TypeConverterBase.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / NetFx40 / System.Activities / System / Activities / XamlIntegration / TypeConverterBase.cs / 1305376 / TypeConverterBase.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------------------------

namespace System.Activities.XamlIntegration 
{
    using System; 
    using System.Collections.Concurrent; 
    using System.ComponentModel;
    using System.Globalization; 
    using System.Runtime;
    using System.Threading;
    using System.Xaml;
 
    public abstract class TypeConverterBase : TypeConverter
    { 
        Lazy> helpers = new Lazy>(); 
        TypeConverterHelper helper;
        Type baseType; 
        Type helperType;

        internal TypeConverterBase(Type baseType, Type helperType)
        { 
            this.baseType = baseType;
            this.helperType = helperType; 
        } 

        internal TypeConverterBase(Type targetType, Type baseType, Type helperType) 
        {
            this.helper = GetTypeConverterHelper(targetType, baseType, helperType);
        }
 
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        { 
            if (sourceType == TypeHelper.StringType) 
            {
                return true; 
            }

            return base.CanConvertFrom(context, sourceType);
        } 

        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType) 
        { 
            if (destinationType == TypeHelper.StringType)
            { 
                return false;
            }
            return base.CanConvertTo(context, destinationType);
        } 

        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value) 
        { 
            string stringValue = value as string;
            if (stringValue != null) 
            {
                TypeConverterHelper currentHelper = helper;
                if (currentHelper == null)
                { 
                    IDestinationTypeProvider targetService = context.GetService(typeof(IDestinationTypeProvider)) as IDestinationTypeProvider;
                    Type targetType = targetService.GetDestinationType(); 
 
                    if (!this.helpers.Value.TryGetValue(targetType, out currentHelper))
                    { 
                        currentHelper = GetTypeConverterHelper(targetType, this.baseType, this.helperType);
                        if (!this.helpers.Value.TryAdd(targetType, currentHelper))
                        {
                            if (!this.helpers.Value.TryGetValue(targetType, out currentHelper)) 
                            {
                                throw FxTrace.Exception.AsError(new InvalidOperationException(SR.TypeConverterHelperCacheAddFailed(targetType))); 
                            } 
                        }
                    } 
                }
                object result = currentHelper.UntypedConvertFromString(stringValue, context);
                return result;
            } 

            return base.ConvertFrom(context, culture, value); 
        } 

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType) 
        {
            return base.ConvertTo(context, culture, value, destinationType);
        }
 
        TypeConverterHelper GetTypeConverterHelper(Type targetType, Type baseType, Type helperType)
        { 
            Type[] genericTypeArguments; 
            if (baseType.BaseType == targetType)
            { 
                // support non-generic ActivityWithResult, In/Out/InOutArgument
                genericTypeArguments = new Type[] { TypeHelper.ObjectType };
            }
            else 
            {
                // Find baseType in the base class list of targetType 
                while (!targetType.IsGenericType || 
                    !(targetType.GetGenericTypeDefinition() == baseType))
                { 
                    if (targetType == TypeHelper.ObjectType)
                    {
                        throw FxTrace.Exception.AsError(new InvalidOperationException(SR.InvalidTypeConverterUsage));
                    } 

                    targetType = targetType.BaseType; 
                } 
                genericTypeArguments = targetType.GetGenericArguments();
            } 

            Type concreteHelperType = helperType.MakeGenericType(genericTypeArguments);
            return (TypeConverterHelper)Activator.CreateInstance(concreteHelperType);
        } 

        internal abstract class TypeConverterHelper 
        { 
            public abstract object UntypedConvertFromString(string text, ITypeDescriptorContext context);
 
            public static T GetService(ITypeDescriptorContext context) where T : class
            {
                T service = (T)context.GetService(typeof(T));
                if (service == null) 
                {
                    throw FxTrace.Exception.AsError(new InvalidOperationException(SR.InvalidTypeConverterUsage)); 
                } 

                return service; 
            }
        }

        internal abstract class TypeConverterHelper : TypeConverterHelper 
        {
            public abstract T ConvertFromString(string text, ITypeDescriptorContext context); 
 
            public sealed override object UntypedConvertFromString(string text, ITypeDescriptorContext context)
            { 
                return ConvertFromString(text, context);
            }
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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TypeConverterBase.cs source code in C# .NET

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