ModifierKeysConverter.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Base / System / Windows / Input / ModifierKeysConverter.cs / 1305600 / ModifierKeysConverter.cs
                        
                        
                             	//---------------------------------------------------------------------------- 
//
// File: ModifierKeysConverter.cs
//
// Description: 
//
//      ModifierKeysConverter : Converts a Modifier string to the *Type* that the string represents and vice-versa. 
// 
// Features:
// 
// History:
//  05/28/2003       created: Chandrasekhar Rentachintala
//
// Copyright (C) 2003 by Microsoft Corporation.  All rights reserved. 
//
//--------------------------------------------------------------------------- 
using System; 
using System.ComponentModel;    // for TypeConverter
using System.Globalization;     // for CultureInfo 
using System.Reflection;
using MS.Internal;
using System.Windows;
using System.Windows.Input; 
using System.Windows.Markup;
using MS.Utility; 
using MS.Internal.WindowsBase; 

namespace System.Windows.Input 
{
    /// 
    /// Key Converter class for converting between a string and the Type of a Modifiers
    ///  
    /// 
    public class ModifierKeysConverter : TypeConverter 
    { 
        /// 
        /// CanConvertFrom() 
        /// 
        /// 
        /// 
        ///  
        /// 
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType) 
        { 
            // We can only handle string.
            if (sourceType == typeof(string)) 
            {
                return true;
            }
            else 
            {
                return false; 
            } 
        }
 
        /// 
        /// TypeConverter method override.
        /// 
        /// ITypeDescriptorContext 
        /// Type to convert to
        /// true if conversion is possible 
        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType) 
        {
            // We can convert to a string. 
            if (destinationType == typeof(string))
            {
                // When invoked by the serialization engine we can convert to string only for known type
                if (context != null && context.Instance != null && 
					context.Instance is ModifierKeys)
                { 
                    return (IsDefinedModifierKeys((ModifierKeys)context.Instance)); 
                }
            } 
            return false;
        }

        ///  
        /// ConvertFrom()
        ///  
        ///  
        /// 
        ///  
        /// 
        /// 
        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object source)
        { 
            if (source is string)
            { 
                string modifiersToken = ((string)source).Trim(); 
                ModifierKeys modifiers = GetModifierKeys(modifiersToken, CultureInfo.InvariantCulture);
                return modifiers; 
            }
            throw GetConvertFromException(source);
        }
 
        /// 
        /// ConvertTo() 
        ///  
        /// 
        ///  
        /// 
        /// 
        /// 
        ///  
        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        { 
            if (destinationType == null) 
                throw new ArgumentNullException("destinationType");
 
            if (destinationType == typeof(string))
            {
                ModifierKeys modifiers = (ModifierKeys)value;
 
                if (!IsDefinedModifierKeys(modifiers))
                    throw new InvalidEnumArgumentException("value", (int)modifiers, typeof(ModifierKeys)); 
                else 
                {
                    string strModifiers = ""; 

                    if ((modifiers & ModifierKeys.Control) == ModifierKeys.Control)
                    {
                        strModifiers += MatchModifiers(ModifierKeys.Control); 
                    }
 
                    if ((modifiers & ModifierKeys.Alt) == ModifierKeys.Alt) 
                    {
                        if (strModifiers.Length > 0) 
                            strModifiers += Modifier_Delimiter;

                        strModifiers += MatchModifiers(ModifierKeys.Alt);
                    } 

                    if ((modifiers & ModifierKeys.Windows) == ModifierKeys.Windows) 
                    { 
                        if (strModifiers.Length > 0)
                            strModifiers += Modifier_Delimiter; 

                        strModifiers += MatchModifiers(ModifierKeys.Windows); ;
                    }
 
                    if ((modifiers & ModifierKeys.Shift) == ModifierKeys.Shift)
                    { 
                        if (strModifiers.Length > 0) 
                            strModifiers += Modifier_Delimiter;
 
                        strModifiers += MatchModifiers(ModifierKeys.Shift); ;
                    }

                    return strModifiers; 
                }
            } 
            throw GetConvertToException(value,destinationType); 
        }
 
        private ModifierKeys GetModifierKeys(string modifiersToken, CultureInfo culture)
        {
            ModifierKeys modifiers = ModifierKeys.None;
            if (modifiersToken.Length != 0) 
            {
                int offset = 0; 
                do 
                {
                    offset = modifiersToken.IndexOf(Modifier_Delimiter); 
                    string token = (offset < 0) ? modifiersToken : modifiersToken.Substring(0, offset);
                    token = token.Trim();
                    token = token.ToUpper(culture);
 
                    if (token == String.Empty)
                        break; 
 
                    switch (token)
                    { 
                        case "CONTROL" :
                        case "CTRL" :
                            modifiers |= ModifierKeys.Control;
                            break; 

                        case "SHIFT" : 
                            modifiers |= ModifierKeys.Shift; 
                            break;
 
                        case "ALT":
                            modifiers |= ModifierKeys.Alt;
                            break;
 
                        case "WINDOWS":
                        case "WIN": 
                            modifiers |= ModifierKeys.Windows; 
                            break;
 
                        default:
                            throw new NotSupportedException(SR.Get(SRID.Unsupported_Modifier, token));
                    }
 
                    modifiersToken = modifiersToken.Substring(offset + 1);
                } while (offset != -1); 
            } 
            return modifiers;
        } 

        /// 
        ///     Check for Valid enum, as any int can be casted to the enum.
        ///  
        public static bool IsDefinedModifierKeys(ModifierKeys modifierKeys)
        { 
            return (modifierKeys == ModifierKeys.None || (((int)modifierKeys & ~((int)ModifierKeysFlag)) == 0)); 
        }
 
	    private const char Modifier_Delimiter = '+';

        private static ModifierKeys ModifierKeysFlag  =  ModifierKeys.Windows | ModifierKeys.Shift |
                                                         ModifierKeys.Alt     | ModifierKeys.Control ; 

        internal static string MatchModifiers(ModifierKeys modifierKeys) 
        { 
            string modifiers = String.Empty;
            switch (modifierKeys) 
            {
                case ModifierKeys.Control: modifiers="Ctrl";break;
                case ModifierKeys.Shift  : modifiers="Shift";break;
                case ModifierKeys.Alt    : modifiers="Alt";break; 
                case ModifierKeys.Windows: modifiers="Windows";break;
            } 
            return modifiers; 
        }
    } 
}

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