ForeignKeyConstraint.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Data / System / Data / ForeignKeyConstraint.cs / 1305376 / ForeignKeyConstraint.cs

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

namespace System.Data { 
    using System;
    using System.ComponentModel;
    using System.Diagnostics;
    using System.Data.Common; 

    ///  
    ///    Represents an action 
    ///       restriction enforced on a set of columns in a primary key/foreign key relationship when
    ///       a value or row is either deleted or updated. 
    /// 
    [
    DefaultProperty("ConstraintName"),
    Editor("Microsoft.VSDesigner.Data.Design.ForeignKeyConstraintEditor, " + AssemblyRef.MicrosoftVSDesigner, "System.Drawing.Design.UITypeEditor, " + AssemblyRef.SystemDrawing), 
    ]
    public class ForeignKeyConstraint : Constraint { 
        // constants 
        internal const Rule                   Rule_Default                   = Rule.Cascade;
        internal const AcceptRejectRule       AcceptRejectRule_Default       = AcceptRejectRule.None; 

        // properties
        internal Rule deleteRule = Rule_Default;
        internal Rule updateRule = Rule_Default; 
        internal AcceptRejectRule acceptRejectRule = AcceptRejectRule_Default;
        private DataKey childKey; 
        private DataKey parentKey; 

        // Design time serialization 
        internal string constraintName = null;
        internal string[] parentColumnNames = null;
        internal string[] childColumnNames = null;
        internal string parentTableName = null; 
        internal string parentTableNamespace = null;
 
        ///  
        ///    
        ///       Initializes a new instance of the  class with the specified parent and 
        ///       child  objects.
        ///    
        /// 
        public ForeignKeyConstraint(DataColumn parentColumn, DataColumn childColumn) 
        : this(null, parentColumn, childColumn) {
        } 
 
        /// 
        ///     
        ///       Initializes a new instance of the  class with the specified name,
        ///       parent and child  objects.
        ///    
        ///  
        public ForeignKeyConstraint(string constraintName, DataColumn parentColumn, DataColumn childColumn) {
            DataColumn[] parentColumns = new DataColumn[] {parentColumn}; 
            DataColumn[] childColumns = new DataColumn[] {childColumn}; 
            Create(constraintName, parentColumns, childColumns);
        } 

        /// 
        ///    
        ///       Initializes a new instance of the  class with the specified arrays 
        ///       of parent and child  objects.
        ///     
        ///  
        public ForeignKeyConstraint(DataColumn[] parentColumns, DataColumn[] childColumns)
        : this(null, parentColumns, childColumns) { 
        }

        /// 
        ///     
        ///       Initializes a new instance of the  class with the specified name,
        ///       and arrays of parent and child  objects. 
        ///     
        /// 
        public ForeignKeyConstraint(string constraintName, DataColumn[] parentColumns, DataColumn[] childColumns) { 
            Create(constraintName, parentColumns, childColumns);
        }

        // construct design time object 
        /// 
        ///    [To be supplied.] 
        ///  
        [Browsable(false)]
        public ForeignKeyConstraint(string constraintName, string parentTableName, string[] parentColumnNames, string[] childColumnNames, 
                                    AcceptRejectRule acceptRejectRule, Rule deleteRule, Rule updateRule) {
            this.constraintName = constraintName;
            this.parentColumnNames = parentColumnNames;
            this.childColumnNames = childColumnNames; 
            this.parentTableName = parentTableName;
            this.acceptRejectRule = acceptRejectRule; 
            this.deleteRule = deleteRule; 
            this.updateRule = updateRule;
//            ForeignKeyConstraint(constraintName, parentTableName, null, parentColumnNames, childColumnNames,acceptRejectRule, deleteRule, updateRule) 
        }


        // construct design time object 
        [Browsable(false)]
        public ForeignKeyConstraint(string constraintName, string parentTableName, string parentTableNamespace, string[] parentColumnNames, 
                                    string[] childColumnNames, AcceptRejectRule acceptRejectRule, Rule deleteRule, Rule updateRule) { 
            this.constraintName = constraintName;
            this.parentColumnNames = parentColumnNames; 
            this.childColumnNames = childColumnNames;
            this.parentTableName = parentTableName;
            this.parentTableNamespace= parentTableNamespace;
            this.acceptRejectRule = acceptRejectRule; 
            this.deleteRule = deleteRule;
            this.updateRule = updateRule; 
        } 

        ///  
        /// The internal constraint object for the child table.
        /// 
        internal DataKey ChildKey {
            get { 
                CheckStateForProperty();
                return childKey; 
            } 
        }
 
        /// 
        ///    
        ///       Gets the child columns of this constraint.
        ///     
        /// 
        [ 
        ResCategoryAttribute(Res.DataCategory_Data), 
        ResDescriptionAttribute(Res.ForeignKeyConstraintChildColumnsDescr),
        ReadOnly(true) 
        ]
        public virtual DataColumn[] Columns {
            get {
                CheckStateForProperty(); 
                return childKey.ToArray();
            } 
        } 

        ///  
        ///    
        ///       Gets the child table of this constraint.
        ///    
        ///  
        [
        ResCategoryAttribute(Res.DataCategory_Data), 
        ResDescriptionAttribute(Res.ConstraintTableDescr), 
        ReadOnly(true)
        ] 
        public override DataTable Table {
            get {
                CheckStateForProperty();
                return childKey.Table; 
            }
        } 
 
        internal string[] ParentColumnNames {
            get { 
                return parentKey.GetColumnNames();
            }
        }
 
        internal string[] ChildColumnNames {
            get { 
                return childKey.GetColumnNames(); 
            }
        } 

        internal override void CheckCanAddToCollection(ConstraintCollection constraints) {
            if (Table != constraints.Table)
                throw ExceptionBuilder.ConstraintAddFailed(constraints.Table); 
            if (Table.Locale.LCID != RelatedTable.Locale.LCID || Table.CaseSensitive != RelatedTable.CaseSensitive)
                throw ExceptionBuilder.CaseLocaleMismatch(); 
        } 

        internal override bool CanBeRemovedFromCollection(ConstraintCollection constraints, bool fThrowException) { 
            return true;
        }

        internal bool IsKeyNull( object[] values ) { 
            for (int i = 0; i < values.Length; i++) {
            	if (! DataStorage.IsObjectNull(values[i])) 
                    return false; 
            }
 
            return true;
        }

        internal override bool IsConstraintViolated() { 
            Index childIndex = childKey.GetSortIndex();
            object[] uniqueChildKeys = childIndex.GetUniqueKeyValues(); 
            bool errors = false; 

            Index parentIndex = parentKey.GetSortIndex(); 
            for (int i = 0; i < uniqueChildKeys.Length; i++) {
                object[] childValues = (object[]) uniqueChildKeys[i];

                if (!IsKeyNull(childValues)) { 
                    if (!parentIndex.IsKeyInIndex(childValues)) {
                        DataRow[] rows = childIndex.GetRows(childIndex.FindRecords(childValues)); 
                        string error = Res.GetString(Res.DataConstraint_ForeignKeyViolation, ConstraintName, ExceptionBuilder.KeysToString(childValues)); 
                        for (int j = 0; j < rows.Length; j++) {
                            rows[j].RowError = error; 
                        }
                        errors = true;
                    }
                } 
            }
            return errors; 
        } 

        internal override bool CanEnableConstraint() { 
            if (Table.DataSet == null || !Table.DataSet.EnforceConstraints)
                return true;

            Index childIndex = childKey.GetSortIndex(); 
            object[] uniqueChildKeys = childIndex.GetUniqueKeyValues();
 
            Index parentIndex = parentKey.GetSortIndex(); 
            for (int i = 0; i < uniqueChildKeys.Length; i++) {
                object[] childValues = (object[]) uniqueChildKeys[i]; 

                if (!IsKeyNull(childValues) && !parentIndex.IsKeyInIndex(childValues)) {
                    return false;
                } 
            }
            return true; 
        } 

        internal void CascadeCommit(DataRow row) { 
            if (row.RowState == DataRowState.Detached)
                return;
            if (acceptRejectRule == AcceptRejectRule.Cascade) {
                Index childIndex = childKey.GetSortIndex(      row.RowState == DataRowState.Deleted ? DataViewRowState.Deleted : DataViewRowState.CurrentRows ); 
                object[] key     = row.GetKeyValues(parentKey, row.RowState == DataRowState.Deleted ? DataRowVersion.Original  : DataRowVersion.Default       );
                if (IsKeyNull(key)) { 
                    return; 
                }
 
                Range range      = childIndex.FindRecords(key);
                if (!range.IsNull) {
                    // SQLBU 499726 - DataTable internal index is corrupted: '13'
                    // Self-referencing table has suspendIndexEvents, in the multi-table scenario the child table hasn't 
                    // this allows the self-ref table to maintain the index while in the child-table doesn't
                    DataRow[] rows = childIndex.GetRows(range); 
                    foreach(DataRow childRow in rows) { 
                        if (DataRowState.Detached != childRow.RowState) {
                            if (childRow.inCascade) 
                                continue;
                            childRow.AcceptChanges();
                        }
                    } 
                }
            } 
        } 

        internal void CascadeDelete(DataRow row) { 
            if (-1 == row.newRecord)
                return;

            object[] currentKey = row.GetKeyValues(parentKey, DataRowVersion.Current); 
            if (IsKeyNull(currentKey)) {
                return; 
            } 

            Index childIndex = childKey.GetSortIndex(); 
            switch (DeleteRule) {
            case Rule.None: {
                    if (row.Table.DataSet.EnforceConstraints) {
                        // if we're not cascading deletes, we should throw if we're going to strand a child row under enforceConstraints. 
                        Range range = childIndex.FindRecords(currentKey);
                        if (!range.IsNull) { 
                            if (range.Count == 1 && childIndex.GetRow(range.Min) == row) 
                                return;
 
                            throw ExceptionBuilder.FailedCascadeDelete(ConstraintName);
                        }
                    }
                    break; 
                }
 
            case Rule.Cascade: { 
                    object[] key = row.GetKeyValues(parentKey, DataRowVersion.Default);
                    Range range = childIndex.FindRecords(key); 
                    if (!range.IsNull) {
                        DataRow[] rows = childIndex.GetRows(range);

                        for (int j = 0; j < rows.Length; j++) { 
                            DataRow r = rows[j];
                            if (r.inCascade) 
                                continue; 
                            r.Table.DeleteRow(r);
                        } 
                    }
                    break;
                }
 
            case Rule.SetNull: {
                    object[] proposedKey = new object[childKey.ColumnsReference.Length]; 
                    for (int i = 0; i < childKey.ColumnsReference.Length; i++) 
                        proposedKey[i] = DBNull.Value;
                    Range range = childIndex.FindRecords(currentKey); 
                    if (!range.IsNull) {
                        DataRow[] rows = childIndex.GetRows(range);
                        for (int j = 0; j < rows.Length; j++) {
                            // if (rows[j].inCascade) 
                            //    continue;
                            if (row != rows[j]) 
                                rows[j].SetKeyValues(childKey, proposedKey); 
                        }
                    } 
                    break;
                }
            case Rule.SetDefault: {
                    object[] proposedKey = new object[childKey.ColumnsReference.Length]; 
                    for (int i = 0; i < childKey.ColumnsReference.Length; i++)
                        proposedKey[i] = childKey.ColumnsReference[i].DefaultValue; 
                    Range range = childIndex.FindRecords(currentKey); 
                    if (!range.IsNull) {
                        DataRow[] rows = childIndex.GetRows(range); 
                        for (int j = 0; j < rows.Length; j++) {
                            // if (rows[j].inCascade)
                            //    continue;
                            if (row != rows[j]) 
                                rows[j].SetKeyValues(childKey, proposedKey);
                        } 
                    } 
                    break;
                } 
            default: {
                    Debug.Assert(false, "Unknown Rule value");
 			break;
                } 
            }
        } 
 
        internal void CascadeRollback(DataRow row) {
            Index childIndex = childKey.GetSortIndex(      row.RowState == DataRowState.Deleted  ? DataViewRowState.OriginalRows : DataViewRowState.CurrentRows); 
            object[] key     = row.GetKeyValues(parentKey, row.RowState == DataRowState.Modified ? DataRowVersion.Current        : DataRowVersion.Default      );

            // Bug : This is definitely not a proper fix. (Ref. MDAC Bug 73592)
            if (IsKeyNull(key)) { 
                return;
            } 
 
            Range range      = childIndex.FindRecords(key);
            if (acceptRejectRule == AcceptRejectRule.Cascade) { 
                if (!range.IsNull) {
                    DataRow[] rows = childIndex.GetRows(range);
                    for (int j = 0; j < rows.Length; j++) {
                        if (rows[j].inCascade) 
                            continue;
                        rows[j].RejectChanges(); 
                    } 
                }
            } 
            else {
                // AcceptRejectRule.None
                if (row.RowState != DataRowState.Deleted && row.Table.DataSet.EnforceConstraints) {
                    if (!range.IsNull) { 
                        if (range.Count == 1 && childIndex.GetRow(range.Min) == row)
                            return; 
 
                        if (row.HasKeyChanged(parentKey)) {// if key is not changed, this will not cause child to be stranded
                            throw ExceptionBuilder.FailedCascadeUpdate(ConstraintName); 
                        }
                    }
                }
            } 
        }
 
        internal void CascadeUpdate(DataRow row) { 
            if (-1 == row.newRecord)
                return; 

            object[] currentKey = row.GetKeyValues(parentKey, DataRowVersion.Current);
            if (!Table.DataSet.fInReadXml && IsKeyNull(currentKey)) {
                return; 
            }
 
            Index childIndex = childKey.GetSortIndex(); 
            switch (UpdateRule) {
            case Rule.None: { 
                    if (row.Table.DataSet.EnforceConstraints)
                    {
                        // if we're not cascading deletes, we should throw if we're going to strand a child row under enforceConstraints.
                        Range range = childIndex.FindRecords(currentKey); 
                        if (!range.IsNull) {
                            throw ExceptionBuilder.FailedCascadeUpdate(ConstraintName); 
                        } 
                    }
                    break; 
                }

            case Rule.Cascade: {
                    Range range = childIndex.FindRecords(currentKey); 
                    if (!range.IsNull) {
                        object[] proposedKey = row.GetKeyValues(parentKey, DataRowVersion.Proposed); 
                        DataRow[] rows = childIndex.GetRows(range); 
                        for (int j = 0; j < rows.Length; j++) {
                            // if (rows[j].inCascade) 
                            //    continue;
                            rows[j].SetKeyValues(childKey, proposedKey);
                        }
                    } 
                    break;
                } 
 
            case Rule.SetNull: {
                    object[] proposedKey = new object[childKey.ColumnsReference.Length]; 
                    for (int i = 0; i < childKey.ColumnsReference.Length; i++)
                        proposedKey[i] = DBNull.Value;
                    Range range = childIndex.FindRecords(currentKey);
                    if (!range.IsNull) { 
                        DataRow[] rows = childIndex.GetRows(range);
                        for (int j = 0; j < rows.Length; j++) { 
                            // if (rows[j].inCascade) 
                            //    continue;
                            rows[j].SetKeyValues(childKey, proposedKey); 
                        }
                    }
                    break;
                } 
            case Rule.SetDefault: {
                    object[] proposedKey = new object[childKey.ColumnsReference.Length]; 
                    for (int i = 0; i < childKey.ColumnsReference.Length; i++) 
                        proposedKey[i] = childKey.ColumnsReference[i].DefaultValue;
                    Range range = childIndex.FindRecords(currentKey); 
                    if (!range.IsNull) {
                        DataRow[] rows = childIndex.GetRows(range);
                        for (int j = 0; j < rows.Length; j++) {
                            // if (rows[j].inCascade) 
                            //    continue;
                            rows[j].SetKeyValues(childKey, proposedKey); 
                        } 
                    }
                    break; 
                }
            default: {
                    Debug.Assert(false, "Unknown Rule value");
		    break; 
                }
            } 
        } 

        internal void CheckCanClearParentTable(DataTable table) { 
            if (Table.DataSet.EnforceConstraints && Table.Rows.Count > 0) {
                throw ExceptionBuilder.FailedClearParentTable(table.TableName, ConstraintName, Table.TableName);
            }
        } 

        internal void CheckCanRemoveParentRow(DataRow row) { 
            Debug.Assert(Table.DataSet != null, "Relation " + ConstraintName + " isn't part of a DataSet, so this check shouldn't be happening."); 
            if (!Table.DataSet.EnforceConstraints)
                return; 
            if (DataRelation.GetChildRows(this.ParentKey, this.ChildKey, row, DataRowVersion.Default).Length > 0) {
                throw ExceptionBuilder.RemoveParentRow(this);
            }
        } 

        internal void CheckCascade(DataRow row, DataRowAction action) { 
            Debug.Assert(Table.DataSet != null, "ForeignKeyConstraint " + ConstraintName + " isn't part of a DataSet, so this check shouldn't be happening."); 

            if (row.inCascade) 
                return;

            row.inCascade = true;
            try { 
                if (action == DataRowAction.Change) {
                    if (row.HasKeyChanged(parentKey)) { 
                        CascadeUpdate(row); 
                    }
                } 
                else if (action == DataRowAction.Delete) {
                    CascadeDelete(row);
                }
                else if (action == DataRowAction.Commit) { 
                    CascadeCommit(row);
                } 
                else if (action == DataRowAction.Rollback) { 
                    CascadeRollback(row);
                 } 
                else if (action == DataRowAction.Add) {
                }
                else {
                    Debug.Assert(false, "attempt to cascade unknown action: " + ((Enum) action).ToString()); 
                }
            } 
            finally { 
                row.inCascade = false;
            } 
        }

        internal override void CheckConstraint(DataRow childRow, DataRowAction action) {
            if ((action == DataRowAction.Change || 
                 action == DataRowAction.Add ||
                 action == DataRowAction.Rollback) && 
                Table.DataSet != null && Table.DataSet.EnforceConstraints && 
                childRow.HasKeyChanged(childKey)) {
 
                // This branch is for cascading case verification.
                DataRowVersion version = (action == DataRowAction.Rollback) ? DataRowVersion.Original : DataRowVersion.Current;
                object[] childKeyValues = childRow.GetKeyValues(childKey);
                // check to see if this is just a change to my parent's proposed value. 
                if (childRow.HasVersion(version)) {
                    // this is the new proposed value for the parent. 
                    DataRow parentRow = DataRelation.GetParentRow(this.ParentKey, this.ChildKey, childRow, version); 
                    if(parentRow != null && parentRow.inCascade) {
                        object[] parentKeyValues = parentRow.GetKeyValues(parentKey, action == DataRowAction.Rollback ? version : DataRowVersion.Default); 

                        int parentKeyValuesRecord = childRow.Table.NewRecord();
                        childRow.Table.SetKeyValues(childKey, parentKeyValues, parentKeyValuesRecord);
                        if (childKey.RecordsEqual(childRow.tempRecord, parentKeyValuesRecord)) { 
                            return;
                        } 
                    } 
                }
 
                // now check to see if someone exists... it will have to be in a parent row's current, not a proposed.
                object[] childValues = childRow.GetKeyValues(childKey);
                if (!IsKeyNull(childValues)) {
                    Index parentIndex = parentKey.GetSortIndex(); 
                    if (!parentIndex.IsKeyInIndex(childValues)) {
                        // could be self-join constraint 
                        if (childKey.Table == parentKey.Table && childRow.tempRecord != -1) { 
                            int lo = 0;
                            for (lo = 0; lo < childValues.Length; lo++) { 
                                DataColumn column = parentKey.ColumnsReference[lo];
                                object value = column.ConvertValue(childValues[lo]);
                                if (0 != column.CompareValueTo(childRow.tempRecord, value)) {
                                    break; 
                                }
                            } 
                            if (lo == childValues.Length) { 
                                return;
                            } 
                        }
                        throw ExceptionBuilder.ForeignKeyViolation(ConstraintName, childKeyValues);
                    }
                } 
            }
        } 
 
        private void NonVirtualCheckState () {
            if (_DataSet == null) { 
                // Make sure columns arrays are valid
                parentKey.CheckState();
                childKey.CheckState();
 
                if (parentKey.Table.DataSet != childKey.Table.DataSet) {
                    throw ExceptionBuilder.TablesInDifferentSets(); 
                } 

                for (int i = 0; i < parentKey.ColumnsReference.Length; i++) { 
                    if (parentKey.ColumnsReference[i].DataType != childKey.ColumnsReference[i].DataType ||
                        ((parentKey.ColumnsReference[i].DataType ==  typeof(DateTime)) && (parentKey.ColumnsReference[i].DateTimeMode != childKey.ColumnsReference[i].DateTimeMode) && ((parentKey.ColumnsReference[i].DateTimeMode & childKey.ColumnsReference[i].DateTimeMode) != DataSetDateTime.Unspecified)))
                        throw ExceptionBuilder.ColumnsTypeMismatch();
                } 

                if (childKey.ColumnsEqual(parentKey)) { 
                    throw ExceptionBuilder.KeyColumnsIdentical(); 
                }
            } 
        }

        // If we're not in a DataSet relations collection, we need to verify on every property get that we're
        // still a good relation object. 
        internal override void CheckState() {
            NonVirtualCheckState (); 
        } 

        ///  
        ///    
        ///       Indicates what kind of action should take place across
        ///       this constraint when 
        ///       is invoked. 
        ///    
        ///  
        [ 
        ResCategoryAttribute(Res.DataCategory_Data),
        DefaultValue(AcceptRejectRule_Default), 
        ResDescriptionAttribute(Res.ForeignKeyConstraintAcceptRejectRuleDescr)
        ]
        public virtual AcceptRejectRule AcceptRejectRule {
            get { 
                CheckStateForProperty();
                return acceptRejectRule; 
            } 
            set {
                switch(value) { // @perfnote: Enum.IsDefined 
                case AcceptRejectRule.None:
                case AcceptRejectRule.Cascade:
                    this.acceptRejectRule = value;
                    break; 
                default:
                    throw Common.ADP.InvalidAcceptRejectRule(value); 
                } 
            }
        } 

        internal override bool ContainsColumn(DataColumn column) {
            return parentKey.ContainsColumn(column) || childKey.ContainsColumn(column);
        } 

        internal override Constraint Clone(DataSet destination) { 
            return Clone(destination, false); 
        }
 
        internal override Constraint Clone(DataSet destination, bool ignorNSforTableLookup) {
            int iDest;
            if (ignorNSforTableLookup) {
                iDest = destination.Tables.IndexOf(Table.TableName); 
            }
            else { 
                iDest = destination.Tables.IndexOf(Table.TableName, Table.Namespace, false); // pass false for last param 
                // to be backward compatable, otherwise meay cause new exception
            } 

            if (iDest < 0)
                return null;
            DataTable table = destination.Tables[iDest]; 
            if (ignorNSforTableLookup) {
                iDest = destination.Tables.IndexOf(RelatedTable.TableName); 
            } 
            else {
                iDest = destination.Tables.IndexOf(RelatedTable.TableName, RelatedTable.Namespace, false);// pass false for last param 
            }
            if (iDest < 0)
                return null;
            DataTable relatedTable = destination.Tables[iDest]; 

            int keys = Columns.Length; 
            DataColumn[] columns = new DataColumn[keys]; 
            DataColumn[] relatedColumns = new DataColumn[keys];
 
            for (int i = 0; i < keys; i++) {
                DataColumn src = Columns[i];
                iDest = table.Columns.IndexOf(src.ColumnName);
                if (iDest < 0) 
                    return null;
                columns[i] = table.Columns[iDest]; 
 
                src = RelatedColumnsReference[i];
                iDest = relatedTable.Columns.IndexOf(src.ColumnName); 
                if (iDest < 0)
                    return null;
                relatedColumns[i] = relatedTable.Columns[iDest];
            } 
            ForeignKeyConstraint clone = new ForeignKeyConstraint(ConstraintName,relatedColumns, columns);
            clone.UpdateRule = this.UpdateRule; 
            clone.DeleteRule = this.DeleteRule; 
            clone.AcceptRejectRule = this.AcceptRejectRule;
 
            // ...Extended Properties
            foreach(Object key in this.ExtendedProperties.Keys) {
                clone.ExtendedProperties[key]=this.ExtendedProperties[key];
            } 

            return clone; 
        } 

 
        internal ForeignKeyConstraint Clone(DataTable destination) {
            Debug.Assert(this.Table == this.RelatedTable, "We call this clone just if we have the same datatable as parent and child ");
            int keys = Columns.Length;
            DataColumn[] columns = new DataColumn[keys]; 
            DataColumn[] relatedColumns = new DataColumn[keys];
 
            int iDest  =0; 

            for (int i = 0; i < keys; i++) { 
                DataColumn src = Columns[i];
                iDest = destination.Columns.IndexOf(src.ColumnName);
                if (iDest < 0)
                    return null; 
                columns[i] = destination.Columns[iDest];
 
                src = RelatedColumnsReference[i]; 
                iDest = destination.Columns.IndexOf(src.ColumnName);
                if (iDest < 0) 
                    return null;
                relatedColumns[i] = destination.Columns[iDest];
            }
            ForeignKeyConstraint clone = new ForeignKeyConstraint(ConstraintName, relatedColumns, columns); 
            clone.UpdateRule = this.UpdateRule;
            clone.DeleteRule = this.DeleteRule; 
            clone.AcceptRejectRule = this.AcceptRejectRule; 

            // ...Extended Properties 
            foreach(Object key in this.ExtendedProperties.Keys) {
                clone.ExtendedProperties[key]=this.ExtendedProperties[key];
            }
 
            return clone;
        } 
 

 
        private void Create(string relationName, DataColumn[] parentColumns, DataColumn[] childColumns) {
            if (parentColumns.Length == 0 || childColumns.Length == 0)
                throw ExceptionBuilder.KeyLengthZero();
 
            if (parentColumns.Length != childColumns.Length)
                throw ExceptionBuilder.KeyLengthMismatch(); 
 
            for (int i = 0; i < parentColumns.Length; i++) {
                if (parentColumns[i].Computed) { 
                    throw ExceptionBuilder.ExpressionInConstraint(parentColumns[i]);
                }
                if (childColumns[i].Computed) {
                    throw ExceptionBuilder.ExpressionInConstraint(childColumns[i]); 
                }
            } 
 
            this.parentKey = new DataKey(parentColumns, true);
            this.childKey = new DataKey(childColumns, true); 

            ConstraintName = relationName;

            NonVirtualCheckState(); 
        }
 
        ///  
        ///     Gets
        ///       or sets the action that occurs across this constraint when a row is deleted. 
        /// 
        [
        ResCategoryAttribute(Res.DataCategory_Data),
        DefaultValue(Rule_Default), 
        ResDescriptionAttribute(Res.ForeignKeyConstraintDeleteRuleDescr)
        ] 
        public virtual Rule DeleteRule { 
            get {
                CheckStateForProperty(); 
                return deleteRule;
            }
            set {
                switch(value) { // @perfnote: Enum.IsDefined 
                case Rule.None:
                case Rule.Cascade: 
                case Rule.SetNull: 
                case Rule.SetDefault:
                    this.deleteRule = value; 
                    break;
                default:
                    throw Common.ADP.InvalidRule(value);
                } 
            }
        } 
 
        /// 
        /// Gets a value indicating whether the current  is identical to the specified object. 
        /// 
        public override bool Equals(object key) {
            if (!(key is ForeignKeyConstraint))
                return false; 
            ForeignKeyConstraint key2 = (ForeignKeyConstraint) key;
 
            // The ParentKey and ChildKey completely identify the ForeignKeyConstraint 
            return this.ParentKey.ColumnsEqual(key2.ParentKey) && this.ChildKey.ColumnsEqual(key2.ChildKey);
        } 

        /// 
        ///    [To be supplied.]
        ///  
        public override Int32 GetHashCode() {
            return base.GetHashCode(); 
        } 

        ///  
        ///    
        ///       The parent columns of this constraint.
        ///    
        ///  
        [
        ResCategoryAttribute(Res.DataCategory_Data), 
        ResDescriptionAttribute(Res.ForeignKeyConstraintParentColumnsDescr), 
        ReadOnly(true)
        ] 
        public virtual DataColumn[] RelatedColumns {
            get {
                CheckStateForProperty();
                return parentKey.ToArray(); 
            }
        } 
 
        internal DataColumn[] RelatedColumnsReference {
            get { 
                CheckStateForProperty();
                return parentKey.ColumnsReference;
            }
        } 

        ///  
        /// The internal key object for the parent table. 
        /// 
        internal DataKey ParentKey { 
            get {
                CheckStateForProperty();
                return parentKey;
            } 
        }
 
        internal DataRelation FindParentRelation () { 
            DataRelationCollection rels = Table.ParentRelations;
 
            for (int i = 0; i < rels.Count; i++) {
                if (rels[i].ChildKeyConstraint == this)
                    return rels[i];
            } 
            return null;
        } 
 
        /// 
        ///     
        ///       Gets the parent table of this constraint.
        ///    
        /// 
        [ 
        ResCategoryAttribute(Res.DataCategory_Data),
        ResDescriptionAttribute(Res.ForeignKeyRelatedTableDescr), 
        ReadOnly(true) 
        ]
        public virtual DataTable RelatedTable { 
            get {
                CheckStateForProperty();
                return parentKey.Table;
            } 
        }
 
        ///  
        ///    Gets or
        ///       sets the action that occurs across this constraint on when a row is 
        ///       updated.
        /// 
        [
        ResCategoryAttribute(Res.DataCategory_Data), 
        DefaultValue(Rule_Default),
        ResDescriptionAttribute(Res.ForeignKeyConstraintUpdateRuleDescr) 
        ] 
        public virtual Rule UpdateRule {
            get { 
                CheckStateForProperty();
                return updateRule;
            }
            set { 
                switch(value) { // @perfnote: Enum.IsDefined
                case Rule.None: 
                case Rule.Cascade: 
                case Rule.SetNull:
                case Rule.SetDefault: 
                    this.updateRule = value;
                    break;
                default:
                    throw Common.ADP.InvalidRule(value); 
                }
            } 
        } 
    }
} 

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

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