c# - 当我输入第一个字符时，C#-确认，密码和电子邮件文本框显示我消息框

Question

 //code for confirm password text box:

     private void txtRegPassConfirm_TextChanged_1(object sender, EventArgs e)
            {
                    if (txtRegPassConfirm.Text != txtRegPass.Text)
                    {
                        MessageBox.Show("Passwords do not match");
                        txtRegPassConfirm.Clear();
                    }

                    else
                    {
                        MessageBox.Show("textbox can not be empty");   
                    } 
                }


    //code for text box Password:

     private void txtRegPass_TextChanged(object sender, EventArgs e)
            {

                if (txtRegPass.Text.Length < 8)
                {

                    MessageBox.Show("Password must be at least 8 characters long");
                    txtRegPassConfirm.Clear();
                }


  // code for text box Email:

     private void txtRegEmail_TextChanged_1(object sender, EventArgs e)
        {


            string c = ConfigurationManager.ConnectionStrings["Constr"].ConnectionString;
            SqlConnection con = new SqlConnection(c);
            con.Open();
            SqlCommand cmd = new SqlCommand("EmailReg", con);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@Email", this.txtRegEmail.Text);
            SqlDataReader dr = cmd.ExecuteReader();
            while (dr.Read())
            {
                if (dr.HasRows == true)
                {
                    MessageBox.Show("Email = " + dr[4].ToString() + "is Already exist");
                    txtRegEmail.Clear();
                    break;
               }
                Regex r = new Regex("^[a-zA-Z0-9){1,20}@[a-zA-Z0-9){1,20}.[a-zA-Z]{2,3}$");

                if (!r.IsMatch(txtRegEmail.Text))
                {
                    txtRegEmail.Clear();
                    MessageBox.Show("incorrect formate");
                }

            }

        }

//code for button Registration:

private void btnRegistration_Click_1(object sender, EventArgs e)
        {

                string c = ConfigurationManager.ConnectionStrings["Constr"].ConnectionString;
                SqlConnection con = new SqlConnection(c);
                con.Open();
                SqlCommand cmd = new SqlCommand("RegistrationForm", con);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@UserName", txtRegUserN.Text);
                cmd.Parameters.AddWithValue("@Password", txtRegPass.Text);
                cmd.Parameters.AddWithValue("@Confirm", txtRegPassConfirm.Text);
                cmd.Parameters.AddWithValue("@Email", txtRegEmail.Text);
                SqlDataReader dr = cmd.ExecuteReader();

                while (dr.Read())
                {
                    if (dr.HasRows == true)
                    {
                        MessageBox.Show("Data Inserted Succesfully");

                    }
                }

              if (dr.HasRows == false)
               {

                  MessageBox.Show("Access Denied, enter the correct fields");
               }

              else
              {
                  MessageBox.Show("Enter correct info");
              }
       }

当我执行该应用程序并在确认文本框中输入密码时，它会向我显示输入第一个字符“密码不匹配”的消息框。以及在“密码”文本框中显示“密码必须至少8个字符长”的消息。就像在“电子邮件”文本框中一样，我要应用正则表达式但不起作用。我将代码移到了电子邮件部分，但是它显示了“电子邮件无效”正则表达式消息框。现在，告诉我输入不匹配字（而不是输入第一个字符）时如何获得消息框。

Answer 1

主要问题：

您正在检查文本框TextChanged事件中的验证规则。下面列出了一些可以帮助您执行验证的选项：

选项1：在按钮的单击事件中验证

您可以在注册按钮的Click事件中检查验证，例如：

private void registerButton_Click(object sender, EventArgs e)
{
    //Check for password length           
    if (txtRegPass.Text.Length < 8)
    {
        MessageBox.Show("Password must be at least 8 characters long");
        txtRegPass.Focus();
        return;
    }

    //Check for other validations
    //...
    // don't forget to return; if the state is not valid


    //If the code execution reaches here, it means all validation have been passed
    //So you can save data here.
}

选项2：使用验证事件和ErrorProvider

作为更好的解决方案，可以使用 ErrorProvider。将错误提供程序放在窗体中并处理TextBoxes的 Validatin事件，然后为该控件设置错误。

然后在您的注册按钮的Click事件中，您可以检查是否存在任何验证错误。

这是屏幕截图：

private void ValidationTest_Load(object sender, EventArgs e)
{
    this.AutoValidate = System.Windows.Forms.AutoValidate.EnableAllowFocusChange;
}

private void passwordTextBox_Validating(object sender, CancelEventArgs e)
{
    if (this.passwordTextBox.TextLength < 8)
    {
        this.errorProvider1.SetError(this.passwordTextBox, "Password must be at least 8 character");
        e.Cancel = true;
    }
    else
    {
        this.errorProvider1.SetError(this.passwordTextBox, "");
    }
}

private void confirmTextBox_Validating(object sender, CancelEventArgs e)
{
    if (this.confirmTextBox.Text != this.passwordTextBox.Text)
    {
        this.errorProvider1.SetError(this.confirmTextBox, "Password and Confirm must be the same");
        e.Cancel = true;
    }
    else
    {
        this.errorProvider1.SetError(this.confirmTextBox, "");
    }
}

private void registerButton_Click(object sender, EventArgs e)
{
    if (this.ValidateChildren())
    {
        //Do registration here
    }
    else
    {
        var listOfErrors = this.errorProvider1.ContainerControl.Controls
                            .Cast<Control>()
                            .Select(c => this.errorProvider1.GetError(c))
                            .Where(s => !string.IsNullOrEmpty(s))
                            .ToList();
        MessageBox.Show("please correct validation errors:\n - " +
            string.Join("\n - ", listOfErrors.ToArray()),
            "Error",  
            MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}