AddDataTemplate method for WPFViewModelResolver class.

WPFViewModelResolver.AddDataTemplate.cs

private void AddDataTemplate(Type viewType, Type viewModelType)
{
    DataTemplate dataTemplate = this.CreateTemplate(viewType, viewModelType);

    if (!Application.Current.Resources.Contains(dataTemplate.DataTemplateKey))
    {
        Application.Current.Resources.Add(dataTemplate.DataTemplateKey, dataTemplate);
    }
    else
    {
        Console.WriteLine("Duplicated resource key: " + dataTemplate.DataTemplateKey.ToString());
    }
}