URI formats not supported

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C#

Hi..
I kept my files in F drive and i want to export my folder through my localhost url. For that i gave in web.config file as

<add key="importUrl" value="http://localhost:2022/bin/TTI/Import"/>
        <add key="exportUrl" value="http://localhost:2022/bin/TTI/Export"/>

In my code,i gave as

string savePath = "~/Export";
using (WebClient client = new WebClient())
{
     var path = Server.MapPath("~/Export");
}
DirectoryInfo di = new DirectoryInfo(@"F:/VS2008/TTI_Script(Web)/TTI_Script(Web)/bin/TTI/Import");

Im getting error as "URI formats not supported in the above line...I tried but don't know how to solve this issue. Guide me.