C# textBox validation

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" and fields are not filled..

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