C# textBox validation

Question

As I just started with C# I have some trouble to get started. I am trying to make a simple login system, and this is what I've got so far:

private void button1_Click(object sender, EventArgs e)
{
    string username = "Admin";
    string password = "root";

    if (!string.IsNullOrEmpty(textBox1.Text) && (!string.IsNullOrEmpty(textBox2.Text)))
        MessageBox.Show("Fields are not filled");

    if (!string.IsNullOrEmpty(textBox1.Text))
        MessageBox.Show("No Password inserted");

    if (!string.IsNullOrEmpty(textBox2.Text))
        MessageBox.Show("No username inserted");

    if ((textBox1.Text == username) && (textBox2.Text == password))
        MessageBox.Show("Login Succeed");
    else
        MessageBox.Show("Login failed");
}

When I type in Admin as username and root as password it gives me login succeed, when I do random Username & Password it gives me Login failed, that part works flawless. It's more about the "not inserted" part and when fields are not filled.

It simply does nothing :') It keeps saying "login failed" any idea how to fix this?

Answer 1

replace

!string.IsNullOrEmpty()

with

string.IsNullOrWhiteSpace()

so the complete solution:

private void button1_Click(object sender, EventArgs e)
{
    string username = "Admin";
    string password = "root";

    if (string.IsNullOrWhiteSpace (textBox1.Text))
        MessageBox.Show("No Password inserted");
    else if (string.IsNullOrWhiteSpace (textBox2.Text))
        MessageBox.Show("No username inserted");
    else if ((textBox1.Text == username) && (textBox2.Text == password))
        MessageBox.Show("Login Succeed");
    else
        MessageBox.Show("Login failed");

}

Answer 2

Try following:

private void button1_Click(object sender, EventArgs e)
        {
            string username = "Admin";
            string password = "root";

            //When both are empty
            if (string.IsNullOrEmpty(textBox1.Text) && string.IsNullOrEmpty(textBox2.Text))
            {
                MessageBox.Show("Fields are not filled");
                return;
            }

            //When username is empty    
            if (string.IsNullOrEmpty(textBox1.Text))
            {
                MessageBox.Show("No username inserted");
                return;
            }

            //When password is empty
            if (string.IsNullOrEmpty(textBox2.Text))
            {
                MessageBox.Show("No password inserted");
                return;
            }

            if ((textBox1.Text == username) && (textBox2.Text == password))
                MessageBox.Show("Login Succeed");
            else
                MessageBox.Show("Login failed");

        }

Answer 3

Main issue is the logic in first IF statement you're asking basically:

IF(Not-IsNullOrEmpty(LOGIN) AND Not-IsNullOrEmpty(PASS))
    SHOW MESSAGE

which is why it does not work.

I would probably rewrite it bit to not repeat myself and make it a bit more readable:

private void button1_Click(object sender, EventArgs e)
{
    string username = "Admin";
    string password = "root";
    var message = string.Empty;
    bool loginEmpty = string.IsNullOrEmpty(textBox1.Text),
         passEmpty = string.IsNullOrEmpty(textBox2.Text),
         loggedIn = (textBox1.Text == username) && (textBox2.Text == password);

    if (!loggedIn) 
    {
        if (loginEmpty && passEmpty)
            message = " - Fields are not filled";
        else if (passEmpty)
            message = " - No Password inserted";
        else if (loginEmpty)
            message = " - No username inserted";

        MessageBox.Show("Login failed" + message);
        return;
    }

    MessageBox.Show("Login succeded");
}