How to create a GridView dynamically and show temporary data from Textboxes to GridView in ASP.Net

I am using

3 textboxes

1 dropdown

2 Buttons ( Add Row , Submit )

1 GridView ( For Temporary Data Holding of above controls )

Now what i want is that when a user fills some data in textboxes and select something from dropdown , then clicks on Add Row , this temporary gridview shows that data in it .... 

how to achieve it ?