in some way these codes will help you very much if you need
to know file extension.
method below returns true if extension are any of the following -

it is possible to run Application.Run twice in csharp
application.the following example shows that.it's a
example to create login to access the application.

HttpCookie is a very good way to store small amount of data
in asp.net application/website.you can access cookie value in
any page once set in a page.cookie can stay for long time in the
user's computer.

In wordpress there are some definite ways to add scripts and styles
in your custom plugin.If you don't follow these rules you might
encounter numerous problems specially related with jquery.

if you are participating in a project of a
course,assignment,others on c#.net or asp.net
or may be others then you should follow the
steps for finishing the project successfully.