create failed for database 'test'

See more:

C#

I try to create data base in c#(win app) by SMO.
My Code run correctly before,but it get erro now.

string serverStr=ConfigurationManager.AppSettings["Server"];
ServerConnection con=new ServerConnection(serverStr);

Server srv=new Server(Con);

Microsoft.SqlServer.Management.Smo.DataBase newDB=new Microsoft.SqlServer.Management.Smo.DataBase(srv,'test');

newDB.Create();

this is the error: create failed for database 'test'