SqlConnection cnn = null;
        SqlCommand cmd = null;
        SqlDataAdapter sda = null;
        DataTable Dt = new DataTable();

        cnn = new SqlConnection("Server=dbadmin01.database.windows.net;Database=dbadmin;User=info;Password=notGivingThis");
        cmd = new SqlCommand("SELECT username FROM users WHERE username =@TextboxValue", cnn);
        cnn.Open();
        cmd.CommandType = CommandType.Text;
        cmd.Parameters.Add("@TextboxValue", SqlDbType.VarChar).Value = txtUser.Text;
        sda = new SqlDataAdapter(cmd);
        sda.Fill(Dt);

        if (Dt.Rows.Count > 0)
        {
            //Works - do nothing for now
        }
        else
        {
            MessageBox.Show("Username is incorrect!", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
        }

        cnn = new SqlConnection("Server=dbadmin01.database.windows.net;Database=dbadmin;User=info;Password=notGivingThis");
        cmd = new SqlCommand("SELECT passcode FROM users WHERE passcode =@PasswordValue", cnn);
        cnn.Open();
        cmd.CommandType = CommandType.Text;
        cmd.Parameters.Add("@PasswordValue", SqlDbType.VarChar).Value = pwdPassword.Password;
        sda = new SqlDataAdapter(cmd);
        sda.Fill(Dt);

        if (Dt.Rows.Count > 0)
        {
            //Works - Do nothing for now
        }
        else
        {
            MessageBox.Show("Password is incorrect!", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
        }

SELECT username FROM users WHERE username =@TextboxValue AND passcode =@PasswordValue

cmd = new SqlCommand("select Username,passcode from users where username =@username",cnn);

if (Dt.Rows[0]["passcode"].ToString()!=pwdPassword.Password)
{
    MessageBox.Show("Invalid Password");
    return;
}