//引入命名空间
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 0.
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 0" );
} 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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