System.Reflection.Emit.MethodRental Class

Summary

Provides a fast way to swap method body implementation given a method of a class.

C# Syntax:

public sealed class MethodRental

Reflection Emit is thread-safe when using assemblies that were created with the AppDomain.DefineDynamicAssembly method with the Boolean parameter isSynchronized set to true.

System.Reflection.Emit Namespace

System.Reflection.Emit.MethodRental Member List:

Public Fields

JitImmediate	Specifies that the method should be just-in-time (JIT) compiled immediately.
JitOnDemand	Specifies that the method should be just-in-time (JIT) compiled when needed.

Public Methods

Equals (inherited from System.Object)	See base class member description: System.Object.Equals Derived from System.Object, the primary base class for all objects.
GetHashCode (inherited from System.Object)	See base class member description: System.Object.GetHashCode Derived from System.Object, the primary base class for all objects.
GetType (inherited from System.Object)	See base class member description: System.Object.GetType Derived from System.Object, the primary base class for all objects.
SwapMethodBody	Swaps the body of a method.
ToString (inherited from System.Object)	See base class member description: System.Object.ToString Derived from System.Object, the primary base class for all objects.

Protected Methods

Finalize (inherited from System.Object)	See base class member description: System.Object.Finalize Derived from System.Object, the primary base class for all objects.
MemberwiseClone (inherited from System.Object)	See base class member description: System.Object.MemberwiseClone Derived from System.Object, the primary base class for all objects.

Hierarchy:

• System.Object
• System.Reflection.Emit.MethodRental

System.Reflection.Emit.MethodRental Member Details

Summary

Specifies that the method should be just-in-time (JIT) compiled immediately.

C# Syntax:

public const int JitImmediate;

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Summary

Specifies that the method should be just-in-time (JIT) compiled when needed.

C# Syntax:

public const int JitOnDemand;

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Inherited
See base class member description: System.Object.Equals

C# Syntax:

public virtual bool Equals(    object obj );

For more information on members inherited from System.Object click on the link above.

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Inherited
See base class member description: System.Object.Finalize

C# Syntax:

~MethodRental();

For more information on members inherited from System.Object click on the link above.

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Inherited
See base class member description: System.Object.GetHashCode

C# Syntax:

public virtual int GetHashCode();

For more information on members inherited from System.Object click on the link above.

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Inherited
See base class member description: System.Object.GetType

C# Syntax:

public Type GetType();

For more information on members inherited from System.Object click on the link above.

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Inherited
See base class member description: System.Object.MemberwiseClone

C# Syntax:

protected object MemberwiseClone();

For more information on members inherited from System.Object click on the link above.

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Summary

Swaps the body of a method.

C# Syntax:

public static void SwapMethodBody(    Type cls,    int methodtoken,    IntPtr rgIL,    int methodSize,    int flags );

cls

The class containing the method.

methodtoken

The token for the method.

rgIL

A pointer to the method. This should include the method header.

methodSize

The size of the new method body in bytes.

flags

Flags that control the swapping. See the definitions of the constants.

Exceptions

Exception Type	Condition
ArgumentNullException	cls is null.
NotSupportedException	The type cls is not complete.

You cannot use this method to swap the body of a global method.

The method can only be called by the client that created the dynamic module that contains the type whose method's body is being swapped.

The following example illustrates how to swap a method body for a new body. It also illustrates how to obtain a method token for an existing method and how to construct a blob of bytes representing the Microsoft Intermediate Language (MSIL) code to be passed to SwapMethodBody.

using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.InteropServices;

class SwapMethodBodySample
{
    // First make a method that returns 0.
    // Then swap the method body with a body that returns 1.
    public static void Main(String [] args)
    {
    // Construct a dynamic assembly
    Guid g = Guid.NewGuid();    
    AssemblyName asmname = new AssemblyName();
    asmname.Name = "tempfile" + g;
    AssemblyBuilder asmbuild = System.Threading.Thread.GetDomain().
        DefineDynamicAssembly(asmname, AssemblyBuilderAccess.Run);

    // Add a dynamic module that contains one type that has one method that
    // has no arguments.
    ModuleBuilder modbuild = asmbuild.DefineDynamicModule( "test");
        TypeBuilder tb = modbuild.DefineType( "name of the Type" );
        MethodBuilder somemethod = tb.DefineMethod
            ("My method Name",
             MethodAttributes.Public | MethodAttributes.Static,
             typeof(int),                                                     
             new Type[]{} );
    // Define the body of the method to return 1.
        ILGenerator ilg = somemethod.GetILGenerator();
    ilg.Emit(OpCodes.Ldc_I4_0);
    ilg.Emit(OpCodes.Ret);

    // Complete the type and verify that it returns 0.
    Type tbBaked = tb.CreateType();
    int res1 = (int)tbBaked.GetMethod("My method Name").Invoke( null, new Object[]{} );
    if ( res1 != 0 ) {
        Console.WriteLine( "Err_001a, should have returned 1" );
    } else {
        Console.WriteLine("Original method returned 0");
    }
                
    // Define a new method body that will return a 1 instead.
    Byte[] methodBytes = {
        0x03,
        0x30,
        0x0A,
        0x00,
        0x02,                // code size
        0x00,
        0x00,
        0x00,
        0x00,
        0x00,
        0x00,
        0x00,
        0x17,                // ldc_i4_1
        0x2a                // ret
    };

    // Get the token for the method whose body you are replacing.
    MethodToken somemethodToken = somemethod.GetToken();        

    // Get the pointer to the method body.
        GCHandle hmem = GCHandle.Alloc((Object) methodBytes, GCHandleType.Pinned);
        IntPtr addr = hmem.AddrOfPinnedObject();
    int cbSize = methodBytes.Length;

    // Swap the old method body with the new body.
    MethodRental.SwapMethodBody(
                    tbBaked, 
                    somemethodToken.Token, 
                    addr,
                    cbSize,
                    MethodRental.JitImmediate);

    // Verify that the modified method returns 1.
    int res2 = (int)tbBaked.GetMethod("My method Name").Invoke( null, new Object[]{} );
    if ( res2 != 1 ) {
        Console.WriteLine( "Err_001b, should have returned 1" );
    } else {
        Console.WriteLine("Swapped method body returned 1");
    }
    }
}

    

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Inherited
See base class member description: System.Object.ToString

C# Syntax:

public virtual string ToString();

For more information on members inherited from System.Object click on the link above.

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