SPWeb.GetList() - Cannot Complete this Action

Question

SPWeb.GetList() on an application page throws an exception ("Cannot Complete this Action") during postback. For some reason the first request to the application page seems to work.

on an application page I have the following code which works fine:

SPWeb contextWeb = SPContext.Current.Web;
SPList listByTitle = contextWeb.Lists["MyList"]; //works
SPList listByRelativeUrl = contextWeb.GetList("/sites/MySiteCollection/Lists/MyList"); //works

Then I call the exact same code from an event handler in the same application page

void Btn_Click(object sender, EventArgs e)

where

SPList listByTitle = contextWeb.Lists["MyList"]; //works
SPList listByRelativeUrl = contextWeb.GetList("/sites/MySiteCollection/Lists/MyList"); //throws

Background: I am creating lists via code during feature activation and would like to access them without displaynames / titles nor Guids after the deployment. Currently I use SPWeb.GetList() but I'd be interested in another approach as SPWeb.GetList() seems to perform rather poorly. Linq4SP is not an option due to the lack of support for anonymous users.

Answer 1

It's better if you use the GUID instead of the staticnames.

But I always use SPWeb.Lists[], only on rare occasions i use the GetList() method. (when getting a list from a full url for example).

this code works fine for me:

SPList oList = SPContext.Current.Web.GetList("/sites/sitename/Lists/ListName");

But please keep in mind, the documentation will tell you that the GetList() method accepts a parameter containing a SITE relative url to the list. This is wrong, you have to enter a SERVER relative url.

Wrong:

SPList oList = SPContext.Current.Web.GetList("/Lists/ListName");
SPList oList = SPContext.Current.Web.GetList("/ListName");

Correct:

SPList oList = SPContext.Current.Web.GetList("/sites/sitename/Lists/ListName");

Also make sure that the List is located in the same Web as the SPWeb object.

Correct:

SPWeb oWeb = new SPSite("http://localhost/sites/testsite").RootWeb;
//The above code should be written better, (using statement etc)

SPList oList = oWeb.GetList("/sites/testsite/Lists/ListName");

Wrong:

SPWeb oWeb = new SPSite("http://localhost/sites/testsite").RootWeb;
//The above code should be written better, (using statement etc)

SPList oList = oWeb.GetList("/sites/testsite2/Lists/ListName");

Enjoy :-)

Answer 2

Along with the points suggested by Frederik, you can try something

using (SPSite curSite = new SPSite(SPContext.Current.Web.Url))
                {
                    curSite.AllowUnsafeUpdates = true;
                    using (SPWeb curWeb = curSite.OpenWeb())
                    {
                        curWeb.AllowUnsafeUpdates = true;
                        SPList list2 = curWeb.GetList(SPUrlUtility.CombineUrl(curWeb .ServerRelativeUrl.TrimEnd('/'), "/Lists/ListName"));
                        curWeb.AllowUnsafeUpdates = false;
                    }
                    curSite.AllowUnsafeUpdates = false;
                }

The allow unsafe updates are the key here, i was also getting the same exception and the above code works for me.