AJAX Resizable extender control allows you to stretch and change the size of the target control. You can attach the resizable handle at the bottom right of the target control that will allow the user to resize the size of the control. AJAX Resizable control properties can be used to fix the maximum and minimum stretchable width and height of the target control. Resizable control consists of onClientResize, onClientResizeBegin and onClientResizing events that allow you to perform the action such as resizing the font size after resizing the control.
Properties of AJAX Resizable Control
You can learn the use of above properties and get the C# code from the tutorial of AJAX Resizable control by following the link provided at the bottom of this sample.
Try the sample below to understand the functionality of AJAX Resizable control: