How to create Gridview Hierarchy (Expandable Grids) or Child Grid into Parent Grid in .NET?

How to create Gridview Hierarchy (Expandable Grids) or Child Grid into Parent Grid in .NET?
 
Gridview is used to display data in a tabular form in ASP.NET and C#? To be more accurate Gridview is displays linear data. But sometimes you need to show hierarchy of data in the grid.
 
For example, you show parent records in each row of the grid and expanding each row displays child data. In this case you have to show a child grid under the parent row of the parent grid. You should be able to hide and show the child grid.
 
I had this requirement in one of my .NET project. I googled a lot and found some informative articles on telerik, codeproject and devexpress. I thought I should share it with you.

Expandable Grid Links
 
1. Telerik:
 
 
2. Codeproject
 
 
3. DevEx
 
 
Other Links