AJAX :: Ajax Cascading Dropdown Control Not Working On IIS After Deploying?

I am new to Ajax Control Toolkit, with the help of online tutorials I had created a cascading dropdown list in asp.net and tested it on my local machine. For this dropdown list data source would be an xml file (which is saved on my local machine c drive). I haven't encountered any issues until I deploy the precompiled web site on to IIS 7. When I open the web site from IIS I would see the two dropdown boxes on the web page with an error "Method error 500". I believe this error occured due to incorrect xml file
path provided on IIS. I had copied xml and xsd files into IIS server C drive but it did not help out and then I created a network map and placed the xml and xsd files in that shared folder tried to access that path from web service, it's working on local machine but not on IIS. It would be great, if any one could explain me the solution.

Following is the .aspx and .asmx code:

.aspx code:

<form id="form1" runat="server"> <div> <asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server"> </asp:ToolkitScriptManager> <br /> <table> <tr> <td> <asp:DropDownList ID="DropDownList1" runat="server"
Height="20px" Width="257px"> </asp:DropDownList> <asp:CascadingDropDown ID="CascadingDropDown1" runat="server" Category="Category" TargetControlID="DropDownList1" PromptText="[select category]" ServicePath="~/WebService.asmx" ServiceMethod="GetCategory"> </asp:CascadingDropDown>
<br /> </td> </tr> <tr> <td> <asp:DropDownList ID="DropDownList2" runat="server" Height="20px" Width="257px"> </asp:DropDownList> <asp:CascadingDropDown ID="CascadingDropDown2" runat="server" Category="Type" TargetControlID="DropDownList2" PromptText="Select
Type]" LoadingText="Loading Type.." ParentControlID="DropDownList1" ServicePath="~/WebService.asmx" ServiceMethod="GetType"> </asp:CascadingDropDown> <br /> </td> </tr> </table> </div> </form>

.asmx code(.cs code):

[WebMethod]
public AjaxControlToolkit.CascadingDropDownNameValue[] GetCategory(string knownCategoryValues, string category)
{
XmlDocument _doc = new XmlDocument();
_doc.Load(HttpContext.Current.Server.MapPath("~/C:/ItSupportCategory.xml"));
XmlNodeList list = _doc.SelectNodes("/CategoryList/Category");
List<CascadingDropDownNameValue> categorylist = new List<CascadingDropDownNameValue>();
foreach (XmlNode node in list)
{
string catid = node.Attributes["value"].Value.ToString();
string catname = node.Attributes["name"].Value.ToString();
categorylist.Add( new CascadingDropDownNameValue(catname,catid));
}
return categorylist.ToArray();
}
[WebMethod]
public AjaxControlToolkit.CascadingDropDownNameValue[] GetType(string knownCategoryValues, string category)
{
int catID;
StringDictionary selectedvalue = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
catID = Convert.ToInt32(selectedvalue["category"]);
List<AjaxControlToolkit.CascadingDropDownNameValue> cascadingValues = new List<AjaxControlToolkit.CascadingDropDownNameValue>();
XmlDocument _doc = new XmlDocument();
_doc.Load(HttpContext.Current.Server.MapPath("~/C:/ItSupportCategory.xml"));
XmlElement root = (XmlElement)_doc.SelectSingleNode("/CategoryList/Category[@value='" + catID + "']");
for (int i = 0; i < root.ChildNodes.Count; i++)
{
string typeid = root.ChildNodes[i].Attributes["value"].Value.ToString();
string typename = root.ChildNodes[i].Attributes["name"].Value.ToString();
cascadingValues.Add(new CascadingDropDownNameValue(typename, typeid));
}
return cascadingValues.ToArray();
}
Xml File:
<?xml version="1.0"?>
<CategoryList xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="test.xsd">
<Category value ="1" name="SYSTEM WIDE">
<Type value ="1" name="Email"/>
<Type value="2" name="SAP Locked"/>
<Type value="3" name="Job Archive Full" />
</Category>
<Category value="2" name="SAP">
<Type value="3" name="Pricing Incorrect"/>
<Type value="5" name="New Item #"/>
<Type value="6" name="Reports"/>
<Type value="7" name="New User Setup"/>
</Category>
<Category value="3" name="OTHER">
<Type value="8" name="Production"/>
<Type value="9" name="Office"/>
<Type value="10" name="Toner for Printer"/>
<Type value="11" name="Security Camre Lookup"/>
</Category>
</CategoryList>