public static Delegate ConstructorCaller(Type delegateType, ConstructorInfo constructor, Type instanceType)
{
// arguments checks
if (!typeof(Delegate).IsAssignableFrom(delegateType))
{
throw new ArgumentException("delegateType does not represents a delegate", nameof(delegateType));
}
if (instanceType == null && !instanceType.IsValueType)
{
throw new ArgumentNullException(nameof(instanceType));
}
if (constructor == null && !instanceType.IsValueType)
{
throw new ArgumentException("constructor is null, but instanceType is not a value type", nameof(instanceType));
}
// read delegate info
var methodInfo = delegateType.GetMethod("Invoke");
var delegateArgs = methodInfo.GetParameters().Select(x => x.ParameterType).ToArray() ?? Type.EmptyTypes;
var retType = methodInfo.ReturnType != typeof(void) ? methodInfo.ReturnType : null;
// read constructor info
var ctorArgs = constructor?.GetParameters().Select(x => x.ParameterType).ToArray() ?? Type.EmptyTypes;
if (delegateArgs.Length != ctorArgs.Length)
{
throw new Exception("deletage's arguments count does not match constructor's arguments count");
}
//
var targetType = constructor?.DeclaringType ?? instanceType;
DynamicMethod wrapper = new DynamicMethod($"ctor_{targetType.Name}_", retType, delegateArgs, typeof(Dynamic), true);
IILGenerator gen = wrapper.GetILGenerator().AsInterface();
if (targetType.IsValueType && ctorArgs.Length == 0)
{
CreateInitValueType(targetType, gen);
}
else
{
List <ILArgBuilder> argBuilders = new List <ILArgBuilder>();
for (int i = 0; i < ctorArgs.Length; i++)
{
argBuilders.Add(ILMethodBuilder.GetArgBuilder(gen, delegateArgs[i], ctorArgs[i]));
}
for (int i = 0; i < ctorArgs.Length; i++)
{
argBuilders[i].Prepare((byte)i);
}
for (int i = 0; i < ctorArgs.Length; i++)
{
argBuilders[i].PassArg((byte)i);
}
gen.Newobj(constructor);
for (int i = ctorArgs.Length - 1; i >= 0; i--)
{
argBuilders[i].Finalize_((byte)i);
}
}
gen.Ret();
return(wrapper.CreateDelegate(delegateType));
}