Why do I get a security validation invalid error updating a field from a feature receiver?

Question

Trying to change the title field of a document library to be required..doesn't want to work.

SPList docLib = web.Lists["Process Aids"];
SPField field = docLib.Fields["Title"];
field.Title = "Display Name";
field.Required = true;
field.Update();

Title shows up as Display Name. I saw something that said to allow unsafe updates. I tried that, but got an error saying that security validation was invalid.

Answer 1

I have tried this code snippet (from console application):

    using(SPSite site = new SPSite("http://mycoolsite"))
    {
        using(SPWeb web = site.OpenWeb())
        {
            SPList list = web.Lists["My List"];
            SPField fldTitle = list.Fields["Title"];
            fldTitle.Required = false;
            fldTitle.Title = "New title";
            fldTitle.Update();
        }
    }

and it works.

Edited: After reading comments I have changed code to FeatureActivated event:

    public override void FeatureActivated(SPFeatureReceiverProperties properties)
    {
        SPWeb web;
        SPSite site;

        //Parent can be site or web depending on feature scope
        object oParent = properties.Feature.Parent;
        if (properties.Feature.Parent is SPWeb)
        {
            web = (SPWeb)oParent;
            site = web.Site;
        }
        else
        {
            site = (SPSite)oParent;
            web = site.RootWeb;
        }

        SPList list = web.Lists["My List"];
        SPField fldTitle = list.Fields.GetFieldByInternalName("Title");
        fldTitle.Required = false;
        fldTitle.Title = "New title";
        fldTitle.Update();

    }

If you have some 'strange' permissions on your web and if user have permissions to activate feature and doesn't have permissions on list you could wrap code in SPSecurity.RunWithElevatedPrivileges as @VadimLozinskiy suggested.

To summarize: I have tested above code and I really think is valid. If you are still receiving errors on feature activation your problem is elsewhere. To troubleshoot it try to build another simple feature using above code to test if your environment is 'acting as expected'.

Answer 2

Hi WCHolland try this code

SPSecurity.RunWithElevatedPrivileges(delegate
{
using(SPSite curSite = new SPSite(((SPSite)properties.Feature.Parent).Url)
    {
        using(SPWeb web = curSite.OpenWeb())
        {
          SPList docLib = web.Lists["Process Aids"];
          SPField field = docLib.Fields["Title"];
          field.Title = "Display Name";
          field.Required = true;
          field.Update();
        }
    }
}

Changed code after reading comments