Date format (dd/MM/yyyy) validation using Regular Expression in C# and VB.Net

Here Mudassar Ahmed Khan has explained with an example, how to perform Date format validation (dd/MM/yyyy) using Regular Expression in C# and VB.Net. The User will enter Date in TextBox and when the Button is clicked, the Date will be tested against the Regular Expression for dd/MM/yyyy format and if invalid, a Message Box will be displayed.