Passing LinqDataSource through Session: 'DataContext accessed after Dispose.'

Question

I´m in need to pass some results from the database around. Instead of pass a whole dataset, or a constructed sql query, I tried to pass a LinqDataSource configured object.

On the source page, I configure the LinqDataSource object properties Where and WhereParameters using the values set by the user on the controls displayed on the page (search box, combo box etc.). I pass the object around to avoid the LinqDataSource reconfiguration on the receiver page.

But, even while it worked fine on my developing system, after deploying it on a dedicated server I got an error saying the following:

Cannot access a disposed object.

Object name: 'DataContext accessed after Dispose.'.

On both pages, the source and the receiver, the LinqDataSource objects are declared as:

<asp:LinqDataSource ID="myLinqDS" runat="server" 
    ContextTypeName="MyProject.MyDBNamedpace.MyDataContext" 
    TableName="TheTable"
    OrderBy="field1, field2"
</asp:LinqDataSource>

To pass the datasource object around I do this:

SetLinqDataSourceWhereAndHisParameters(); //just set Where and WhereParameters
Guid guid = Guid.NewGuid();
Session[guid.ToString()] = myLinqDS;
ScriptManager.RegisterStartupScript(this.Page,
    typeof(Page),
    "Redirect",
    String.Format(@"window.open(""{0}"");",
        this.ResolveClientUrl("~/PageToDisplayTheData.aspx?guid=" +
        System.Web.HttpUtility.UrlEncode(guid.ToString())
    ),
true);

And to retrieve, on PageToDisplayTheData.aspx´s codebehind:

myLinqDS =
   (LinqDataSource)Session[System.Web.HttpUtility.UrlDecode(Request.QueryString[guid])];
aDataList.DataSource = myLinqDS;
aDataList.DataBind();

Answer 1

You should not be storing the DataContext in Session (or anywhere) for the following reasons:

• The DataContext isn't thread safe
• The DataContext is designed as a Unit-Of-Work tool

If you query a collection within the DataContext it is internally cached, so when you requery it you don't do a round-trip to the database. But this can lead to data stagnation as the values don't reflect what the actual state of the underlying database.