Using the TryGet pattern in C# to clean up your code

Modern C# allows you to declare output variables inline; this has a subtle benefit of making TryFoo methods more attractive and cleaning up your code. Consider this:

public class FooCollection : ICollection<Foo>
{
  // ICollection<Foo> members omitted for brevity
  public Foo GetFoo(string fooIdentity)
  {
    return this.FirstOrDefault(foo => foo.Identity == fooIdentity);
  }
}

// somewhere else in the code
var foo = foos.GetFoo("dave");
if (foo != null)
{
  foo.Fight();
}

Our GetFoo method will return a default of Foo if one isn’t found that matches fooIdentity — code that uses this API needs to know that null indicates that no matching item was found. This isn’t unreasonably, but it does mean that we’re using two lines to find and assign our matching object. Instead, let’s try this approach:

public class FooCollection : ICollection<Foo>
{
  public bool TryGetFoo(string fooIdentity, out Foo fighter)
  {
    figher = this.FirstOrDefault(foo => foo.Identity == fooIdentity);
    return fighter != null;
  }
}

We’ve encoded the knowledge that null means “not found” directly into our method, and there’s no longer any ambiguity about whether we found our fighter or not. Our calling code can now be reduced by a line:

if (foos.TryGetFoo("dave", out foo))
{
  foo.Fight();
}

It’s not a huge saving on its own, but if you have a class of several hundred lines that’s making heavy use of the GetFoo method, this can save you a significant number of lines, and that’s always a good thing.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s