XmlCharCheckingWriter.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ Dotnetfx_Win7_3.5.1 / Dotnetfx_Win7_3.5.1 / 3.5.1 / DEVDIV / depot / DevDiv / releases / whidbey / NetFXspW7 / ndp / fx / src / Xml / System / Xml / Core / XmlCharCheckingWriter.cs / 1 / XmlCharCheckingWriter.cs

                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
using System; 
using System.IO;
using System.Text; 
using System.Xml.XPath;
using System.Xml.Schema;
using System.Collections;
using System.Diagnostics; 

namespace System.Xml { 
 
    //
    // XmlCharCheckingWriter 
    //
    internal class XmlCharCheckingWriter : XmlWrappingWriter {
//
// Fields 
//
        bool checkValues; 
        bool checkNames; 
        bool replaceNewLines;
        string newLineChars; 

        XmlCharType xmlCharType;
//
// Constructor 
//
        internal XmlCharCheckingWriter( XmlWriter baseWriter, bool checkValues, bool checkNames, bool replaceNewLines, string newLineChars ) 
            : base( baseWriter ) { 

            Debug.Assert( checkValues || replaceNewLines ); 
            this.checkValues = checkValues;
            this.checkNames = checkNames;
            this.replaceNewLines = replaceNewLines;
            this.newLineChars = newLineChars; 

            if ( checkValues ) { 
                xmlCharType = XmlCharType.Instance; 
            }
        } 

//
// XmlWriter implementation
// 

        public override XmlWriterSettings Settings { 
            get { 
                XmlWriterSettings s = base.writer.Settings;
                if ( s == null ) { 
                    s = new XmlWriterSettings();
                }
                else {
                    s = s.Clone(); 
                }
                if ( checkValues ) { 
                    s.CheckCharacters = true; 
                }
                if ( replaceNewLines ) { 
                    s.NewLineHandling = NewLineHandling.Replace;
                    s.NewLineChars = newLineChars;
                }
                s.ReadOnly = true; 
                return s;
            } 
        } 

        public override void WriteDocType( string name, string pubid, string sysid, string subset ) { 
            if ( checkNames ) {
                ValidateQName( name );
            }
            if ( checkValues ) { 
                if ( pubid != null ) {
                    int i; 
                    if ( ( i = xmlCharType.IsPublicId( pubid ) ) >= 0 ) { 
                        throw XmlConvert.CreateInvalidCharException( pubid[i] );
                    } 
                }
                if ( sysid != null ) {
                    CheckCharacters( sysid );
                } 
                if ( subset != null ) {
                    CheckCharacters( subset ); 
                } 
            }
            if ( replaceNewLines ) { 
                sysid = ReplaceNewLines( sysid );
                pubid = ReplaceNewLines( pubid );
                subset = ReplaceNewLines( subset );
            } 
            writer.WriteDocType( name, pubid, sysid, subset );
        } 
 
        public override void WriteStartElement( string prefix, string localName, string ns ) {
            if ( checkNames ) { 
                if ( localName == null || localName.Length == 0 ) {
                    throw new ArgumentException( Res.GetString( Res.Xml_EmptyLocalName ) );
                }
                ValidateNCName( localName ); 

                if ( prefix != null && prefix.Length > 0 ) { 
                    ValidateNCName( prefix ); 
                }
            } 
            writer.WriteStartElement( prefix, localName, ns );
        }

        public override void WriteStartAttribute( string prefix, string localName, string ns ) { 
            if ( checkNames ) {
                if ( localName == null || localName.Length == 0 ) { 
                    throw new ArgumentException( Res.GetString( Res.Xml_EmptyLocalName ) ); 
                }
                ValidateNCName( localName ); 

                if ( prefix != null && prefix.Length > 0 ) {
                    ValidateNCName( prefix );
                } 
            }
            writer.WriteStartAttribute( prefix, localName, ns ); 
        } 

        public override void WriteCData( string text ) { 
            if ( text != null ) {
                if ( checkValues ) {
                    CheckCharacters( text );
                } 
                if ( replaceNewLines ) {
                    text = ReplaceNewLines( text ); 
                } 
                int i;
                while ( ( i = text.IndexOf( "]]>", StringComparison.Ordinal ) ) >= 0 ) { 
                    writer.WriteCData( text.Substring( 0, i + 2 ) );
                    text = text.Substring( i + 2 );
                }
            } 
            writer.WriteCData( text );
        } 
 
        public override void WriteComment( string text ) {
            if ( text != null ) { 
                if ( checkValues ) {
                    CheckCharacters( text );
                    text = InterleaveInvalidChars( text, '-', '-' );
                } 
                if ( replaceNewLines ) {
                    text = ReplaceNewLines( text ); 
                } 
            }
            writer.WriteComment( text ); 
        }

        public override void WriteProcessingInstruction( string name, string text ) {
            if ( checkNames ) { 
                ValidateNCName( name );
            } 
            if ( text != null ) { 
                if ( checkValues ) {
                    CheckCharacters( text ); 
                    text = InterleaveInvalidChars( text, '?', '>' );
                }
                if ( replaceNewLines ) {
                    text = ReplaceNewLines( text ); 
                }
            } 
            writer.WriteProcessingInstruction( name, text ); 
        }
 
        public override void WriteEntityRef( string name ) {
            if ( checkNames ) {
                ValidateQName( name );
            } 
            writer.WriteEntityRef( name );
        } 
 
        public override void WriteWhitespace( string ws ) {
            // "checkNames" is intentional here; if false, the whitespaces are checked in XmlWellformedWriter 
            if ( checkNames ) {
                int i;
                if ( ( i = xmlCharType.IsOnlyWhitespaceWithPos( ws ) ) != -1 ) {
                    throw new ArgumentException( Res.GetString( Res.Xml_InvalidWhitespaceCharacter, XmlException.BuildCharExceptionStr( ws[i] ) ) ); 
                }
            } 
            writer.WriteWhitespace( ws ); 
        }
 
        public override void WriteString( string text ) {
            if ( text != null ) {
                if ( checkValues ) {
                    CheckCharacters( text ); 
                }
                if ( replaceNewLines && WriteState != WriteState.Attribute ) { 
                    text = ReplaceNewLines( text ); 
                }
            } 
            writer.WriteString( text );
        }

        public override void WriteSurrogateCharEntity( char lowChar, char highChar ) { 
            writer.WriteSurrogateCharEntity( lowChar, highChar );
        } 
 
        public override void WriteChars( char[] buffer, int index, int count ) {
            if ( checkValues ) { 
                CheckCharacters( buffer, index, count );
            }
            if ( replaceNewLines && WriteState != WriteState.Attribute ) {
                string text = ReplaceNewLines( buffer, index, count ); 
                if ( text != null ) {
                    WriteString( text ); 
                    return; 
                }
            } 
            writer.WriteChars( buffer, index, count );
        }

        public override void WriteNmToken( string name ) { 
            if ( checkNames ) {
                if ( name == null || name.Length == 0 ) { 
                    throw new ArgumentException( Res.GetString( Res.Xml_EmptyName ) ); 
                }
                XmlConvert.VerifyNMTOKEN( name ); 
            }
            writer.WriteNmToken( name );
        }
 
        public override void WriteName( string name ) {
            if ( checkNames ) { 
                XmlConvert.VerifyQName( name ); 
            }
            writer.WriteName( name ); 
        }

        public override void WriteQualifiedName( string localName, string ns ) {
            if ( checkNames ) { 
                ValidateNCName( localName );
            } 
            writer.WriteQualifiedName( localName, ns ); 
        }
 
//
//  Private methods
//
        private void CheckCharacters( string str ) { 
            XmlConvert.VerifyCharData( str, ExceptionType.ArgumentException );
        } 
 
        private void CheckCharacters( char[] data, int offset, int len ) {
            XmlConvert.VerifyCharData( data, offset, len, ExceptionType.ArgumentException ); 
        }

        private void ValidateNCName( string ncname ) {
            if ( ncname.Length == 0 ) { 
                throw new ArgumentException( Res.GetString( Res.Xml_EmptyName ) );
            } 
            int len = ValidateNames.ParseNCName( ncname, 0 ); 
            if ( len != ncname.Length ) {
                throw new ArgumentException( Res.GetString( len == 0 ? Res.Xml_BadStartNameChar : Res.Xml_BadNameChar, XmlException.BuildCharExceptionStr( ncname[len] ) ) ); 
            }
        }

        private void ValidateQName( string name ) { 
            if ( name.Length == 0 ) {
                throw new ArgumentException( Res.GetString( Res.Xml_EmptyName ) ); 
            } 
            int colonPos;
            int len = ValidateNames.ParseQName( name, 0, out colonPos ); 
            if ( len != name.Length ) {
                string res = ( len == 0 || ( colonPos > -1 && len == colonPos + 1 ) ) ? Res.Xml_BadStartNameChar : Res.Xml_BadNameChar;
                throw new ArgumentException( Res.GetString( res, XmlException.BuildCharExceptionStr( name[len] ) ) );
            } 
        }
 
        private string ReplaceNewLines( string str ) { 
            if ( str == null ) {
                return null; 
            }

            StringBuilder sb = null;
            int start = 0; 
            int i;
            for ( i = 0; i < str.Length; i++ ) { 
                char ch; 
                if ( ( ch = str[i] ) >= 0x20 ) {
                    continue; 
                }
                if ( ch == '\n' ) {
                    if ( newLineChars == "\n" ) {
                        continue; 
                    }
                    if ( sb == null ) { 
                        sb = new StringBuilder( str.Length + 5 ); 
                    }
                    sb.Append( str, start, i - start ); 
                }
                else if ( ch == '\r' ) {
                    if ( i + 1 < str.Length && str[i+1] == '\n' ) {
                        if ( newLineChars == "\r\n" ) { 
                            i++;
                            continue; 
                        } 
                        if ( sb == null ) {
                            sb = new StringBuilder( str.Length  + 5 ); 
                        }
                        sb.Append( str, start, i - start );
                        i++;
                    } 
                    else {
                        if ( newLineChars == "\r" ) { 
                            continue; 
                        }
                        if ( sb == null ) { 
                            sb = new StringBuilder( str.Length + 5 );
                        }
                        sb.Append( str, start, i - start );
                    } 
                }
                else { 
                    continue; 
                }
                sb.Append( newLineChars ); 
                start = i + 1;
            }

            if ( sb == null ) { 
                return str;
            } 
            else { 
                sb.Append( str, start, i - start );
                return sb.ToString(); 
            }
        }

        private string ReplaceNewLines( char[] data, int offset, int len ) { 
            if ( data == null ) {
                return null; 
            } 

            StringBuilder sb = null; 
            int start = offset;
            int endPos = offset + len;
            int i;
            for ( i = offset; i < endPos; i++ ) { 
                char ch;
                if ( ( ch = data[i] ) >= 0x20 ) { 
                    continue; 
                }
                if ( ch == '\n' ) { 
                    if ( newLineChars == "\n" ) {
                        continue;
                    }
                    if ( sb == null ) { 
                        sb = new StringBuilder( len + 5 );
                    } 
                    sb.Append( data, start, i - start ); 
                }
                else if ( ch == '\r' ) { 
                    if ( i + 1 < endPos && data[i+1] == '\n' ) {
                        if ( newLineChars == "\r\n" ) {
                            continue;
                        } 
                        if ( sb == null ) {
                            sb = new StringBuilder( len + 5 ); 
                        } 
                        sb.Append( data, start, i - start );
                        i++; 
                    }
                    else {
                        if ( newLineChars == "\r" ) {
                            continue; 
                        }
                        if ( sb == null ) { 
                            sb = new StringBuilder( len + 5 ); 
                        }
                        sb.Append( data, start, i - start ); 
                    }
                }
                else {
                    continue; 
                }
                sb.Append( newLineChars ); 
                start = i + 1; 
            }
 
            if ( sb == null ) {
                return null;
            }
            else { 
                sb.Append( data, start, i - start );
                return sb.ToString(); 
            } 
        }
 
        // interleave 2 adjacent invalid chars with a space, e.g. change "--" to "- -"
        private string InterleaveInvalidChars( string text, char invChar1, char invChar2 ) {
            StringBuilder sb = null;
            int start = 0; 
            int i;
            for ( i = 0; i < text.Length; i++ ) { 
                if ( text[i] != invChar2 ) { 
                    continue;
                } 
                if ( i > 0 && text[i-1] == invChar1 ) {
                    if ( sb == null ) {
                        sb = new StringBuilder( text.Length + 5 );
                    } 
                    sb.Append( text, start, i - start );
                    sb.Append( ' ' ); 
                    start = i; 
                }
            } 

            // check last char & return
            if ( sb == null ) {
                return ( i == 0 || text[i-1] != invChar1 ) ? text : ( text + ' ' ); 
            }
            else { 
                sb.Append( text, start, i - start ); 
                if ( i > 0 && text[i-1] == invChar1 ) {
                    sb.Append( ' ' ); 
                }
                return sb.ToString();
            }
        } 
    }
} 
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
using System; 
using System.IO;
using System.Text; 
using System.Xml.XPath;
using System.Xml.Schema;
using System.Collections;
using System.Diagnostics; 

namespace System.Xml { 
 
    //
    // XmlCharCheckingWriter 
    //
    internal class XmlCharCheckingWriter : XmlWrappingWriter {
//
// Fields 
//
        bool checkValues; 
        bool checkNames; 
        bool replaceNewLines;
        string newLineChars; 

        XmlCharType xmlCharType;
//
// Constructor 
//
        internal XmlCharCheckingWriter( XmlWriter baseWriter, bool checkValues, bool checkNames, bool replaceNewLines, string newLineChars ) 
            : base( baseWriter ) { 

            Debug.Assert( checkValues || replaceNewLines ); 
            this.checkValues = checkValues;
            this.checkNames = checkNames;
            this.replaceNewLines = replaceNewLines;
            this.newLineChars = newLineChars; 

            if ( checkValues ) { 
                xmlCharType = XmlCharType.Instance; 
            }
        } 

//
// XmlWriter implementation
// 

        public override XmlWriterSettings Settings { 
            get { 
                XmlWriterSettings s = base.writer.Settings;
                if ( s == null ) { 
                    s = new XmlWriterSettings();
                }
                else {
                    s = s.Clone(); 
                }
                if ( checkValues ) { 
                    s.CheckCharacters = true; 
                }
                if ( replaceNewLines ) { 
                    s.NewLineHandling = NewLineHandling.Replace;
                    s.NewLineChars = newLineChars;
                }
                s.ReadOnly = true; 
                return s;
            } 
        } 

        public override void WriteDocType( string name, string pubid, string sysid, string subset ) { 
            if ( checkNames ) {
                ValidateQName( name );
            }
            if ( checkValues ) { 
                if ( pubid != null ) {
                    int i; 
                    if ( ( i = xmlCharType.IsPublicId( pubid ) ) >= 0 ) { 
                        throw XmlConvert.CreateInvalidCharException( pubid[i] );
                    } 
                }
                if ( sysid != null ) {
                    CheckCharacters( sysid );
                } 
                if ( subset != null ) {
                    CheckCharacters( subset ); 
                } 
            }
            if ( replaceNewLines ) { 
                sysid = ReplaceNewLines( sysid );
                pubid = ReplaceNewLines( pubid );
                subset = ReplaceNewLines( subset );
            } 
            writer.WriteDocType( name, pubid, sysid, subset );
        } 
 
        public override void WriteStartElement( string prefix, string localName, string ns ) {
            if ( checkNames ) { 
                if ( localName == null || localName.Length == 0 ) {
                    throw new ArgumentException( Res.GetString( Res.Xml_EmptyLocalName ) );
                }
                ValidateNCName( localName ); 

                if ( prefix != null && prefix.Length > 0 ) { 
                    ValidateNCName( prefix ); 
                }
            } 
            writer.WriteStartElement( prefix, localName, ns );
        }

        public override void WriteStartAttribute( string prefix, string localName, string ns ) { 
            if ( checkNames ) {
                if ( localName == null || localName.Length == 0 ) { 
                    throw new ArgumentException( Res.GetString( Res.Xml_EmptyLocalName ) ); 
                }
                ValidateNCName( localName ); 

                if ( prefix != null && prefix.Length > 0 ) {
                    ValidateNCName( prefix );
                } 
            }
            writer.WriteStartAttribute( prefix, localName, ns ); 
        } 

        public override void WriteCData( string text ) { 
            if ( text != null ) {
                if ( checkValues ) {
                    CheckCharacters( text );
                } 
                if ( replaceNewLines ) {
                    text = ReplaceNewLines( text ); 
                } 
                int i;
                while ( ( i = text.IndexOf( "]]>", StringComparison.Ordinal ) ) >= 0 ) { 
                    writer.WriteCData( text.Substring( 0, i + 2 ) );
                    text = text.Substring( i + 2 );
                }
            } 
            writer.WriteCData( text );
        } 
 
        public override void WriteComment( string text ) {
            if ( text != null ) { 
                if ( checkValues ) {
                    CheckCharacters( text );
                    text = InterleaveInvalidChars( text, '-', '-' );
                } 
                if ( replaceNewLines ) {
                    text = ReplaceNewLines( text ); 
                } 
            }
            writer.WriteComment( text ); 
        }

        public override void WriteProcessingInstruction( string name, string text ) {
            if ( checkNames ) { 
                ValidateNCName( name );
            } 
            if ( text != null ) { 
                if ( checkValues ) {
                    CheckCharacters( text ); 
                    text = InterleaveInvalidChars( text, '?', '>' );
                }
                if ( replaceNewLines ) {
                    text = ReplaceNewLines( text ); 
                }
            } 
            writer.WriteProcessingInstruction( name, text ); 
        }
 
        public override void WriteEntityRef( string name ) {
            if ( checkNames ) {
                ValidateQName( name );
            } 
            writer.WriteEntityRef( name );
        } 
 
        public override void WriteWhitespace( string ws ) {
            // "checkNames" is intentional here; if false, the whitespaces are checked in XmlWellformedWriter 
            if ( checkNames ) {
                int i;
                if ( ( i = xmlCharType.IsOnlyWhitespaceWithPos( ws ) ) != -1 ) {
                    throw new ArgumentException( Res.GetString( Res.Xml_InvalidWhitespaceCharacter, XmlException.BuildCharExceptionStr( ws[i] ) ) ); 
                }
            } 
            writer.WriteWhitespace( ws ); 
        }
 
        public override void WriteString( string text ) {
            if ( text != null ) {
                if ( checkValues ) {
                    CheckCharacters( text ); 
                }
                if ( replaceNewLines && WriteState != WriteState.Attribute ) { 
                    text = ReplaceNewLines( text ); 
                }
            } 
            writer.WriteString( text );
        }

        public override void WriteSurrogateCharEntity( char lowChar, char highChar ) { 
            writer.WriteSurrogateCharEntity( lowChar, highChar );
        } 
 
        public override void WriteChars( char[] buffer, int index, int count ) {
            if ( checkValues ) { 
                CheckCharacters( buffer, index, count );
            }
            if ( replaceNewLines && WriteState != WriteState.Attribute ) {
                string text = ReplaceNewLines( buffer, index, count ); 
                if ( text != null ) {
                    WriteString( text ); 
                    return; 
                }
            } 
            writer.WriteChars( buffer, index, count );
        }

        public override void WriteNmToken( string name ) { 
            if ( checkNames ) {
                if ( name == null || name.Length == 0 ) { 
                    throw new ArgumentException( Res.GetString( Res.Xml_EmptyName ) ); 
                }
                XmlConvert.VerifyNMTOKEN( name ); 
            }
            writer.WriteNmToken( name );
        }
 
        public override void WriteName( string name ) {
            if ( checkNames ) { 
                XmlConvert.VerifyQName( name ); 
            }
            writer.WriteName( name ); 
        }

        public override void WriteQualifiedName( string localName, string ns ) {
            if ( checkNames ) { 
                ValidateNCName( localName );
            } 
            writer.WriteQualifiedName( localName, ns ); 
        }
 
//
//  Private methods
//
        private void CheckCharacters( string str ) { 
            XmlConvert.VerifyCharData( str, ExceptionType.ArgumentException );
        } 
 
        private void CheckCharacters( char[] data, int offset, int len ) {
            XmlConvert.VerifyCharData( data, offset, len, ExceptionType.ArgumentException ); 
        }

        private void ValidateNCName( string ncname ) {
            if ( ncname.Length == 0 ) { 
                throw new ArgumentException( Res.GetString( Res.Xml_EmptyName ) );
            } 
            int len = ValidateNames.ParseNCName( ncname, 0 ); 
            if ( len != ncname.Length ) {
                throw new ArgumentException( Res.GetString( len == 0 ? Res.Xml_BadStartNameChar : Res.Xml_BadNameChar, XmlException.BuildCharExceptionStr( ncname[len] ) ) ); 
            }
        }

        private void ValidateQName( string name ) { 
            if ( name.Length == 0 ) {
                throw new ArgumentException( Res.GetString( Res.Xml_EmptyName ) ); 
            } 
            int colonPos;
            int len = ValidateNames.ParseQName( name, 0, out colonPos ); 
            if ( len != name.Length ) {
                string res = ( len == 0 || ( colonPos > -1 && len == colonPos + 1 ) ) ? Res.Xml_BadStartNameChar : Res.Xml_BadNameChar;
                throw new ArgumentException( Res.GetString( res, XmlException.BuildCharExceptionStr( name[len] ) ) );
            } 
        }
 
        private string ReplaceNewLines( string str ) { 
            if ( str == null ) {
                return null; 
            }

            StringBuilder sb = null;
            int start = 0; 
            int i;
            for ( i = 0; i < str.Length; i++ ) { 
                char ch; 
                if ( ( ch = str[i] ) >= 0x20 ) {
                    continue; 
                }
                if ( ch == '\n' ) {
                    if ( newLineChars == "\n" ) {
                        continue; 
                    }
                    if ( sb == null ) { 
                        sb = new StringBuilder( str.Length + 5 ); 
                    }
                    sb.Append( str, start, i - start ); 
                }
                else if ( ch == '\r' ) {
                    if ( i + 1 < str.Length && str[i+1] == '\n' ) {
                        if ( newLineChars == "\r\n" ) { 
                            i++;
                            continue; 
                        } 
                        if ( sb == null ) {
                            sb = new StringBuilder( str.Length  + 5 ); 
                        }
                        sb.Append( str, start, i - start );
                        i++;
                    } 
                    else {
                        if ( newLineChars == "\r" ) { 
                            continue; 
                        }
                        if ( sb == null ) { 
                            sb = new StringBuilder( str.Length + 5 );
                        }
                        sb.Append( str, start, i - start );
                    } 
                }
                else { 
                    continue; 
                }
                sb.Append( newLineChars ); 
                start = i + 1;
            }

            if ( sb == null ) { 
                return str;
            } 
            else { 
                sb.Append( str, start, i - start );
                return sb.ToString(); 
            }
        }

        private string ReplaceNewLines( char[] data, int offset, int len ) { 
            if ( data == null ) {
                return null; 
            } 

            StringBuilder sb = null; 
            int start = offset;
            int endPos = offset + len;
            int i;
            for ( i = offset; i < endPos; i++ ) { 
                char ch;
                if ( ( ch = data[i] ) >= 0x20 ) { 
                    continue; 
                }
                if ( ch == '\n' ) { 
                    if ( newLineChars == "\n" ) {
                        continue;
                    }
                    if ( sb == null ) { 
                        sb = new StringBuilder( len + 5 );
                    } 
                    sb.Append( data, start, i - start ); 
                }
                else if ( ch == '\r' ) { 
                    if ( i + 1 < endPos && data[i+1] == '\n' ) {
                        if ( newLineChars == "\r\n" ) {
                            continue;
                        } 
                        if ( sb == null ) {
                            sb = new StringBuilder( len + 5 ); 
                        } 
                        sb.Append( data, start, i - start );
                        i++; 
                    }
                    else {
                        if ( newLineChars == "\r" ) {
                            continue; 
                        }
                        if ( sb == null ) { 
                            sb = new StringBuilder( len + 5 ); 
                        }
                        sb.Append( data, start, i - start ); 
                    }
                }
                else {
                    continue; 
                }
                sb.Append( newLineChars ); 
                start = i + 1; 
            }
 
            if ( sb == null ) {
                return null;
            }
            else { 
                sb.Append( data, start, i - start );
                return sb.ToString(); 
            } 
        }
 
        // interleave 2 adjacent invalid chars with a space, e.g. change "--" to "- -"
        private string InterleaveInvalidChars( string text, char invChar1, char invChar2 ) {
            StringBuilder sb = null;
            int start = 0; 
            int i;
            for ( i = 0; i < text.Length; i++ ) { 
                if ( text[i] != invChar2 ) { 
                    continue;
                } 
                if ( i > 0 && text[i-1] == invChar1 ) {
                    if ( sb == null ) {
                        sb = new StringBuilder( text.Length + 5 );
                    } 
                    sb.Append( text, start, i - start );
                    sb.Append( ' ' ); 
                    start = i; 
                }
            } 

            // check last char & return
            if ( sb == null ) {
                return ( i == 0 || text[i-1] != invChar1 ) ? text : ( text + ' ' ); 
            }
            else { 
                sb.Append( text, start, i - start ); 
                if ( i > 0 && text[i-1] == invChar1 ) {
                    sb.Append( ' ' ); 
                }
                return sb.ToString();
            }
        } 
    }
} 
 

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

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