OleAutBinder.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / OleAutBinder.cs / 1 / OleAutBinder.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// This class represents the Ole Automation binder.
 
// #define DISPLAY_DEBUG_INFO 

namespace System { 

    using System;
    using System.Runtime.InteropServices;
    using System.Reflection; 
    using Microsoft.Win32;
    using CultureInfo = System.Globalization.CultureInfo; 
 
    // Made serializable in anticipation of this class eventually having state.
    [Serializable()] 
    internal class OleAutBinder : DefaultBinder
    {
        // ChangeType
        // This binder uses OLEAUT to change the type of the variant. 
        public override Object ChangeType(Object value, Type type, CultureInfo cultureInfo)
        { 
            Variant myValue = new Variant(value); 
            if (cultureInfo == null)
                cultureInfo = CultureInfo.CurrentCulture; 

    #if DISPLAY_DEBUG_INFO
            Console.Write("In OleAutBinder::ChangeType converting variant of type: ");
            Console.Write(myValue.VariantType); 
            Console.Write(" to type: ");
            Console.WriteLine(type.Name); 
    #endif 

            if (type.IsByRef) 
            {
    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Striping byref from the type to convert to.");
    #endif 
                type = type.GetElementType();
            } 
 
            // If we are trying to convert from an object to another type then we don't
            // need the OLEAUT change type, we can just use the normal COM+ mechanisms. 
            if (!type.IsPrimitive && type.IsInstanceOfType(value))
            {
    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Source variant can be assigned to destination type"); 
    #endif
                return value; 
            } 

            Type srcType = value.GetType(); 

            // Handle converting primitives to enums.
            if (type.IsEnum && srcType.IsPrimitive)
            { 
    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Converting primitive to enum"); 
    #endif 
                return Enum.Parse(type, value.ToString());
            } 

            // Special case the convertion from DBNull.
            if (srcType == typeof(DBNull))
            { 
                // The requested type is a DBNull so no convertion is required.
                if (type == typeof(DBNull)) 
                    return value; 

                // Visual J++ supported converting from DBNull to null so customers 
                // have requested (via a CDCR) that DBNull be convertible to null.
                // We don't however allow this when converting to a value class, since null
                // doesn't make sense for these, or to object since this would change existing
                // semantics. 
                if ((type.IsClass && type != typeof(Object)) || type.IsInterface)
                    return null; 
            } 

#if FEATURE_COMINTEROP 
            // Use the OA variant lib to convert primitive types.
            try
            {
    #if DISPLAY_DEBUG_INFO 
                Console.WriteLine("Using OAVariantLib.ChangeType() to do the conversion");
    #endif 
                // Specify the LocalBool flag to have BOOL values converted to local language rather 
                // than 0 or -1.
                Object RetObj = OAVariantLib.ChangeType(myValue, type, OAVariantLib.LocalBool, cultureInfo).ToObject(); 

    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Object returned from ChangeType is of type: " + RetObj.GetType().Name);
    #endif 

                return RetObj; 
            } 
    #if DISPLAY_DEBUG_INFO
            catch(NotSupportedException e) 
    #else
            catch(NotSupportedException)
    #endif
            { 
    #if DISPLAY_DEBUG_INFO
                Console.Write("Exception thrown: "); 
                Console.WriteLine(e); 
    #endif
                throw new COMException(Environment.GetResourceString("Interop.COM_TypeMismatch"), unchecked((int)0x80020005)); 
            }

#else // !FEATURE_COMINTEROP
 
            return base.ChangeType(value, type, cultureInfo);
 
#endif // !FEATURE_COMINTEROP 
        }
 

#if !FEATURE_COMINTEROP
        // CanChangeType
        public override bool CanChangeType(Object value, Type type, CultureInfo cultureInfo) 
        {
            Variant myValue = new Variant(value); 
            if (cultureInfo == null) 
                cultureInfo = CultureInfo.CurrentCulture;
 
    #if DISPLAY_DEBUG_INFO
            Console.Write("In OleAutBinder::CanChangeType converting variant of type: ");
            Console.Write(myValue.VariantType);
            Console.Write(" to type: "); 
            Console.WriteLine(type.Name);
    #endif 
 
            // If we are trying to convert to variant then there is nothing to do.
            if (type == typeof(Variant)) 
            {
    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Variant being changed to type variant is always legal");
    #endif 
                return true;
            } 
 
            if (type.IsByRef)
            { 
    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Striping byref from the type to convert to.");
    #endif
                type = type.GetElementType(); 
            }
 
            // If we are trying to convert from an object to another type then we don't 
            // need the OLEAUT change type, we can just use the normal COM+ mechanisms.
            if (!type.IsPrimitive && type.IsInstanceOfType(value)) 
            {
    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Source variant can be assigned to destination type");
    #endif 
                return true;
            } 
 
            // Handle converting primitives to enums.
            if (type.IsEnum && value.GetType().IsPrimitive) 
            {
    #if DISPLAY_DEBUG_INFO
                Console.WriteLine("Converting primitive to enum");
    #endif 
                return true;
            } 
 
            return base.CanChangeType(value, type, cultureInfo);
        } 
#endif // FEATURE_COMINTEROP
    }
}

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