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How to wrap existing object instance into DispatchProxy?

I'm looking for RealProxy replacement in .NET Core, and this issue forwards me to DispatchProxy.
It has simple API, but it's unclear, how to wrap existing object into proxy.
E.g., having this interface:
interface IFoo
{
string Bar(int boo);
}
and this implementation:
class FooImpl : IFoo
{
public string Bar(int boo)
{
return $"Value {boo} was passed";
}
}
how to get what I want?
class Program
{
static void Main(string[] args)
{
var fooInstance = new FooImpl();
var proxy = DispatchProxy.Create<IFoo, FooProxy>();
var s = proxy.Bar(123);
Console.WriteLine(s);
}
}
class FooProxy : DispatchProxy
{
protected override object Invoke(MethodInfo targetMethod, object[] args)
{
return targetMethod.Invoke(/* I need fooInstance here */, args);
}
}
Since DispatchProxy descendants must have parameterless constructor, the only idea I have is to invent some method, like this:
class FooProxy : DispatchProxy
{
private object target;
public void SetTarget(object target)
{
this.target = target;
}
protected override object Invoke(MethodInfo targetMethod, object[] args)
{
return targetMethod.Invoke(target, args);
}
}
and use it this way:
var fooInstance = new FooImpl();
var proxy = DispatchProxy.Create<IFoo, FooProxy>();
((FooProxy)proxy).SetTarget(fooInstance);
// the rest of code...
Is this correct approach?

You are right that there is no other option here than to cast the generated IFoo to the known proxy type (FooProxy) and use a custom method or property on FooProxy. There is no public API to add constructor arguments or return the proxy as the implementation type. However, DispatchProxy.Create() will return an instance of a subclass of FooProxy whose type is generated at runtime via reflection and IL emitting.
If you are looking at other ways to quickly wrap an implementation and replace interface methods / virtual methods, I suggest using mocking frameworks instead (FakeItEasy, Moq, NSubstitute etc.).

You need to create your own Generic class that inherit from DispatchProxy and has own static Create that has an extra parameter from type target.
example
public class AopAction<T>:DispatchProxy
{
#region Private Fields
private Action<MethodInfo,object[],object> ActAfter;
private Action<MethodInfo,object[]> ActBefore;
private Action<MethodInfo,object[],Exception> ActException;
private T Decorated;
#endregion Private Fields
#region Public Methods
public static T Create(T decorated,Action<MethodInfo,object[]> actBefore = null,Action<MethodInfo,object[],object> actAfter = null,Action<MethodInfo,object[],Exception> actException = null)
{
object proxy = Create<T,AopAction<T>>();
SetParameters();
return (T)proxy;
void SetParameters()
{
var me = ((AopAction<T>)proxy);
me.Decorated = decorated == null ? throw new ArgumentNullException(nameof(decorated)) : decorated;
me.ActBefore = actBefore;
me.ActAfter = actAfter;
me.ActException = actException;
}
}
#endregion Public Methods
#region Protected Methods
protected override object Invoke(MethodInfo targetMethod,object[] args)
{
_ = targetMethod ?? throw new ArgumentException(nameof(targetMethod));
try
{
ActBefore?.Invoke(targetMethod,args);
var result = targetMethod.Invoke(Decorated,args);
ActAfter?.Invoke(targetMethod,args,result);
return result;
}
catch(Exception ex)
{
ActException?.Invoke(targetMethod,args,ex);
throw ex.InnerException;
}
}
#endregion Protected Methods
}
to use your example
var proxy=AopAction<IFoo>.Create(new FooImpl());

How can i get the parameter values of an anonymous method passed as a func?

I am calling methods on a remote system. The remote system implements an interface that both systems have a copy of (via shared nuget repository). At the moment i am sending the requests like this:
var oldRequest = new FooRequest("GetEmployeeById", new object[] { "myPartner", 42, DateTime.Now.AddDays(-1) });
Here is the interface:
public class FooResponse<T> { }
public interface IFooController
{
FooResponse<string> GetEmployeeById(string partnerName, int employeeId, DateTime? ifModifiedSince);
}
As you can image, sometimes programmers passes arguments in the wrong order to the array in the constructor, and things start to fail. To resolve this I have created the following code to have intellisense support when creating the FooRequest:
public static FooRequest Create<T>(Func<FooResponse<T>> func)
{
return new FooRequest(null, null); // Here goes some magic reflection stuff instead of null.
}
It is now possible to create a FooRequest like this:
public static IFooController iFooController => (IFooController)new object();
public static FooRequest CreateRequest<T>(Func<FooResponse<T>> func)
{
return FooRequest.Create(func);
}
var newRequest = CreateRequest(() => iFooController.GetEmployeeById("myPartner", 42, DateTime.Now.AddDays(-1)));
My question then is: How will i be able to get the name of the method and the value of the parameters in the FooRequest.Create-method?
I have exhausted both my reflection and google-skills trying to find the values, but no luck so far.
Complete compiling code can be found here if someone wants to give it a shot: http://ideone.com/ovWseI

Here is a sketch of how you can do this with expressions:
public class Test {
public static IFooController iFooController => (IFooController) new object();
public static FooRequest CreateRequest<T>(Expression<Func<FooResponse<T>>> func) {
return FooRequest.Create(func);
}
public static void Main() {
var newRequest = CreateRequest(() => iFooController.GetEmployeeById("myPartner", 42, DateTime.Now.AddDays(-1)));
Console.ReadKey();
}
}
public class FooRequest {
public static FooRequest Create<T>(Expression<Func<FooResponse<T>>> func) {
var call = (MethodCallExpression) func.Body;
var arguments = new List<object>();
foreach (var arg in call.Arguments) {
var constant = arg as ConstantExpression;
if (constant != null) {
arguments.Add(constant.Value);
}
else {
var evaled = Expression.Lambda(arg).Compile().DynamicInvoke();
arguments.Add(evaled);
}
}
return new FooRequest(call.Method.Name, arguments.ToArray());
}
public FooRequest(string function, object[] data = null) {
//SendRequestToServiceBus(function, data);
Console.Write($"Function name: {function}");
}
}
public class FooResponse<T> {
}
public interface IFooController {
FooResponse<string> GetEmployeeById(string partnerName, int employeeId, DateTime? ifModifiedSince);
}

pass value through custom attribute for method access

Can any one please tell me about custom attribute for method.I need to pass a string to attribute.If the string is true then i will access the method otherwise don't access the method.

I am not sure, if I understood your question wrongly. But are you talking about following kind of attribute which decorates the method. I had created this code when I was exploring attributes. I am pasting it here. Hope it helps.
In this, I have created the attribute, [Allow("Valid")] if it is valid we can call the method , else not.
namespace ConsoleApplication1
{
using System;
[AttributeUsage(AttributeTargets.All)]
public class AllowAttribute : System.Attribute
{
public readonly string SomeString;
public AllowAttribute(string someString) // your string is passed in custom attribute
{
this.SomeString = someString;
}
}
public interface IAllowAttributeInvoker
{
object AllowAttributeInvokeMethod<T>(string methodName, T classInstance, object[] parametersArray);
}
public class AllowAttributeInvoker: IAllowAttributeInvoker
{
public object AllowAttributeInvokeMethod<T>(string methodName, T classInstance, object[] parametersArray)
{
System.Reflection.MemberInfo info = typeof(T).GetMethod(methodName);
if (IsAttributeValid(info))
{
var method = (typeof (T)).GetMethod(methodName);
Console.WriteLine("Invoking method");
var result = method.Invoke(classInstance, parametersArray);
return result;
}
else
{
Console.WriteLine("Can not invoke this method.");
}
return null;
}
private static bool IsAttributeValid(MemberInfo member)
{
foreach (object attribute in member.GetCustomAttributes(true))
{
if (attribute is AllowAttribute && ((AllowAttribute)attribute).SomeString == "Valid")
{
return true;
}
}
return false;
}
}
public class EmployeeService :AllowAttributeInvoker
{
public object PaySalary()
{
return AllowAttributeInvokeMethod("PaySalaryInvoke", this, null);
}
[Allow("Valid")]
public void PaySalaryInvoke()
{
Console.WriteLine("Salary Paid.");
}
}
class Program
{
static void Main(string[] args)
{
Console.ReadLine();
EmployeeService service = new EmployeeService();
service.PaySalary();
Console.ReadLine();
}
}
}

1-You can define public user access list:
public List<string> AccessRules = new List<string>();
2-Set user access rules in constructor :
AccessRules.AddRange(new[] { "GetCurrentDateTime", "GetCurrentDate" });
3-In secure methods check user access rule
public DateTime GetCurrentDateTime()
{
bool haveAccess = AccessRules.Any(c => c == "GetCurrentDateTime");
if (haveAccess)
{
return DateTime.Now;
}
return null;
}

Unit Testing of a static factory method containing logic

before I begin with my question I want to point out that I am aware that there are tons of similar questions on stack overflow. Unfortunately none of these questions helped me finding a good solution in my concrete scenario.
The Problem:
I want to write a unit test for a static factory method which contains logic. I am looking for a way to unit test this method even if it is static. If that is not possible maybe someone can point out a better design for my class under test. I also considered using IoC but couldn't see the advantage considering unit-testing.
The Code:
public class Db
{
private XmlMapping mapping;
public static Db<T> Create()
{
var mapping = XmlMapping.Create(typeOf(T).Name);
return new Db(mapping);
}
private Db(XmlMapping mapping)
{
this.mapping = mapping;
}
}
public class XmlMapping //class under test
{
public static XmlMapping Create(string filename) //method under test
{
try
{
ValidateFilename(filename);
//deserialize xml to object of type XmlMapping
var result = Deserialize(filename);
if (result.IsInValid())
throw Exception()
return result;
}
catch (Exception)
{
throw new DbException();
}
}
}
The method Create which I want to unit test is within the class XmlMapping. This method serializes a xml file and generates an object of type XmlMapping. I tried to write a stub for the serialization part. But didn't want to call my Database Factory with a Mapping class in the constructor (constructor injection).
Edit:
My database factory is generic. The generic type is used to figure out which xml file should be louded i.e.: typeOf(T) = Customer --> XmlMapping-File = Customer.xml
The Solution (Thx to Jeff!):
public class XmlMapping : IMapping //class under test
{
internal static Func<Type, IMapping> DeserializeHandler { get; set; }
static XmlMapping()
{
DeserializeHandler = DeserializeMappingFor;
}
public static IMapping Create(Type type)
{
try
{
var mapping = DeserializeHandler(type);
if (!mapping.IsValid())
throw new InvalidMappingException();
return mapping;
}
catch (Exception ex)
{
throw new DataException("Failed to load mapping configuration from xml file.", ex);
}
}
internal XmlMapping(IMapping mapping)
{
this.Query = mapping.Query;
this.Table = mapping.Table;
this.Entity = mapping.Entity;
this.PropertyFieldCollection = mapping.PropertyFieldCollection;
}
private XmlMapping() { }
}
[TestClass]
public class MappingTests //testing class
{
[TestMethod]
public void Create_ValidDeserialization_ReturnsObjectInstance()
{
XmlMapping.DeserializeHandler = MakeFakeHandlerFor(MakeMappingStub());
var result = XmlMapping.Create(typeof(ActivityDto));
Assert.IsInstanceOfType(result, typeof(XmlMapping));
}
}

I would use a fake action handler to assist in verifying the content of the call to deserialize. Let's add a Func delegate property and default that to your serialize method. Your XmlMapping class and test would like something like:
public class XmlMapping //class under test
{
static XmlMapping()
{
// Default the handler to the normal call to Deserialize
DeserializeHandler = Deserialize;
}
public static XmlMapping Create(string filename) //method under test
{
//deserialize xml to object of type XmlMapping
//preudocode:
var result = DeserializeHandler(string.Format("{0}.xml",filename));
//...
return result;
}
// Abstract indirection function to allow you to swap out Deserialize implementations
internal static Func<string, XmlMapping> DeserializeHandler { get; set; }
private static XmlMapping Deserialize(string fileName)
{
return new XmlMapping();
}
}
public class CreateTests {
public void CallingDeserializeProperly()
{
// Arrange
var called = false;
Func<string, XmlMapping> fakeHandler = (string f) =>
{
called = true; // do your test of the input and put your result here
return new XmlMapping();
};
// Act
XmlMapping.DeserializeHandler = fakeHandler;
var m = XmlMapping.Create("test");
// Assert
Assert.IsTrue(called);
}
}

Rhino Mocks Exception Expect #1 Actual #0 : Need assistance

I've have searched on this and it seems to be a catch all, unfortunately everything I've read doesn't help figure it out. Here is the class:
public interface IMockInterface
{
MockClass MockedMethod();
MockClass MockThis();
}
public class MockClass : IMockInterface
{
public virtual MockClass MockedMethod()
{
MockClass returnValue;
returnValue = new MockClass();
returnValue.SomeMessage = "Not mocked";
return returnValue;
}
public MockClass MockThis()
{
MockClass mock;
MockClass returnValue;
mock = new MockClass();
return mock.MockedMethod();
}
}
And the test:
public void MockTest_Internal()
{
MockClass mainClass;
MockClass returnedClass;
IMockInterface mockProvider;
mainClass = new MockClass();
mockProvider = repository.StrictMock<IMockInterface>();
Expect.Call(mockProvider.MockedMethod())
.Return(new MockClass { SomeMessage = "Mocked" });
repository.ReplayAll();
returnedClass = mainClass.MockThis();
provider.AssertWasCalled(item => item.MockedMethod());
Assert.IsTrue(returnedClass.SomeMessage == "Mocked");
}
And have also tried and doesn't work
But I keep getting this exception:
Rhino.Mocks.Exceptions.ExpectationViolationException:
IMockInterface.MockedMethod(); Expected #1, Actual #0
Now from what I've read this would suggest either the method was called with different than expected parameters OR the method was never called but was expected to be called. This isn't the case for the test.
Side Note: This is my first time really using Rhino.Mocks without some in house code so I am basically picking it up as I go. There could be something really stupid here...
This was the old test commented on, but is not what I should have been using:
public void MockTest_Internal()
{
MockClass mainClass;
MockClass returnedClass;
IMockInterface mockProvider;
mainClass = new MockClass();
var provider = MockRepository.GenerateStub<IMockInterface>();
provider.Stub(item => item.MockedMethod())
.Return(new MockClass { SomeMessage = "Mocked" });
returnedClass = mainClass.MockThis();
provider.AssertWasCalled(item => item.MockedMethod());
Assert.IsTrue(returnedClass.SomeMessage == "Mocked");
}

You're telling the mock framework to stub the MockedMethod class on the provider object, but you never inject the provider into the mainClass object to be used. It's not clear to me what you are trying to accomplish but if you want the mocked method to be called then it has to be called on the object on which the stub was set up.
If you define MockThis as below, I think you will find that it will work.
public MockClass MockThis(IMockInterface provider)
{
return provider.MockMethod();
}
The bottom line is that you get the exception because the method was never called on the provider, only on the mainClass object.
EDIT: Example
public class ClassUnderTest
{
private ProviderClass provider { get; set; }
public ClassUnderTest( ProviderClass provider )
{
this.Provider = provider;
}
public int DoOperation()
{
return this.Provider.ProviderOperation();
}
}
public class ProviderClass
{
private int value = 42;
public ProviderClass()
{
}
public virtual int ProviderOperation()
{
return this.value;
}
}
[TestMethod]
public void DoOperationTest()
{
ProviderClass mockProvider = MockRepository.GenerateMock<ProviderClass>();
mockProvider.Expect( mp => mp.ProviderOperation() ).Return( -1 );
ClassUnderTest target = new ClassUnderTest( mockProvider );
int expectedValue = -1;
int value = target.DoOperation();
Assert.AreEqual( expectedValue, value );
mockProvider.VerifyAllExpectations();
}
Normally the ProviderClass object would return 42 from the ProviderOperation method, but we've mocked it out and told it to return -1. When the ClassUnderTest DoOperation method is called, the mock provider object's ProviderOperation method is invoked and returns the mocked value of -1.
Hope this helps.

I usually get this error when a stubbed method is called with an object argument that I build in the test and in the tested code the object is built before calling that method. The solution is to use the Rhino.Mocks Matches().
Ex:
Arg<string>.Matches(s => s.Contains("some substring"))