<script>

function getUNCPath() {
 var filePath = document.getElementById("uploadedFile").value;

var WshNetwork = new ActiveXObject("WScript.Network"); 
 var Drives = WshNetwork.EnumNetworkDrives(); 
 for (i = 0; i < Drives.length; i += 2) {
 if(Drives.Item(i) != "")
 {
 if(filePath.match("^"+Drives.Item(i))){ 
 filePath = filePath.replace(Drives.Item(i), Drives.Item(i + 1)); 
 break;
 }
 }}
 }

</script>

<form onsubmit="getUNCPath()">
<input type="file" id="uploadedFile"/>
<input type="submit" value="Get the UNC Path!" />
</form>

in razor view engine add the following line to support ActiveXObject:

@using System.Web.Script.Serialization