Validation groups allow you to organize validation controls on a page as a set.
        Each validation group can perform validation independently from other validation
        groups on the page. You create a validation group by setting the ValidationGroup
        property to the same name (a string) for all the controls you want to group. You
        can assign any name to a validation group, but you must use the same name for all
        members of the group.
    
    
        There are two validation groups in this example:
    
    
        - The "SelectionFormValidationGroup" contains two RadComboBox controls
            which are validated by CustomFieldValidator control. 
            The javascript method iterates through all RadComboBoxes DOM objects and validate their's value properties. 
            When DefaultItem is set it's value is set to the RadComboBox's DOM object value property.
        
- The "SearchFormValidationGroup" contains a RadTextBox and a 
            RadComboBox which are validated by two RequiredFieldValidator
            controls. The ValidationGroup property of the validators and the
            "Search" button is set to SearchFormValidationGroup. Pressing the "Search"
            button will trigger validation only for the SearchFormValidationGroup.