Show Hide TextBox based on DropDownList selection in ASP.Net

Here Mudassar Ahmed Khan has explained with an example, how to show and hide TextBox based on DropDownList selection in ASP.Net using C# and VB.Net. When the YES item (option) is selected in the DropDownList, TextBox will be visible else the TextBox will be hidden in ASP.Net using C# and VB.Net.