UnmanagedMarshal
Class
Definition
Represents the class that describes how to marshal a field from managed to unmanaged code. This class cannot be inherited.
[System.Obsolete("An alternate API is available: Emit the MarshalAs custom attribute instead.")]
[System.Runtime.InteropServices.ComVisible(true)]
public sealed class UnmanagedMarshal
- Inheritance
-
UnmanagedMarshal
- Attributes
Inherited Members
System.Object
Examples
The following code example shows replacement code for the obsolete UnmanagedMarshal type. The example emits a single-module assembly named EmitMarshalAs.dll, containing a type named Sample. The type has a method named Test, with one parameter of type String. The code example applies the MarshalAsAttribute with UnmanagedType to the parameter.
You can use the Ildasm.exe (IL Disassembler) to examine the emitted assembly and observe that the parameter is marked marshal(bstr).
using namespace System;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
using namespace System::Runtime::InteropServices;
void main()
{
AppDomain^ myDomain = AppDomain::CurrentDomain;
AssemblyName^ myAsmName = gcnew AssemblyName("EmitMarshalAs");
AssemblyBuilder^ myAssembly =
myDomain->DefineDynamicAssembly(myAsmName,
AssemblyBuilderAccess::RunAndSave);
ModuleBuilder^ myModule =
myAssembly->DefineDynamicModule(myAsmName->Name,
myAsmName->Name + ".dll");
TypeBuilder^ myType =
myModule->DefineType("Sample", TypeAttributes::Public);
MethodBuilder^ myMethod =
myType->DefineMethod("Test", MethodAttributes::Public,
nullptr, gcnew array<Type^> { String::typeid });
// Get a parameter builder for the parameter that needs the
// attribute, using the HasFieldMarshal attribute. In this
// example, the parameter is at position 0 and has the name
// "arg".
ParameterBuilder^ pb =
myMethod->DefineParameter(0,
ParameterAttributes::HasFieldMarshal, "arg");
// Get the MarshalAsAttribute constructor that takes an
// argument of type UnmanagedType.
//
//Type^ maattrType = MarshalAsAttribute::typeid;
ConstructorInfo^ ci =
(MarshalAsAttribute::typeid)->GetConstructor(
gcnew array<Type^> { UnmanagedType::typeid });
// Create a CustomAttributeBuilder representing the attribute,
// specifying the necessary unmanaged type. In this case,
// UnmanagedType.BStr is specified.
//
CustomAttributeBuilder^ cabuilder =
gcnew CustomAttributeBuilder(
ci, gcnew array<Object^> { UnmanagedType::BStr });
// Apply the attribute to the parameter.
//
pb->SetCustomAttribute(cabuilder);
ILGenerator^ il = myMethod->GetILGenerator();
il->Emit(OpCodes::Ret);
Type^ finished = myType->CreateType();
myAssembly->Save(myAsmName->Name + ".dll");
}
using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.InteropServices;
public class Example
{
public static void Main()
{
AppDomain myDomain = AppDomain.CurrentDomain;
AssemblyName myAsmName = new AssemblyName("EmitMarshalAs");
AssemblyBuilder myAssembly =
myDomain.DefineDynamicAssembly(myAsmName,
AssemblyBuilderAccess.RunAndSave);
ModuleBuilder myModule =
myAssembly.DefineDynamicModule(myAsmName.Name,
myAsmName.Name + ".dll");
TypeBuilder myType =
myModule.DefineType("Sample", TypeAttributes.Public);
MethodBuilder myMethod =
myType.DefineMethod("Test", MethodAttributes.Public,
null, new Type[] { typeof(string) });
// Get a parameter builder for the parameter that needs the
// attribute, using the HasFieldMarshal attribute. In this
// example, the parameter is at position 0 and has the name
// "arg".
ParameterBuilder pb =
myMethod.DefineParameter(0,
ParameterAttributes.HasFieldMarshal, "arg");
// Get the MarshalAsAttribute constructor that takes an
// argument of type UnmanagedType.
//
ConstructorInfo ci =
typeof(MarshalAsAttribute).GetConstructor(
new Type[] { typeof(UnmanagedType) });
// Create a CustomAttributeBuilder representing the attribute,
// specifying the necessary unmanaged type. In this case,
// UnmanagedType.BStr is specified.
//
CustomAttributeBuilder cabuilder =
new CustomAttributeBuilder(
ci, new object[] { UnmanagedType.BStr });
// Apply the attribute to the parameter.
//
pb.SetCustomAttribute(cabuilder);
// Emit a dummy method body.
ILGenerator il = myMethod.GetILGenerator();
il.Emit(OpCodes.Ret);
Type finished = myType.CreateType();
myAssembly.Save(myAsmName.Name + ".dll");
}
}
Imports System
Imports System.Reflection
Imports System.Reflection.Emit
Imports System.Runtime.InteropServices
Public Class Example
Public Shared Sub Main()
Dim myDomain As AppDomain = AppDomain.CurrentDomain
Dim myAsmName As New AssemblyName("EmitMarshalAs")
Dim myAssembly As AssemblyBuilder = _
myDomain.DefineDynamicAssembly(myAsmName, _
AssemblyBuilderAccess.RunAndSave)
Dim myModule As ModuleBuilder = _
myAssembly.DefineDynamicModule(myAsmName.Name, _
myAsmName.Name & ".dll")
Dim myType As TypeBuilder = _
myModule.DefineType("Sample", TypeAttributes.Public)
Dim myMethod As MethodBuilder = _
myType.DefineMethod("Test", MethodAttributes.Public, _
Nothing, new Type() { GetType(String) })
' Get a parameter builder for the parameter that needs the
' attribute, using the HasFieldMarshal attribute. In this
' example, the parameter is at position 0 and has the name
' "arg".
Dim pb As ParameterBuilder = _
myMethod.DefineParameter(0, _
ParameterAttributes.HasFieldMarshal, "arg")
' Get the MarshalAsAttribute constructor that takes an
' argument of type UnmanagedType.
'
Dim ciParameters() As Type = { GetType(UnmanagedType) }
Dim ci As ConstructorInfo = _
GetType(MarshalAsAttribute).GetConstructor(ciParameters)
' Create a CustomAttributeBuilder representing the attribute,
' specifying the necessary unmanaged type. In this case,
' UnmanagedType.BStr is specified.
'
Dim ciArguments() As Object = { UnmanagedType.BStr }
Dim cabuilder As New CustomAttributeBuilder(ci, ciArguments)
' Apply the attribute to the parameter.
'
pb.SetCustomAttribute(cabuilder)
' Emit a dummy method body.
Dim il As ILGenerator = myMethod.GetILGenerator()
il.Emit(OpCodes.Ret)
myType.CreateType()
myAssembly.Save(myAsmName.Name & ".dll")
End Sub
End Class
Remarks
The code example shows the workaround for this obsolete type.
Marshaling is the process of packaging and unpackaging parameters so remote procedure calls can occur. During marshaling, a field might undergo a format conversion when the format of the managed type is different from the format of the corresponding unmanaged type. For example, you might want to marshal a String type as an unmanaged BSTR. Some format conversions are handled automatically by the runtime. To override the default behavior, you must use the UnmanagedMarshal class to define the format conversion.
Properties
| BaseType |
Gets an unmanaged base type. This property is read-only. |
| ElementCount |
Gets a number element. This property is read-only. |
| GetUnmanagedType |
Indicates an unmanaged type. This property is read-only. |
| IIDGuid |
Gets a GUID. This property is read-only. |
Methods
| DefineByValArray(Int32) |
Specifies a fixed-length array (ByValArray) to marshal to unmanaged code. |
| DefineByValTStr(Int32) |
Specifies a string in a fixed array buffer (ByValTStr) to marshal to unmanaged code. |
| DefineLPArray(UnmanagedType) |
Specifies an |
| DefineSafeArray(UnmanagedType) |
Specifies a |
| DefineUnmanagedMarshal(UnmanagedType) |
Specifies a given type that is to be marshaled to unmanaged code. |