The client-side Invalid property for RadInput controls was introduced in Q2 2013. This property could be used to get or set the state of a control from the RadInput group on the client. It is a client-side property and its value is not persisted on the server. Also the server-side Invalid property is not affected by it. However if you set the server-side Invalid property to true, the client-side property will also be set to true.
In order to set a RadInput control as invalid on the server you could use the following line:
After the property is set to true a Css class called .riError will be applied to the control.
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