How do I fix 'cannot convert from method group to 'Func'?

Question

try
    {
      var login = ToServiceLogin(lgParameters);
      await Task.Factory.FromAsync(loginOperation.BeginLogin,
loginOperation.EndLogin, lgParameters, TaskCreationOptions.None);

    }
    catch (FaultException fe)
    {
        Debug.WriteLine(@"          {0}", fe.Message);
    }
    catch (Exception ex)
    {
        Debug.WriteLine(@"              ERROR {0}", ex.Message);
    }

Compile error occurs on the first parameter of Task.Factory.FromAsync. I've read up on a couple of threads regarding similar issue none seems to be helping they all refer to this having a different signature. Please point me to the right direction.

EDIT With Signature

BeginLogin Signature

IAsyncResult BeginLogin(PRPClockingXamarin.PRPServiceMobile.LoginParameters loginParams,
                         AsyncCallback callback, object asyncState);

What's the type of `BeginLogin`, `EndLogin` and `lgParameters`? I would start by specifying the type parameters to `FromAsync` to get a more specific error message. — Lee, Jan 09 '17 at 10:32
It's clear form the error that BeginLogin does not have the right signature. — H H, Jan 09 '17 at 10:33
Please include the signature of `BeginLogin` and `EndLogin` so that it's easier to provide a meaningful answer. — spender, Jan 09 '17 at 10:34
The type for loginOperation is the interface of my WCF service. — Lord-David, Jan 09 '17 at 10:34

H H · Accepted Answer · 2017-01-09T13:03:29.717

3

There is a long terse list of overloads but it seems it won't match your

IAsyncResult BeginLogin(
    LoginParameters loginParams,
    AsyncCallback callback, 
    object asyncState);

as the argument for

  Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,

So I would suggest specifying the Type argument for Targ1,

FromAsync<PRPClockingXamarin.PRPServiceMobile.LoginParameters> (...)

also verify that lgParameters is of the correct type.

edited Jan 09 '17 at 13:03

answered Jan 09 '17 at 11:00

H H

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This worked I no longer have the error, thank you. The issue now is that it says my LoginResponse has the wrong return type. Any Idea where I could be going wrong? – Lord-David Jan 09 '17 at 11:23
I don't see any LoginResponse – H H Jan 09 '17 at 11:30
LoginResponse is part of the EndLogin signature PRPClockingXamarin.PRPServiceMobile.LoginResponse EndLogin(System.IAsyncResult result); – Lord-David Jan 09 '17 at 11:35
1

I think you need yet another overload, [`FromAsync(Func, Func, TArg1, Object, TaskCreationOptions)`](https://msdn.microsoft.com/en-us/library/dd321447(v=vs.110).aspx) . – H H Jan 09 '17 at 11:59

score 0 · Answer 2 · answered Jan 09 '17 at 15:12

When using FromAsync, I usually recommend setting up the parameters as: begin method, end method, begin method arguments (except callback/state), and null. The final null is for the state:

await Task.Factory.FromAsync(loginOperation.BeginLogin, loginOperation.EndLogin,
    lgParameters, null);

How do I fix 'cannot convert from method group to 'Func'?

2 Answers2

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