[Adan]

What is the best practice to re-generate WSDL

[Adan]

You cannot edit your vendor’s WSDL. Those changes have to be made from their side. You will then generate new C# web service proxy classes from the new WSDL which they publish.

If you really have to…
What you can do however, is to manually generate the C# web service client proxy manually, pointing it to the WSDL file which you have modified. You do this with the WSDL.EXE tool (Open a Visual Studio Command Line) and then use this new class in place of the one you generated by adding a service reference in your Visual Studio.

wsdl.exe PathToYourFile.wsdl /l:CS /serverInterface

Use VB or CS for your language of choice. This will create a new .cs or .vb file

NOTE: Typically, what you see in the WSDL on the url provided by your vendor is an WSDL that is automatically generated from a tool that analyses their code. As such, your changes might in fact not be supported yet by the web service that you are consuming.