Program.cs檔案新增如下內容

            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            //Application.Run(new Login());
            Login login = new Login();
 
            //介面轉換
            login.ShowDialog();
 
            if (login.DialogResult == DialogResult.OK)
            {
                login.Dispose();
                Application.Run(
 
new MainForm());
            }
            else if (login.DialogResult == DialogResult.Cancel)
            {
                login.Dispose();
                return;
            }

在登陸介面新增如下內容

//跳轉主介面
     this.DialogResult = DialogResult.OK;
     this.Dispose();
     this.Close();