Checks the user database whether the given username/password combination is a valid user account. Returns a data set that contains all information about a given user. The LEAD UserService provides minimal interaction with the web service user database. Its purpose is to query for the status of a user account or to get information about a user account.<br><br><a href='http://www.leadtools.net/sdk/SDK%20Help/UserService/index.htm' target='_blank'>User Service Online SDK Documentation</a><br><a href='http://www.leadtools.net/sdk/SDK%20Tutorials/ASP%20.NET/Getting%20Started.htm' target='_blank'>ASP.NET Tutorial</a><br><a href='http://www.leadtools.net/sdk/SDK%20Tutorials/Windows/Getting%20Started.htm' target='_blank'>Windows Forms Tutorial</a>