My Problem is to manage Hosting account programmatically using c# in ASP.Net:

1.  Creating sub-domains

2.  Managing FTP users

3.  Managing email accounts

4.  E-mail forwording

5.  E-mail listing

6.  Creating Databases like MySql, SQL, Postgre, MS Access, etc.

7.  Managing Ad-On domains

and more that can be posible 

Can anyone help me and give me the exact concept or any API free of cost which allow all these things

You're asking a lot for a simple forum post, lol. I don't believe there's any API out there that just allows you to do all of this. You may want to look into different hosting control panel software (Plesk, CPanel, etc). They've spent countless hours developing just what you're asking, I don't think anyone could possibly provide you with the information to replicate that in a forum post.

Check Microsoft's hosting resources for suggestions and control panels.  Remember that DNS, email and database management have nothing to do with IIS.

Jeff 

Search MSDN about WMI

Good Luck...

download dotnetpanel and use it is free for 1 server and 5 users

www.dotnetpanel.com

it is fast 

thanks for a nice solution, but I am developing my own API for this purpose, I am working on this and a lot of things I have fullfilled.

To do things like manage sub domains, creating domains, etc. control panels usually provide an API.

I have experience in PLESK panel. PLESK panel provides XML based interface for you to programatically achieve admin tasks.

You have to read the documentation for the control panel you are using - I am sure they offer this.

You also have to consult your hosting provider to see if they allow XML RPC remote calls. Mine didn't and I had to specifically ask them for this permission for a payment.

Remember, you wont be able to use IIS management classes available in .NET to manage IIS directly because of permissions. You would need to use API provided by the control panel.

Also if you are renting web space, looking into WMI (as suggested above) or ADSI or .NET managed classes would be useless.

If you have server admin access, however, you can look into following

Microsoft.Web.Administration which is very easy to use.

WMI

ADSI