You need to change the way the request is made. Either complete your request string by adding =""
to the end, or leave out the BuildTypeName
parameter when it is empty.
So you get either of these two cases:
/api/BuildTypeWebApi/GetBuildTypeList?CurrPage=1&PageSize=10&BuildTypeName=""
/api/BuildTypeWebApi/GetBuildTypeList?CurrPage=1&PageSize=10
This way, Web API actually knows what you want to do with the BuildTypeName parameter. In your case it was an incomplete request.