Spurious pathname for ASP.Net graph - asp.net

Question

I'm generating a graph in an ASP.Net application. To this end I have included the chart control in the ASPX file like this:-
<asp:Chart ID="ourChart"
runat="server"
Height="500px"
width="520px"
BackColor="Black"
ImageLocation="~/GraphTempFiles/ChartPic_#SEQ(300,3)"
ImageStorageMode="UseImageLocation"
ImageType="Bmp">
and have added what I believe to be the requisite features to the web.config:-
<system.webServer>
<validation validateIntegratedModeConfiguration="false"/>
<modules runAllManagedModulesForAllRequests="true"/>
<handlers>
<add name="ChartImg"
verb="*" path="ChartImg.axd"
type="System.Web.UI.DataVisualization.Charting.ChartHttpHandler, System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
</handlers>
</system.webServer>
<appSettings>
<add key="ChartImageHandler"
value="storage=file;timeout=20;Url=~/GraphTempFiles;" />
</appSettings>
The result of all this is that the page displays with a server error in the application:-
Could not find a part of the path
'\MyDisk\MyDirectory\MyProgram\(S(32rdrd5zxhvc3rhq2szdxv2w))\GraphTempFiles\ChartPic_000001.bmp'.
Does anyone know what the matter is? (Presumably I am not supposed to create a directory (S(32rdrd5zxhvc3rhq2szdxv2w)) at any point; the number in the brackets varies each time I run it.)
I am using Visual Studio 2013 on Windows 8.1, with Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34248, as it says at the bottom of the page.

Answer 1

Most probably this error occurs since ASP.NET Cookieless Feature is enabled in web.config file like this:
<sessionState mode="InProc" cookieless="UseUri" timeout="60" />
According Understand How the ASP.NET Cookieless Feature Works to :
UseUri: The cookieless feature will always be used.
In that case Url may look like this: http://mysite/MyWebApp/(S(XXXX))/home.aspx
There are at least two options available to resolve it:
Option 1, disable Cookieless Feature, use, for example, default settings for sessionState element:
<sessionState mode="InProc" customProvider="DefaultSessionProvider">
<providers>
<add name="DefaultSessionProvider" type="System.Web.Providers.DefaultSessionStateProvider, System.Web.Providers, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" connectionStringName="DefaultConnection"/>
</providers>
</sessionState>
Option 2, specify the relative physical path for ImageLocation property of Chart control, for example:
<asp:Chart ID="ourChart"
runat="server"
Height="500px"
width="520px"
BackColor="Black"
ImageLocation="GraphTempFiles/ChartPic_#SEQ(300,3)"
ImageStorageMode="UseImageLocation"
ImageType="Bmp"/>