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c#delegateslambdainlineanonymous-function
user287107
user287107

Reputation: 9418

Func / Action delegates with reference arguments/parameters or anonymous functions

I just wondered, how the exact syntax is for ref and out parameters for delegates and inline lambda functions.

here is an example

if a function is defined as 

 public void DoSomething(int withValue) { }

a delegate in a function can be created by

 public void f()
 {   
     Action<int> f2 = DoSomething;
     f2(3);
 }

how is that syntax, if the original function would be defined as 

 public void DoSomething(ref int withValue) { withValue = 3; }

Upvotes: 7

Views: 6749

Answers (2)

Reed Copsey
Reed Copsey

Reputation: 564333

You can't use Action, Func<T>, or the built-in delegates, but need to define your own in this case:

delegate void ActionByRef<T>(ref T value);

Then, given this, you can have:

int value = 3;
ActionByRef<int> f2 = DoSomething;
f2(ref value);

Upvotes: 4

dtb
dtb

Reputation: 217233

You need to define a new delegate type for this method signature:

delegate void RefAction<in T>(ref T obj);

public void F()
{
    RefAction<int> f2 = DoSomething;
    int x = 0;
    f2(ref x);
}

The reason why the .NET Framework does not include this type is probably because ref parameters are not very common, and the number of needed types explodes if you add one delegate type for each possible combination.

Upvotes: 12

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