public static Action <object, IDataReader, int> CreateSetValueFromReaderDelegate(MemberInfo member)
{
Action <object, IDataReader, int> del = null;
DynamicMethod dm = new DynamicMethod("SetValueFromReader_" + Guid.NewGuid().ToString("N"), null, new Type[] { typeof(object), typeof(IDataReader), typeof(int) }, true);
ILGenerator il = dm.GetILGenerator();
il.Emit(OpCodes.Ldarg_S, 0); //将第一个参数 object 对象加载到栈顶
il.Emit(OpCodes.Castclass, member.DeclaringType); //将 object 对象转换为强类型对象 此时栈顶为强类型的对象
var readerMethod = DataReaderConstant.GetReaderMethod(member.GetMemberType());
//ordinal
il.Emit(OpCodes.Ldarg_S, 1); //加载参数DataReader
il.Emit(OpCodes.Ldarg_S, 2); //加载 read ordinal
il.EmitCall(OpCodes.Call, readerMethod, null); //调用对应的 readerMethod 得到 value reader.Getxx(ordinal); 此时栈顶为 value
EmitHelper.SetValueIL(il, member); // object.XX = value; 此时栈顶为空
il.Emit(OpCodes.Ret); // 即可 return
del = (Action <object, IDataReader, int>)dm.CreateDelegate(typeof(Action <object, IDataReader, int>));
return(del);
}