Setting Validation error template from code in WPF

Question

I have a TextBox in my WPF app. I have defined a ControlTemplate for validation error as follows:

Answer 1

For your first question. You can set the ErrorTemplate from code behind like.

    public MainWindow()
    {
        InitializeComponent();

        var template = this.FindResource("validationTemplate") as ControlTemplate;
        Validation.SetErrorTemplate(this.textBox1, template);
     }

Edit: For your second question. Please refer the following sample. sites.google.com/site/html5tutorials/ValidationErrorText.zip