private void SimpleLoginButton_Click(object sender, RoutedEventArgs e) { LoginTextBox.ClearValue(TextBox.BorderBrushProperty); LoginTextBox.ClearValue(TextBox.PlaceholderTextProperty); if (string.IsNullOrWhiteSpace(LoginTextBox.Text)) { LoginTextBox.BorderBrush = new SolidColorBrush(Colors.Red); LoginTextBox.PlaceholderText = "Login is required"; } else if (LoginTextBox.Text.Length <= 3) { LoginTextBox.BorderBrush = new SolidColorBrush(Colors.Red); } }