在运行时生成对通用方法的调用

时间:2019-07-18 10:59:30

标签: c# generics reflection.emit

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);
}

我当前的代码是:

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

但是在生成的实例上运行此方法,我得到: An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B),堆栈为at DatabaseDataRepository.InsertOnSubmit[T](IQueryable`1 , T )

我怀疑此行saveMethodGen.Emit(OpCodes.Callvirt, typeof(Table<>).GetMethod("InsertOnSubmit"));中有问题-确实应该是typeof(Table<>).MakeGenericType(genericInput).GetMethod("InsertOnSubmit")之类的东西-但这会抛出NotSupportedException

有什么办法解决吗? 谢谢。

1 个答案:

答案 0 :(得分: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指出:

  

返回与通用类型定义的指定方法相对应的指定构造通用类型的方法。

在您的情况下,将是:

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