Question about Web Service Method Versioning

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I was under the impression that I could have multiple versions of the same
method (same signature) to support backward compatible clients. Is there a
versioning attribute that can be used?

For example:

[WebMethod()]
[Version=1.0.0.0]
public int Add(int x, int y)
{
return x + y;
}

[WebMethod()]
[Version=1.0.0.1]
public int Add(int x, int y)
{
return Math.Add(x,y);
}

I found only one article that addresses this at:

http://msdn2.microsoft.com/en-us/library/Aa480518.aspx

If anyone has any ideas on how this would be accomplished or have any
additional links to sites with samples, I would appreciate it.

Thanks in advance for your time.

dootndo2