private void btnOK_Click(object sender, EventArgs e)
        {
            bool isOk = true ;

            //Validate UserID
            if (string.IsNullOrWhiteSpace(this.txtUserID.Text))
            {
                this.errorProvider1.SetError(this.txtUserID, "請輸入帳號");
               isOk = false  ;
            }
            else
                this.errorProvider1.SetError(this.txtUserID, "");

            //Validate Password
            if (string.IsNullOrWhiteSpace(this.txtPassword.Text))
            {
                if (MessageBox.Show("確定密碼是空白嗎?","注意", MessageBoxButtons.YesNo, MessageBoxIcon.Information) != System.Windows.Forms.DialogResult.Yes) {
                    isOk = false ;
                }
            }

            if (isOk)
            {
                if (this.AfterInputCredential != null)
                {
                    EmailCredentialEventArgs arg = new EmailCredentialEventArgs(this.txtUserID.Text, this.txtPassword.Text, this.txtCC.Text);
                    this.AfterInputCredential(this, arg);
                }
                this.Close();
            }
        }
 void frmCred_AfterInputCredential(object sender, EmailCredentialEventArgs args)
 {
     this.SenderEmail = args.UserID;
     this.SenderPassword = args.Password;
     this.CC = args.CC;
 }