Get Selected Text and Value inside DropDownList SelectedIndexChanged event in ASP.Net

Here Mudassar Ahmed Khan has explained with an example, how to get the selected Text and Value of DropDownList inside SelectedIndexChanged event in ASP.Net using C# and VB.Net. Inside the SelectedIndexChanged event, the selected Text and Value of ASP.Net DropDownList will be displayed in JavaScript Alert Message Box using C# and VB.Net.