How to recheck field A from field B by using TextChanged?

Question

I am having a little problem here. Here is my situation:

I am typing user name: tester (valid user name; avoiding all checks) and then type password: testerr (valid password; avoiding all checks). Problem is that I am checking for the same inputs. And in my code when both inputs are the same I will see a notification. Now, when I type tester as user name and password I get the error, but when I add additional character to my password 'testerr' I am making password valid, but user name is checked as invalid saying that both are still the same and making my validation impossible.

How can avoid this? I was thinking of rechecking user name field from field 2, but I'm not sure how.

bool passIsValid, userIsValid;

public AuthenticationWindow()
{
    InitializeComponent();

    // Creating TextChanged events which till validate input fields.
    txtUserName.TextChanged += new EventHandler(txtUserName_TextChanged);
    txtPassword.TextChanged += new EventHandler(txtPassword_TextChanged);
}

private void txtUserName_TextChanged(object sender, EventArgs e)
{
    // Checking for empty user name field.
    if (string.IsNullOrEmpty(txtUserName.Text))
    {
        lblMessageUser.Text = "User Name field cannot be empty!";
        lblMessageUser.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
    }
    // Making sure that user name is at least 6 characters long.
    else if (txtUserName.Text.Length < 6)
    {
        lblMessageUser.Text = "User Name field must be at least 6 characters long!";
        lblMessageUser.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
    }
    // Checking for user name made of same repeating character.
    // Invalid example: 'aaaaaa'
    else if (!txtUserName.Text.Distinct().Skip(1).Any())
    {
        lblMessageUser.Text = "User Name cannot be made of repeating the same characters!";
        lblMessageUser.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
    }
    // Making sure that password and user name aren't the same.
    else if (txtUserName.Text == txtPassword.Text)
    {
        lblMessageUser.Text = "User Name and Password can not be the same!";
        lblMessagePass.Text = "User Name and Password can not be the same!";
        lblMessageUser.ForeColor = Color.IndianRed;
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
        passIsValid = false;
    }
    // If all other checks aren't trigered; enable authentication.
    else
    {
        lblMessageUser.Text = "User Name is valid.";
        lblMessageUser.ForeColor = Color.Green;

        userIsValid = true;

        if (passIsValid && userIsValid)
        {
            btnAuthenticate.Enabled = true;
        }
    }
}

private void txtPassword_TextChanged(object sender, EventArgs e)
{
    // Checking for Null or Empty string in password field.
    if (string.IsNullOrEmpty(txtPassword.Text))
    {
        lblMessagePass.Text = "Password field cannot be empty!";
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        passIsValid = false;
    }
    // Making sure that password is at least 6 characters long.
    else if (txtPassword.Text.Length < 6)
    {
        lblMessagePass.Text = "Password field must be at least 6 characters long!";
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        passIsValid = false;
    }
    // Checking for password made of same repeating character.
    // Invalid example: 'aaaaaa'
    else if (!txtPassword.Text.Distinct().Skip(1).Any())
    {
        lblMessagePass.Text = "Password cannot be made of repeating the same characters!";
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        passIsValid = false;
    }
    // Making sure that user name and password are not the same.
    // Security measure.
    else if (txtUserName.Text == txtPassword.Text)
    {
        lblMessageUser.Text = "User Name and Password can not be the same!";
        lblMessagePass.Text = "User Name and Password can not be the same!";
        lblMessageUser.ForeColor = Color.IndianRed;
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
        passIsValid = false;
    }
    // If all other checks aren't trigered; enable authentication.
    else
    {
        lblMessagePass.Text = "Password is valid.";
        lblMessagePass.ForeColor = Color.Green;

        passIsValid = true;

        if (passIsValid && userIsValid)
        {
            btnAuthenticate.Enabled = true;
        }
    }
}

Answer 1

You can merge your both events into one, then the user sees all errors and your check could be successful.

bool passIsValid, userIsValid;

public AuthenticationWindow()
{
    InitializeComponent();

    // Creating TextChanged events which till validate input fields.
    txtUserName.TextChanged += new EventHandler(txtCheck_TextChanged);
    txtPassword.TextChanged += new EventHandler(txtCheck_TextChanged);
}

private void txtCheck_TextChanged(object sender, EventArgs e)
{
    // Checking for empty user name field.
    if (string.IsNullOrEmpty(txtUserName.Text))
    {
        lblMessageUser.Text = "User Name field cannot be empty!";
        lblMessageUser.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
    }
    // Making sure that user name is at least 6 characters long.
    else if (txtUserName.Text.Length < 6)
    {
        lblMessageUser.Text = "User Name field must be at least 6 characters long!";
        lblMessageUser.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
    }
    // Checking for user name made of same repeating character.
    // Invalid example: 'aaaaaa'
    else if (!txtUserName.Text.Distinct().Skip(1).Any())
    {
        lblMessageUser.Text = "User Name cannot be made of repeating the same characters!";
        lblMessageUser.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
    }
    else
    {
        userIsValid = true;
        lblMessageUser.Text = "Password is valid.";
        lblMessageUser.ForeColor = Color.Green;
    }

    // Checking for Null or Empty string in password field.
    if (string.IsNullOrEmpty(txtPassword.Text))
    {
        lblMessagePass.Text = "Password field cannot be empty!";
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        passIsValid = false;
    }
    // Making sure that password is at least 6 characters long.
    else if (txtPassword.Text.Length < 6)
    {
        lblMessagePass.Text = "Password field must be at least 6 characters long!";
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        passIsValid = false;
    }
    // Checking for password made of same repeating character.
    // Invalid example: 'aaaaaa'
    else if (!txtPassword.Text.Distinct().Skip(1).Any())
    {
        lblMessagePass.Text = "Password cannot be made of repeating the same characters!";
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        passIsValid = false;
    }
    else
    {
        passIsValid = true;
        lblMessagePass.Text = "Password is valid.";
        lblMessagePass.ForeColor = Color.Green;
    }

    // Making sure that user name and password are not the same.
    // Security measure.
    if (txtUserName.Text == txtPassword.Text)
    {
        lblMessageUser.Text = "User Name and Password can not be the same!";
        lblMessagePass.Text = "User Name and Password can not be the same!";
        lblMessageUser.ForeColor = Color.IndianRed;
        lblMessagePass.ForeColor = Color.IndianRed;
        btnAuthenticate.Enabled = false;
        userIsValid = false;
        passIsValid = false;
    }

    // If all other checks aren't trigered; enable authentication.
    if (passIsValid && userIsValid)
    {
        btnAuthenticate.Enabled = true;
    }
}