TextDecorationCollectionConverter.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / System / Windows / TextDecorationCollectionConverter.cs / 1 / TextDecorationCollectionConverter.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: TextDecorationCollectionConverter class 
//
// History: 
//  2/23/2004: [....] Created the file
//
//---------------------------------------------------------------------------
using System; 
using System.Collections;
using System.Collections.Generic; 
using System.ComponentModel; 
using System.ComponentModel.Design.Serialization;
using System.Globalization; 
using System.Reflection;
using System.Security;

using SR=MS.Internal.PresentationCore.SR; 
using SRID=MS.Internal.PresentationCore.SRID;
 
namespace System.Windows 
{
    ///  
    /// TypeConverter for TextDecorationCollection
    /// 
    public sealed class TextDecorationCollectionConverter : TypeConverter
    { 
        /// 
        /// CanConvertTo method 
        ///  
        ///  ITypeDescriptorContext 
        ///  Type to convert to  
        ///  false will always be returned because TextDecorations cannot be converted to any other type. 
        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            if (destinationType == typeof(InstanceDescriptor)) 
            {
                return true; 
            } 

            // return false for any other target type. Don't call base.CanConvertTo() because it would be confusing 
            // in some cases. For example, for destination typeof(String), base convertor just converts the TDC to the
            // string full name of the type.
            return false;
        } 

        ///  
        /// CanConvertFrom 
        /// 
        ///  ITypeDescriptorContext  
        /// Type to convert to 
        ///  true if it can convert from sourceType to TextDecorations, false otherwise 
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        { 
            if (sourceType == typeof(string))
            { 
                return true; 
            }
 
            return false;
        }

        ///  
        /// ConvertFrom
        ///  
        ///  ITypeDescriptorContext  
        ///  CultureInfo 
        ///  The input object to be converted to TextDecorations  
        ///  the converted value of the input object 
        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object input)
        {
            if (input == null) 
            {
                throw GetConvertFromException(input); 
            } 

            string value = input as string; 

            if (null == value)
            {
                throw new ArgumentException(SR.Get(SRID.General_BadType, "ConvertFrom"), "input"); 
            }
 
            return ConvertFromString(value); 
        }
 
        /// 
        /// ConvertFromString
        /// 
        ///  The string to be converted into TextDecorationCollection object  
        ///  the converted value of the string flag 
        ///  
        /// The text parameter can be either string "None" or a combination of the predefined 
        /// TextDecoration names delimited by commas (,). One or more blanks spaces can precede
        /// or follow each text decoration name or comma. There can't be duplicate TextDecoration names in the 
        /// string. The operation is case-insensitive.
        /// 
        public static new TextDecorationCollection ConvertFromString(string text)
        { 
            if (text == null)
            { 
               return null; 
            }
 
            TextDecorationCollection textDecorations = new TextDecorationCollection();

            // Flags indicating which Predefined textDecoration has alrady been added.
            byte MatchedTextDecorationFlags = 0; 

            // Start from the 1st non-whitespace character 
            // Negative index means error is encountered 
            int index = AdvanceToNextNonWhiteSpace(text, 0);
            while (index >= 0 && index < text.Length) 
            {
                if (Match(None, text, index))
                {
                    // Matched "None" in the input 
                    index = AdvanceToNextNonWhiteSpace(text, index + None.Length);
                    if (textDecorations.Count > 0 || index < text.Length) 
                    { 
                        // Error: "None" can only be specified by its own
                        index = -1; 
                    }
                }
                else
                { 
                    // Match the input with one of the predefined text decoration names
                    int i; 
                    for(i = 0; 
                           i < TextDecorationNames.Length
                        && !Match(TextDecorationNames[i], text, index); 
                       i++
                    );

                    if (i < TextDecorationNames.Length) 
                    {
                        // Found a match within the predefined names 
                        if ((MatchedTextDecorationFlags & (1 << i)) > 0) 
                        {
                            // Error: The matched value is duplicated. 
                            index = -1;
                        }
                        else
                        { 
                            // Valid match. Add to the collection and remember that this text decoration
                            // has been added 
                            textDecorations.Add(PredefinedTextDecorations[i]); 
                            MatchedTextDecorationFlags |= (byte)(1 << i);
 
                            // Advance to the start of next name
                            index = AdvanceToNextNameStart(text, index + TextDecorationNames[i].Length);
                        }
                    } 
                    else
                    { 
                        // Error: no match found in the predefined names 
                        index = -1;
                    } 
                }
            }

            if (index < 0) 
            {
                throw new ArgumentException(SR.Get(SRID.InvalidTextDecorationCollectionString, text)); 
            } 

            return textDecorations; 
        }

        /// 
        /// ConvertTo 
        /// 
        ///  ITypeDescriptorContext  
        ///  CultureInfo  
        ///  the object to be converted to another type 
        ///  The destination type of the conversion  
        ///  null will always be returned because TextDecorations cannot be converted to any other type. 
        ///
        ///     Critical: calls InstanceDescriptor ctor which LinkDemands
        ///     PublicOK: can only make an InstanceDescriptor for TextDecoration, not an arbitrary class 
        ///
        [SecurityCritical] 
        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType) 
        {
            if (destinationType == typeof(InstanceDescriptor) && value is IEnumerable) 
            {
                ConstructorInfo ci = typeof(TextDecorationCollection).GetConstructor(
                    new Type[]{typeof(IEnumerable)}
                    ); 

                return new InstanceDescriptor(ci, new object[]{value}); 
            } 

            // Pass unhandled cases to base class (which will throw exceptions for null value or destinationType.) 
            return base.ConvertTo(context, culture, value, destinationType);
        }

        //--------------------------------- 
        // Private methods
        //--------------------------------- 
        ///  
        /// Match the input against a predefined pattern from certain index onwards
        ///  
        private static bool Match(string pattern, string input, int index)
        {
            int i = 0;
            for (; 
                    i < pattern.Length
                 && index + i < input.Length 
                 && pattern[i] == Char.ToUpperInvariant(input[index + i]); 
                 i++) ;
 
            return (i == pattern.Length);
        }

        ///  
        /// Advance to the start of next name
        ///  
        private static int AdvanceToNextNameStart(string input, int index) 
        {
            // Two names must be seperated by a comma and optionally spaces 
            int separator = AdvanceToNextNonWhiteSpace(input, index);

            int nextNameStart;
            if (separator >= input.Length) 
            {
                // reach the end 
                nextNameStart = input.Length; 
            }
            else 
            {
                if (input[separator] == Separator)
                {
                    nextNameStart = AdvanceToNextNonWhiteSpace(input, separator + 1); 
                    if (nextNameStart >= input.Length)
                    { 
                        // Error: Separator is at the end of the input 
                        nextNameStart = -1;
                    } 
                }
                else
                {
                    // Error: There is a non-whitespace, non-separator character following 
                    // the matched value
                    nextNameStart = -1; 
                } 
            }
 
            return nextNameStart;
        }

        ///  
        /// Advance to the next non-whitespace character
        ///  
        private static int AdvanceToNextNonWhiteSpace(string input, int index) 
        {
            for (; index < input.Length && Char.IsWhiteSpace(input[index]); index++) ; 
            return (index > input.Length) ? input.Length : index;
        }

        //--------------------------------- 
        // Private members
        //--------------------------------- 
 
        //
        // Predefined valid names for TextDecorations 
        // Names should be normalized to be upper case
        //
        private const string None    = "NONE";
        private const char Separator = ','; 

        private static readonly string[] TextDecorationNames = new string[] { 
            "OVERLINE", 
            "BASELINE",
            "UNDERLINE", 
            "STRIKETHROUGH"
            };

        // Predefined TextDecorationCollection values. It should match 
        // the TextDecorationNames array
        private static readonly TextDecorationCollection[] PredefinedTextDecorations = 
            new TextDecorationCollection[] { 
                TextDecorations.OverLine,
                TextDecorations.Baseline, 
                TextDecorations.Underline,
                TextDecorations.Strikethrough
                };
 
    }
} 

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