Steps to implement DataTemplateSelector in ContentControl.
1. Create a class that inherits DataTemplateSelector.

2. Implement method SelectTemplate.
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
code here
}
3. In your XAML under resource, declare all data templates you wish to as example below.

4. Initialize your datatemplate selector class in reference to step number 1.

5. Under ContentControl: