在运行时生成对泛型方法的调用

Question

目标：在运行时生成这样的方法：

public void InsertOnSubmit<T>(IQueryable<T> q, T o) where T : class, new()
{
    (q as Table<T>).InsertOnSubmit(o);
}

我目前的代码是：

var tb = mb.DefineType("DatabaseDataRepository");

// define & implement other methods, etc

/* Define InsertOnSubmit<> method */
var insertOnSubmitMethod = tb.DefineMethod("InsertOnSubmit",
     MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.Virtual |
                    MethodAttributes.NewSlot);
var genericInput = insertOnSubmitMethod.DefineGenericParameters("T")[0];
                genericInput.SetGenericParameterAttributes(GenericParameterAttributes.ReferenceTypeConstraint | GenericParameterAttributes.DefaultConstructorConstraint);
                insertOnSubmitMethod.SetParameters(typeof(IQueryable<>).MakeGenericType(genericInput), genericInput);
insertOnSubmitMethod.SetReturnType(null);

/* Implement InsertOnSubmit<> method */
var saveMethodGen = insertOnSubmitMethod.GetILGenerator();
saveMethodGen.Emit(OpCodes.Ldarg_1); // push first argument (collection)
saveMethodGen.Emit(OpCodes.Isinst, typeof(Table<>).MakeGenericType(genericInput)); // cast first argument to Table<>
saveMethodGen.Emit(OpCodes.Ldarg_2); // push second argument (element)
saveMethodGen.Emit(OpCodes.Callvirt, typeof(Table<>).GetMethod("InsertOnSubmit")); // insert second argument to table
saveMethodGen.Emit(OpCodes.Ret); // return from InsertOnSubmit method

但是运行这个方法在生成的实例上我得到： An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B) 与堆栈 at DatabaseDataRepository.InsertOnSubmit[T](IQueryable`1 , T )

我怀疑这一行有问题 saveMethodGen.Emit(OpCodes.Callvirt, typeof(Table<>).GetMethod("InsertOnSubmit")); - 它真的应该像 typeof(Table<>).MakeGenericType(genericInput).GetMethod("InsertOnSubmit") - 但是这会抛出 NotSupportedException

有解决这个问题的提示吗？谢谢。

Answer 1

您必须使用静态 System.Reflection.Emit.Typebuilder.GetMethod 方法来创建正确键入的 MethodInfo。

msdn 声明：

Returns the method of the specified constructed generic type that corresponds to the specified method of the generic type definition.

你的情况是：

Typebuilder.GetMethod(typeof(Table<>).MakeGenericType(genericInput), typeof(Table<>).GetMethod("InsertOnSubmit"))

在运行时生成对泛型方法的调用

Generate call to generic method in runtime

c#

generics

reflection.emit