Amar Galla’s Weblog

One of my colleagues asked me how to replace the title field in a SharePoint list with his own field and get the standard dropdown on that field. From my experience I have found that the title and id fields are very tightly intervoven with the SharePoint lists. It is easier to just change the display name of the Title field to whatever suits your needs.

If you open the standard schema.xml for any list, you will not find any definition for the title field. But still all lists contain that field. This definition comes from the onet.xml. It is not advisable to modify the onet.xml. However it is possible to modify the base field properties by simply overriding them in your schema.xml file. Just copy the definition, paste it in the fields section of your schema.xml, change the DisplayName to what you like, and add an attribute FromBaseType=”TRUE”. This will allow you to modify the way the base types work from your schema.xml.

Update: The title field actually displayed on the all items view is a calculated field called LinkTitle. This field is tied to the dropdown menu when you hover over the Title.

I recently ran across a problem with the Navbars section in Onet.xml. Let me explain what I did.

I had a template which did not use the quick launch bars, and had them removed from the aspx files. So I thought of cleaning up the onet.xml also. If I completely removed the Navbars section from onet.xml, I believe my site was crasing on creation. So, I removed some of the Navbar sections in the process to tidy up my site definition, and kept the site settings stuff. Everything was fine. The system worked nicely and I had all my customisation working perfectly. Then I hit a serious glitch.

Go into any list and modify its settings, go to general settings, and try to toggle the list setting of On Quick Launch Bar. It will always reset to No, as soon as you click Ok. Many people had complained on the boards that they were unable to set the list to appear on the quick launch bar, and the setting toggled to No everytime. It seems the Navbar section was the source.

I replaced the Navbars section in my site’s onet.xml. But the damage was done. Any new sites which I create from this template, were fine. But the sites which were already created using the old template ( one without the Navbar sections ), did not allow me to toggle the quick launch bar setting at all. Only option was to delete and re-create those sites.

Also, I did not spend much time on this, but the list type which were removed from the Navbar section on onet, were the ones, affected with this problem.

I know it is not advisable to modify onet.xml, but we do not live in a perfect world. It is a necessary evil. But do not remove those navbar sections, even if you are not using the quick launch bar in your pages. Go ahead and remove it from the aspx pages, but keep the onet stuff in.

I still can’t figure out what’s the link to that setting and the Navbar section of onet.xml. After all, when I toggle that value, it is just a small update to one of the boolean fields in the database. No idea how is onet linked to that functionality. Anyways, to conclude, do not remove the Navbars section from the onet.xml.

I recently came across a very nice article on implementing caching in Web Parts. It describes the various options available for use and seems pretty nice. Have not read it completely yet, but thought of pointing you guys to it.

Check it out here.

In general, it is quite easy to remove the Category Navigation WebPart SPSWC:CategoryNavigationWebPart from the SharePoint template. Just open the proper file, locate

<SPSWC:CategoryNavigationWebPart runat=”server” id=”HorizontalNavBar” DisplayStyle=”HorizontalOneLayer” />

and delete it. ( The attributes may differ ).

On certain very stubborn pages, it is just not possible to remove it. For example, take the txtlstvw.aspx page. If you remove the category navigation webpart from this page, you are presented with the following error:

[NullReferenceException: Object reference not set to an instance of an object.]
Microsoft.SharePoint.Portal.WebControls.TextListingViewerPage.OnInit(EventArgs ea)
System.Web.UI.Control.InitRecursive(Control namingContainer) +240
System.Web.UI.Page.ProcessRequestMain() +195

I was very curious about it, as most of the pages do not complain so strongly if we remove the webpart from the template. There was no obvious link in the template HTML which proves that some other control uses it, and I removed almost all existing default controls from the page, but the error still persisted. This led me to believe that the error was somewhere in the code-behind for this page.

So I opened Reflector and loaded the Microsoft.SharePoint.Portal.dll and navigated to TextListingViewerPage->OnInit. There I found this piece of code :

this.HorizontalNavBar.CurrentCategoryID = this.BreadCrumbTrail.CurrentID = guid1.ToString();

There was no error checking code before this which tried to check if either HorizontalNavBar or BreadCrumbTrail objects were null. Thus we were stuck here. There is absolutely no way to remove these two webparts from this page without crashing it.

But… There was a sly approach. If I can’t remove them, then I can definitely hide them. My goal was to knock off these and add a custom branding with custom navigation controls. Hence, all I did was surround the Category Navigation Webpart and the Breadcrumb Trail Webpart with

<div style=”display:none;”>…</div>

Do this same trick if you ever have such a problem. I do remember having this problem while branding some other page in SharePoint but cannot remember which one. This is evidently sloppy coding on the part of the coder who wrote that page, and I hope problems like these would be corrected in the future releases.