Validation groups allow you to assign validation controls on a page to a specific category. Each validation group can be validated independently from other validation groups on the page. Use the HtmlInputImage.ValidationGroup property to specify the name of the validation group for which the System.Web.UI.HtmlControls.HtmlInputImage control causes validation when it posts back to the server.

This property has an effect only when the value of the HtmlInputImage.CausesValidation property is set to true. When you specify a value for the HtmlInputImage.ValidationGroup property, only the validation controls that are part of the specified group are validated when the System.Web.UI.HtmlControls.HtmlInputImage control posts back to the server. If you do not specify a value for this property and the HtmlInputImage.CausesValidation property is set to true, all validation controls on the page that are not assigned to a validation group are validated when the control posts back to the server.