Need help creating extension method in C# with generics and lambda expression

Question

I'm pulling all of the advanced features together for this one, but haven't worked with generics or lambda expressions very much:

Here's example usage of the method I want to create:

MyClass mc = null;
int x = mc.TryGetOrDefault(z => z.This.That.TheOther); // z is a reference to mc
// the code has not failed at this point and the value of x is 0 (int's default)
// had mc and all of the properties expressed in the lambda expression been initialized
// x would be equal to mc.This.That.TheOther's value

Here's as far as I've gotten, but Visual Studio is complaining:

Jon Skeet · Accepted Answer · 2011-07-19 20:11:41Z

5

You haven't made your method generic in TResult. You want something like:

public static TResult TryGetOrDefault<TSource, TResult>
    (this TSource obj, Expression<Func<TSource, TResult>> expression)

answered Jul 19, 2011 at 20:11

Jon Skeet

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4 Comments

Jamie Dixon Over a year ago

You've just made this into an entirely new question Ronnie. I think Jon has answered the first one perfectly.

Ronnie Overby Over a year ago

I thought the scope of the question centered around my end result and since StackOverflow touts itself as being wiki like, I could update the question. Wait for URL to my next ?

Jon Skeet Over a year ago

@Ronnie: You can edit an existing question - but you've asked a new question, which isn't the same thing at all.

Ronnie Overby Over a year ago

Got it. Thanks for the help. I asked another question.

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