Repeatedly prompt for username/password when adding Service Reference to SharePoint site from VS2010

I am developing a simple C# winform application which retrieves lists from a SharePoint site. But I encountered a problem when I tried to add service reference to that sharepoint site in VS2010. It keeps on asking me for username and password and开发者_StackOverflow社区 does not seem to end.

I have tried to use "wsdl /server" command with same username & password, it generates a C# successfully.

How can I solve the problem? What is the alternative to adding a service reference?