web.config Entries not Being Removed During Feature Deactivation

Question

I'm writing a web application scoped feature receiver to make changes to web.config using SPWebConfigModification. Adding entries is working well. My problem is removing the entries. When stepping through the debugger, I can see them being discovered by Owner name and removed from the WebConfigModifications collection. However, on inspection of the web.config file, these entries are still present. In my ULS I can see the FeatureReceiver running and completing for FeatureDeactivating. There are no other entries.

Does anyone have any ideas on what to do to?

public override void FeatureDeactivating(SPFeatureReceiverProperties properties){
    SPWebApplication webApp = properties.Feature.Parent as SPWebApplication;
    Collection<SPWebConfigModification> modsToRemove = new Collection<SPWebConfigModification>();

    foreach (SPWebConfigModification mod in webApp.WebConfigModifications)
    {
        if (mod.Owner == "MyUniqueName")
            modsToRemove.Add(mod);
    }

    if (modsToRemove.Count > 0)
    {
        int count = modsToRemove.Count;

        for (int i = 0; i < count; i++)
        {
            webApp.WebConfigModifications.Remove(modsToRemove[i]);
            webApp.Update();
        }
        webApp.WebService.ApplyWebConfigModifications();
    }
}

Answer 1

It appears that this is because you are calling ApplyWebConfigModifications() on the wrong SPWebService object.

From How To: Modify the web.config file in SharePoint using SPWebConfigModification:

Use the ApplyWebConfigModifications() method on the SPWebApplication object you are saving your SPWebConfigModification object to. I don’t understand why this works over the other way, but it solved the problem for me. Example:

myWebApp.Farm.Services.GetValue<SPWebService>().ApplyWebConfigModifications();

Note: This code did not work across the farm (I could not tell you why).

SPFarm.Local.Services.GetValue< SPWebService>().ApplyWebConfigModifications();

Try this:

if (modsToRemove.Count > 0)
{
    int count = modsToRemove.Count;

    foreach (SPWebConfigModification modToRemove in modsToRemove)
    {
        webApp.WebConfigModifications.Remove(modToRemove);
        webApp.Update();
    }
    webApp.Farm.Services.GetValue<SPWebService>().ApplyWebConfigModifications();
}