Life cycle of SPContext.ListItem

Question

I have created a messaging system (basically a simple announcement list with a recipient and a IsRead flag).

This have been done by creating the classics web fields, content type, list schema and list instance. All of this is working as expected.

I want to set the Isread flag (a boolean field) as soon as the user navigates to the dispform page.

In order to reach this goal, I've created a simple webpart with no UI that set the IsRead field on the SPContext.ListItem item :

[ToolboxItemAttribute(false)]
public class MessageSetRead : WebPart
{
    protected override void OnInit(EventArgs e)
    {
        try
        {

            var listItem = SPContext.Current.ListItem;

            // TODO: ensure listitem is a message and exists
            var isReadField = listItem.Fields.GetFieldByInternalName("IsRead");
            var isRead = (bool)listItem[isReadField.Id];
            var recipientField = listItem.Fields.GetFieldByInternalName("AssignedTo");
            var recipientStr = (string) listItem[recipientField.Id];

            var isCurrentUserRecipient =  string.IsNullOrEmpty(recipientStr) ?
                false: 
                new SPFieldUserValue(SPContext.Current.Web, recipientStr).LookupId == SPContext.Current.Web.CurrentUser.ID;


            if (!isRead && isCurrentUserRecipient)

                SPContextUtilities.RunWithElevatedPrivileges((elevatedSite, elevatedWeb) =>
                {
                    using (elevatedWeb.CreateUnsafeUpdateAllowedContext())
                    {
                        var elevatedList = elevatedWeb.Lists[SPContext.Current.ListId];
                        var elevatedListItem = elevatedList.Items.GetItemById(SPContext.Current.ItemId);
                        elevatedListItem[isReadField.Id] = true;
                        elevatedListItem.SystemUpdate(false);
                    }
                });
            }
        }
        catch (Exception exc)
        {
            this.Controls.Clear();
            var errorMessage = new Label();
            errorMessage.Text = HttpUtility.HtmlEncode(exc.ToString());
            errorMessage.Style[HtmlTextWriterStyle.WhiteSpace] = "no-wrap";
            errorMessage.Style[HtmlTextWriterStyle.Color] = "red";
            this.Controls.Add(errorMessage);
        }
    }
}

The webpart is put on the dispform.aspx file from the list schema.xml file :

      <Form Type="DisplayForm"
            Url="DispForm.aspx"
            SetupPath="pages\form.aspx"
            WebPartZoneID="Main">
        <WebParts>
          <AllUsersWebPart WebPartOrder="Integer"
                           WebPartZoneID="Main">
            <![CDATA[
            <webParts>
  <webPart xmlns="http://schemas.microsoft.com/WebPart/v3">
    <metaData>
      <type name="MyCustomer.Messaging.MessageSetRead.MessageSetRead,    $SharePoint.Project.AssemblyFullName$" />
      <importErrorMessage>$Resources:core,ImportErrorMessage;</importErrorMessage>
    </metaData>
    <data>
      <properties>
        <property name="Title" type="string">MessageSetRead</property>
        <property name="Description" type="string">My WebPart</property>
      </properties>
    </data>
  </webPart>
</webParts>

            ]]>
          </AllUsersWebPart>
        </WebParts>
      </Form>

Everything is working but with one gotcha.

When I navigate to the dispform, the IsRead flag is actually set to true, but the user see 'No' in the item. A simple refresh will show the 'Yes' value as expected.

I think this is due to the SPContext.ListItem population which occurs before my Page_Init.

What is the life cycle of the SPContext.ListItem object ?

How should I change my code to see the updated value of my field ?

Thanks

PS: using SP 2010 Enterprise

Answer 1

I would solve this client side (with Client Object Model) instead. You could either insert a content query / forms web part with some javascript code that sets the property, or use CustomAction in Ribbon or even a delegate control to add a script to additionalPageHead that checks for what list is present and act accordingly.

I dont have any code sample present, but it should be pretty straight forward.

Answer 2

Why do you want to show a field in DisplayForm if it is always True? :)

I would suggest setting SPField.ShowInDisplayForm to false for this field, and you're basically done. It will not be shown in the display form after this, but will appear everywhere else.

And I want to warn you about content editor and javascript approach: using JS hacks to set a value to a field is actually a fragile tactics. Most JS/jQuery hacks use field Title to retrieve the field control, and field titles could be easily changed by a portal user, without even noticing that he actually broke your functionality...

If you still want users to see this always-true-field in your display form, why, you can create another Calculated field, which always evaluates to True, and show it instead :)