OS : windows server 2003
DB : SQL server 2000

Would you help me?

case1

    string conn = "server=localhost; database=Dotnet; uid=sa; pwd=;";
    SqlConnection connection = new SqlConnection(conn);
    connection.Open();

This case1 is occurred Exception(System.InvalidCastException)

[InvalidCastException: ÁöÁ¤ÇÑ Ä³½ºÆ®°¡ À߸øµÇ¾ú½À´Ï´Ù.]
   ASP.control_test_aspx.Setmyname(Object src, EventArgs e) +133
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +108
   System.Web.UI.WebControls.Button.System.Web.UI.IPo stBackEventHandler.RaisePostBackEvent(String eventArgument) +57
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEve ntHandler sourceControl, String eventArgument) +18
   System.Web.UI.Page.RaisePostBackEvent(NameValueCol lection postData) +33
   System.Web.UI.Page.ProcessRequestMain() +1277



case2

    string conn = "server=localhost; database=Northwind; uid=sa; pwd=;";
    SqlConnection connection = new SqlConnection(conn);
    connection.Open();

This case2 is not occurred Exception. Login success.

Q1. I don't understand above state. Why case1 have CastExeption?

case3

    string conn = "server=localhost; database=Northwind; uid=Administrator; pwd=star_3327;";
    SqlConnection connection = new SqlConnection(conn);
    connection.Open();

This case3 can't login sql server(System.Data.SqlClient.SqlException).

[SqlException: 'Administrator' »ç¿ëÀÚ°¡ ·Î±×ÀÎÇÏÁö ¸øÇß½À´Ï´Ù.]
   System.Data.SqlClient.ConnectionPool.GetConnection (Boolean& isInTransaction) +472
   System.Data.SqlClient.SqlConnectionPoolManager.Get PooledConnection(SqlConnectionString options, Boolean& isInTransaction) +372
   System.Data.SqlClient.SqlConnection.Open() +384
   ASP.control_test_aspx.Setmyname(Object src, EventArgs e) +72
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +108
   System.Web.UI.WebControls.Button.System.Web.UI.IPo stBackEventHandler.RaisePostBackEvent(String eventArgument) +57
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEve ntHandler sourceControl, String eventArgument) +18
   System.Web.UI.Page.RaisePostBackEvent(NameValueCol lection postData) +33
   System.Web.UI.Page.ProcessRequestMain() +1277

Q2. Why case3 can't login?