public void Modify(AssemblyDefinition assembly)
{
var mainModule = assembly.MainModule;
var getInterceptorMethod = mainModule.Import(typeof(InterceptorRegistry).GetMethod(nameof(InterceptorRegistry.GetInterceptor)));
var interceptMethod = mainModule.Import(typeof(IInterceptor).GetMethod(nameof(IInterceptor.Intercept)));
var objectReference = mainModule.Import(typeof(object));
var getMethodFromHandle =
mainModule.Import(typeof(MethodBase).GetMethod(nameof(MethodBase.GetMethodFromHandle),
new Type[] { typeof(RuntimeMethodHandle), typeof(RuntimeTypeHandle) }));
var targetType = mainModule.Types.FirstOrDefault(t => t.Name == "SampleClassWithInstanceMethod");
if (targetType == null)
{
return;
}
var targetMethod = targetType.Methods.First(m => m.Name == "DoSomething");
var methodBody = targetMethod.Body;
var IL = methodBody.GetILProcessor();
var instructions = methodBody.Instructions.ToArray();
methodBody.Instructions.Clear();
var argsArray = targetMethod.AddLocal <object[]>();
foreach (var instruction in instructions)
{
if (instruction.OpCode != OpCodes.Call)
{
IL.Append(instruction);
continue;
}
var methodCall = ((MethodReference)instruction.Operand);
var parameterCount = methodCall.Parameters.Count;
var localParameters = new VariableDefinition[parameterCount];
var thisParameter = targetMethod.AddLocal <object>();
for (int i = 0; i < parameterCount; i++)
{
localParameters[i] = targetMethod.AddLocal <object>();
if (methodCall.Parameters[i].ParameterType.IsValueType)
{
IL.Emit(OpCodes.Box, methodCall.Parameters[i].ParameterType);
}
IL.Emit(OpCodes.Stloc, localParameters[i]);
}
if (!methodCall.Resolve().IsStatic)
{
IL.Emit(OpCodes.Stloc, thisParameter);
}
else
{
IL.Emit(OpCodes.Ldnull);
IL.Emit(OpCodes.Stloc, thisParameter);
}
IL.Emit(OpCodes.Call, getInterceptorMethod);
IL.Emit(OpCodes.Ldc_I4, parameterCount);
IL.Emit(OpCodes.Newarr, objectReference);
IL.Emit(OpCodes.Stloc, argsArray);
int j = 0;
foreach (var variableDefinition in localParameters.Reverse())
{
IL.Emit(OpCodes.Ldloc, argsArray);
IL.Emit(OpCodes.Ldc_I4, j++);
IL.Emit(OpCodes.Ldloc, variableDefinition);
IL.Emit(OpCodes.Stelem_Ref);
}
IL.Emit(OpCodes.Ldloc, thisParameter);
IL.Emit(OpCodes.Ldloc, argsArray);
IL.Emit(OpCodes.Ldtoken, methodCall);
IL.Emit(OpCodes.Ldtoken, methodCall.DeclaringType);
IL.Emit(OpCodes.Call, getMethodFromHandle);
IL.Emit(OpCodes.Callvirt, interceptMethod);
if (methodCall.ReturnType.MetadataType == MetadataType.Void)
{
IL.Emit(OpCodes.Pop);
}
else
{
IL.Emit(OpCodes.Unbox_Any, methodCall.ReturnType);
}
}
}