string strcmd;
                if (txtloginname.Text != "" && txtpassword.Text != "")
                {
                    strcmd = "select * from EmployeesCompetence where employeeid=" + txtloginname.Text + " and pwd='" + txtpassword.Text + "'";
                    login.Select(strcmd, "login");
                    if (sql.ds.Tables["login"].Rows.Count != 0)
                    {
                        Form mainfrm = new FrmMain();
                        mainfrm.Show();
                        this.Hide();
                    }
                    else
                        MessageBox.Show("用户名或密码错误！");
                }
这个是我做的登陆界面确定的代码，怎么在这里加上权限判断呢，先谢啦

版主可以加q么，我正在做一个课程设计，有很多东西不懂啊

。。。。。。。。在那段代码中加一个什么字段来判断权限呢

是在select语句中加入这张权限表，然后where语句查询这个权限的字段，判断在登陆界面选择的权限是否与这个表中的数据一致对么？

恩，谢谢版主啊，我搞下试试，不行的话我在问啊

版主在么，做完登录界面后，程序崩溃，显示数据库登录失败： public static  DataSet ds = new DataSet();
        public static string connstring = "server=.;database=ssxt;uid=sa;pwd=123456;";
        //执行select命令，并返回结果写入数据集的表中
        public bool  Select(string cmdstr, string tablename)
        {

               SqlConnection  conn = new SqlConnection(connstring);
                conn.Open();
                SqlCommand cmd = new SqlCommand(cmdstr, conn);
                cmd.ExecuteNonQuery();
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                sda.Fill(ds, tablename);
                conn.Close();
                return true;

        }
        public void Insert(string cmdstr)
        {
            SqlConnection conn = new SqlConnection(connstring);
            conn.Open();
            SqlCommand cmd = new SqlCommand(cmdstr, conn);
            cmd.ExecuteNonQuery();
            conn.Close();
        }
        public void Update(string cmdstr)
        {
            SqlConnection conn = new SqlConnection(connstring);
            conn.Open();
            SqlCommand cmd = new SqlCommand(cmdstr, conn);
            cmd.ExecuteNonQuery();
            conn.Close();
        }
        public void Delete(string cmdstr)
        {
            SqlConnection conn = new SqlConnection(connstring);
            conn.Open();
            SqlCommand cmd = new SqlCommand(cmdstr, conn);
            cmd.ExecuteNonQuery();
            conn.Close();
这个是我编写的类，运行后出现：  这个是我的按钮代码： sql login = new sql();
        private void button1_Click(object sender, EventArgs e)
        {
            string strcmd;
            if (txtloginname.Text != "" && txtpassword.Text != "")
            {
                strcmd = "select * from ygb where yg_id=" + txtloginname.Text + " and mm='" + txtpassword.Text + "'";
                login.Select(strcmd, "login");
                if (sql.ds.Tables["login"].Rows.Count != 0)
                {
                    Form GLYJM = new frmlogin();
                    GLYJM.Show();
                    this.Hide();
                }
                else
                    MessageBox.Show("用户名或密码错误！");
            }

就这个

未处理 System.Data.SqlClient.SqlException
  Message="无法打开登录所请求的数据库 \"ssxt\"。登录失败。\r\n用户 'sa' 登录失败。"
  Source=".Net SqlClient Data Provider"
  ErrorCode=-2146232060
  Class=11
  LineNumber=65536
  Number=4060
  Procedure=""
  Server="."
  State=1
  StackTrace:
       在 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
       在 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
       在 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
       在 System.Data.SqlClient.(Boolean enlistOK)
       在 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject)
       在 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart)
       在 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance)
       在 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance)
       在 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection)
       在 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options)
       在 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject)
       在 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject)
       在 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
       在 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
       在 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
       在 System.Data.SqlClient.SqlConnection.Open()
       在 WindowsFormsApplication1.sql.Select(String cmdstr, String tablename) 位置 E:\C#实训\c#实训界面设计\WindowsFormsApplication1\sql.cs:行号 20
       在 WindowsFormsApplication1.frmlogin.button1_Click(Object sender, EventArgs e) 位置 E:\C#实训\c#实训界面设计\WindowsFormsApplication1\frmlogin.cs:行号 26
       在 System.Windows.Forms.Control.OnClick(EventArgs e)
       在 System.Windows.Forms.Button.OnClick(EventArgs e)
       在 System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       在 System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       在 System.Windows.Forms.Control.WndProc(Message& m)
       在 System.Windows.Forms.ButtonBase.WndProc(Message& m)
       在 System.Windows.Forms.Button.WndProc(Message& m)
       在 System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       在 System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       在 System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       在 System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       在 System.Windows.Forms.(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       在 System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       在 System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       在 System.Windows.Forms.Application.Run(Form mainForm)
       在 WindowsFormsApplication1.Program.Main() 位置 E:\C#实训\c#实训界面设计\WindowsFormsApplication1\Program.cs:行号 18
       在 System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       在 System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       在 Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       在 System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       在 System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       在 System.Threading.ThreadHelper.ThreadStart()
  InnerException: 就这个