lowlevel socket programming

Code:

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private System.Net.Sockets.Socket mySock = null;

mySock.Connect(...);

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this code seems to me like trash because I only can
set the destination IP parameter.

I want to set the source IP parameter too, but it seems like
the constructor of that class uses the IP of the host that sends that request.

any other idea how to define the source IP?

thx!