Proper use of Substring and IndexOf Methods

Can someone please tell me how to extract a set of characters from a string.  For example, let say my string is:
"WebServer/AB=Test,CD=TESTING1,EF=TESTING2,GH=TESTING3"
I need to say find "CD" and tell me what it equals.  So my substring method would return "TESTING1"
Thanks so much,
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