file path of WebConfiguration

hi ,
 i want to change  my web.config file of one web site that it is put on localhost via application(c#) .
but in my program i write  following code:
System.Configuration.Configuration myConfiguration = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("C:\\Inetpub\\wwwroot\\Hesabdari\\web.config");
i give this error:
'C:\Inetpub\wwwroot\Hesabdari\web.config' is not a valid virtual path.
please say to me what can i do please..
thanks and best regards
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