引用 如何用C#寫一個簡單的Login視窗

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 如何用C#寫一個簡單的Login視窗

最近，看到網上經常會問如何進行視窗跳轉，大多數的問題都是牽扯到Login視窗。其實，在Visual Studio 6以來，比較正確的做法，是判斷Login視窗的傳回值，然後決定是否開啟主表單，那麼在C#中也是一樣的。

 

具體做法如下：

首先，建立Login視窗，然後添加相應的輸入框和按鈕，設定視窗的AcceptButton為表單的確認按鈕，而CancelButton為表單的取消按鈕。例如：

            this.AcceptButton = this.btnOK;

            this.CancelButton = this.btnCancel;

 

定義確定按鈕以及取消按鈕事件，如下：

        private void btnOK_Click(object sender, System.EventArgs e)

        {

            // Here is to use fixed username and password

            // You can check username and password from DB

            if( txtUserName.Text == "Admin" && txtPassword.Text == "nopassword" )

            {

                // Save login user info

                uiLogin.UserName = txtUserName.Text;

                uiLogin.Password = txtPassword.Text;

 

                // Set dialog result with OK

                this.DialogResult = DialogResult.OK;

            }

            else

            {

                // Wrong username or password

                nLoginCount++;

                if( nLoginCount == MAX_LOGIN_COUNT )

                    // Over 3 times

                    this.DialogResult = DialogResult.Cancel;

                else

                {

                    MessageBox.Show( "Invalid user name and password!" );

                    txtUserName.Focus();

                }

            }

        }

 

        private void btnCancel_Click(object sender, System.EventArgs e)

        {

            // Set dialog result with Cancel

            this.DialogResult = DialogResult.Cancel;

        }

 

然後，在Login表單的Closing事件中，要進行處理，如下：

private void frmLogin_Closing(object sender, System.ComponentModel.CancelEventArgs e)

{

    // Check whether form is closed with dialog result

    if( this.DialogResult != DialogResult.Cancel &&

        this.DialogResult != DialogResult.OK )

        e.Cancel = true;

}

 

除此外，Login表單一些輔助代碼如下：

        private int nLoginCount = 0;

        private const int MAX_LOGIN_COUNT = 3;

 

        private UserInfo uiLogin;

        public frmLogin( ref UserInfo ui )

        {

            //

            // Required for Windows Form Designer support

            //

            InitializeComponent();

 

            // Set login info to class member

            uiLogin = ui;

        }

 

       調用的時候，要修改程式的Main函數，如下：

        /// <summary>

        /// The main entry point for the application.

        /// </summary>

        [STAThread]

        static voidMain()

        {

            UserInfo ui = new UserInfo();

            frmLogin myLogin = new frmLogin( ref ui );

            if( myLogin.ShowDialog() == DialogResult.OK )

            {

                //Open your main form here

                MessageBox.Show( "Logged in successfully!" );

            }

            else

            {

                MessageBox.Show( "Failed to logged in!" );

            }

        }

 

       而附加的UserInfo類如下：

    /// <summary>

    /// User info class

    /// </summary>

    public class UserInfo

    {

        private string strUserName;

        private string strPassword;

        public string UserName

        {

            get{ return strUserName;}

            set{ strUserName = value;   }

        }

        public string Password

        {

            get{ return strPassword;}

            set{ strPassword = value;}

        }

        public UserInfo()

        {

            strUserName = "";

            strPassword = "";

        }

    }

 

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