What is the difference (if any) between "yield" and "yield return" in C#?

I've traditionally used yield in C# without the return, e.g.:

IEnumerable<T> Foobar() {
   foreach( var foo in _stuff ) {
      yield foo;
   }
}

But in other examples I've seen it written as "yield return foo;", see: http://msdn.microsoft.com/en-us/library/9k7k7cf0%28VS.8开发者_高级运维0%29.aspx.

Is there any difference?

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C# does not allow yield all by itself - only yield return and yield break.

yield is a contextual keyword that is only recognized inside iterator blocks and only in conjunction with either return or break.