Access system:string resource dictionary XAML in C#

How do I access the contents in a resource dictionary using C#?

For example, here is my code in XAML:

<system:String x:Key="NewGroup">New Group Name</system:S开发者_StackOverflow中文版tring>

And I want to access it here in C#:

    private void OnAddGroup(object sender, ExecutedRoutedEventArgs e)
    {

        BooksGroupInfo group = new BooksGroupInfo();
        group.GroupName = "New Group" + TheTabControl.Items.Count;
        TabItem tab = AddGroup(group);
        _currentLibrary.addGroup(group);
        _currentLibrary.CurrentGroup = group;

    }

Instead of typing "New Group" in C#, I would like to replace that and have access in the resource dictionary in XAML. So the command will automatically get the Name that is in the resource dictionary.

I've tried a couple of solutions like:

(System.String)this.FindResource("NewGroup"); 
Application.Current.Resources[typeof(System.String)]; 

and so on... but they do not seem to work.

I am doing a Localization using locbaml and it doesn't parse the Text/Name on C# (or I don't know how to) and that was the only solution I thought was possible.

Usually using FrameworkElement.FindResource like this: string s = this.FindResource("NewGroup") as string; works. It is more likely that the resource with the key "NewGroup" does not exist in the scope of your control or window (whatever this is). You must make sure that the resource is there. E.g. if your resource comes from another file you have to use MergedDictionaries. You can test if the resource is actually acessible try to acess it from XAML that belongs to your codebehind where OnAddGroup is definde.

I hope that makes sense.