How to add a custom action to a SharePoint list actions menu for a specific list or content type.

If you have ever tried adding a SharePoint custom action to the actions menu and tried using "List" or "ContentType" as the "RegistrationType" and then tried to specify a specific list or content type in the "RegistrationId" you know that it doesn't work. SharePoint will silently not render your custom action. If you try and target a generic list using a "RegistrationId" of "100" you will see that SharePoint will gladly render your action on every list in the site. I have found a rather kludgy work around to the problem.

First off in your element manifest file you need to use the "ControlAssembly" and "ControlClass" attributes off of CustomAction. MSDN doesn't say a whole lot about these attributes but essentially they allow you to specify a web control class in your assembly which can render the action. (If you need to create hierarchical menus check out this article.) Here is the XML to get you started:

<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <CustomAction
    Id="MyCustomAction"
    RegistrationType="List"
    GroupId="ActionsMenu"
    Location="Microsoft.SharePoint.StandardMenu"
    Sequence="1000"
    ControlAssembly="[Fully qualified assembly name]"
    ControlClass="MyNamespace.MyCustomAction">
  </CustomAction>
</Elements>

Next you will need to create a web control class which renders the menu item, as seen below:

public class MyCustomAction : WebControl {
  private MenuItemTemplate _action;

  protected override void CreateChildControls() {
    SPWeb site = SPContext.Current.Web;

    _action = new MenuItemTemplate {
      Text = "My Action",
      Description = "My Action",
      ImageUrl = "/_layouts/images/NEWITEM.GIF",
      ClientOnClickNavigateUrl = "http://www.nearinfinity.com"
    };

    Controls.Add(_action);
  }
}

Compile and deploy your solution. Oh and make sure to add your assembly and namespace to the safe control list or you will end up pulling your hair out because once again SharePoint will silently not render your menu item. You should now see the "My Action" on every list in the site. We have now reproduced what a standard CustomAction element in your element manifest would do normally. Now we need to find a way to determine which list our control is being added to. The best way I found for doing that is to traverse the control hierarchy up the parent chain until I found the containing ListViewWebPart. The code is quite simple and looks like this:

private ListViewWebPart GetParentListViewWebPart() {
  Control parent = Parent;
  while (parent != null) {
    if (parent is ListViewWebPart) {
      return (ListViewWebPart)parent;
    }
    parent = parent.Parent;
  }
  return null;
}

You should know where I'm going with this now, but for completness I will show you the last piece of code below which restricts it to a single list instance:

private Guid TARGET_LIST_ID = new Guid ("0D9B9302-8599-4CE5-8695-1B95FE7378F1");

protected override void OnLoad(EventArgs e) {
  base.OnLoad(e);
  if (!Page.IsPostBack) {
    EnsureChildControls();
    _action.Visible = false;
    ListViewWebPart listView = GetParentListViewWebPart();
    if (listView != null) {
      Guid listGuid = new Guid(listView.ListName);
      if (TARGET_LIST_ID == listGuid) {
        _action.Visible = true;
      }
    }
  }
}

Now that we have the list Guid that our control is being rendered for I will leave it as an exercise to the reader to restrict it to a given content type.

Why SharePoint doesn't provide this kind of functionality out of the box amazes me, but at least they provide a powerful API that you can get in there and work around it in a not so horribly kludgy way. Maybe SharePoint 2010 will include this :)