private void ValidateRequiredFields(TextBox txtUsername, PasswordBox txtPassword, TextBox txtFirstName, TextBox txtLastName, out bool Validated)
{
Validated = false;
if(txtUsername.Text.IsNullOrEmpty()){
txtUsername.FlagAsError();
return;
} txtUsername.FlagAsCorrect();
if (txtPassword.Password.IsNullOrEmpty()) {
txtPassword.FlagAsError();
return;
} txtPassword.FlagAsCorrect();
if (txtFirstName.Text.IsNullOrEmpty()) {
txtFirstName.FlagAsError();
return;
} txtFirstName.FlagAsCorrect();
if (txtLastName.Text.IsNullOrEmpty()) {
txtLastName.FlagAsError();
return;
} txtLastName.FlagAsCorrect();
Validated = true;
}