How do you declare a Predicate Delegate inline?

There's two options, an explicit delegate or a delegate disguised as a lamba construct:

explicit delegate

myObjects.RemoveAll(delegate (MyObject m) { return m.X >= 10; });

lambda

myObjects.RemoveAll(m => m.X >= 10);

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Performance wise both are equal. As a matter of fact, both language constructs generate the same IL when compiled. This is because C# 3.0 is basically an extension on C# 2.0, so it compiles to C# 2.0 constructs

  //C# 2.0
  RemoveAll(delegate(Foo o){ return o.X >= 10; });

or

  //C# 3.0
  RemoveAll(o => o.X >= 10);

or

  Predicate<Foo> matches = delegate(Foo o){ return o.X >= 10; });
  //or Predicate<Foo> matches = o => o.X >= 10;
  RemoveAll(matches);

The lambda C# 3.0 way:

myObjects.RemoveAll(m => m.x >= 10);

The anonymous delegate C# 2.0 way:

myObjects.RemoveAll(delegate (MyObject m) {
   return m.x >= 10;
});

And, for the VB guys, the VB 9.0 lambda way:

myObjects.RemoveAll(Function(m) m.x >= 10)

Unfortunately, VB doesn't support an anonymous delegate.