Equivalent of typedef in C#

c# typedef
Matthew Scharley picture Matthew Scharley · Oct 2, 2008 · Viewed 209.7k times · Source

Is there a typedef equivalent in C#, or someway to get some sort of similar behaviour? I've done some googling, but everywhere I look seems to be negative. Currently I have a situation similar to the following:

class GenericClass<T> 
{
    public event EventHandler<EventData> MyEvent;
    public class EventData : EventArgs { /* snip */ }
    // ... snip
}

Now, it doesn't take a rocket scientist to figure out that this can very quickly lead to a lot of typing (apologies for the horrible pun) when trying to implement a handler for that event. It'd end up being something like this:

GenericClass<int> gcInt = new GenericClass<int>;
gcInt.MyEvent += new EventHandler<GenericClass<int>.EventData>(gcInt_MyEvent);
// ...

private void gcInt_MyEvent(object sender, GenericClass<int>.EventData e)
{
    throw new NotImplementedException();
}

Except, in my case, I was already using a complex type, not just an int. It'd be nice if it were possible to simplify this a little...

Edit: ie. perhaps typedefing the EventHandler instead of needing to redefine it to get similar behaviour.

Answer

Jon Skeet picture Jon Skeet · Oct 2, 2008

No, there's no true equivalent of typedef. You can use 'using' directives within one file, e.g.

using CustomerList = System.Collections.Generic.List<Customer>;

but that will only impact that source file. In C and C++, my experience is that typedef is usually used within .h files which are included widely - so a single typedef can be used over a whole project. That ability does not exist in C#, because there's no #include functionality in C# that would allow you to include the using directives from one file in another.

Fortunately, the example you give does have a fix - implicit method group conversion. You can change your event subscription line to just:

gcInt.MyEvent += gcInt_MyEvent;

:)

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