != null &&  !_pagePreLoadFired && ViewState[ItemCountViewStateKey] == null) { 
                // If the control was added after PagePreLoad, we still need to databind it because it missed its
                // first change in PagePreLoad.  If this control was created by a call to a parent control's DataBind 
                // in Page_Load (with is relatively common), this control will already have been databound even 
                // though pagePreLoad never fired and the page isn't a postback.
                if (!Page.IsPostBack) { 
                    RequiresDataBinding = true;
                }

                // If the control was added to the page after page.PreLoad, we'll never get the event and we'll 
                // never databind the control.  So if we're catching up and Load happens but PreLoad never happened,
                // call DataBind.  This may make the control get databound twice if the user called DataBind on the control 
                // directly in Page.OnLoad, but better to bind twice than never to bind at all. 
                else if (IsViewStateEnabled) {
                    RequiresDataBinding = true; 
                }
            }

            base.OnLoad(e); 
        }
 
        private void OnPagePreLoad(object sender, EventArgs e) { 
            _inited = true;
 
            if (Page != null) {
                Page.PreLoad -= new EventHandler(this.OnPagePreLoad);

                // Setting RequiresDataBinding to true in OnLoad is too late because the OnLoad page event 
                // happens before the control.OnLoad method gets called.  So a page_load handler on the page
                // that calls DataBind won't prevent DataBind from getting called again in PreRender. 
                if (!Page.IsPostBack) { 
                    RequiresDataBinding = true;
                } 

                // If this is a postback and viewstate is enabled, but we have never bound the control
                // before, it is probably because its visibility was changed in the postback.  In this
                // case, we need to bind the control or it will never appear.  This is a common scenario 
                // for Wizard and MultiView.
                if (Page.IsPostBack && IsViewStateEnabled && ViewState[ItemCountViewStateKey] == null) { 
                    RequiresDataBinding = true; 
                }
            } 
            _pagePreLoadFired = true;
        }

 
        protected internal override void OnPreRender(EventArgs e) {
            EnsureDataBound(); 
            base.OnPreRender(e); 
        }
 

        /// 
        /// Raises the event of a .
        ///  
        protected virtual void OnSelectedIndexChanged(EventArgs e) {
            EventHandler handler = (EventHandler)Events[EventSelectedIndexChanged]; 
            if (handler != null) handler(this, e); 
        }
 

        protected internal abstract void PrepareControlHierarchy();

 
        /// 
        ///  
        ///    Displays the control on the client. 
        /// 
        protected internal override void Render(HtmlTextWriter writer) { 
            PrepareControlHierarchy();
            RenderContents(writer);
        }
    } 
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

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