how to move from one tabitem to another in WPF

I have an ObservableCollection which I would bind to the ItemsSource and I have a property type of Tag which I will bind to the SelectedValue. Whenever I want to change the selected tab, I just set the selected value. Here's my dirty code. I hope this will help you with your problem.

<Window x:class="WpfApplication9.MainWindow" 
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication9"
        Title="MainWindow" Height="350" Width="525">
    <stackpanel>
        <tabcontrol itemssource="{Binding TagCollection}" selectedvalue="{Binding SelectedTag}">
            <tabcontrol.itemtemplate>
                <datatemplate>                    
                    <textblock text="{Binding Name}" />                    
                </datatemplate>
            </tabcontrol.itemtemplate>
        </tabcontrol>
        <button content="Test" command="{Binding ClickCommand}" />
    </stackpanel>
</window>

Here's the view model which I set to the data context of the view.
I created a click commant which will be triggered when you click the button. This will let you set the focus to TagCollection[1] (in a 0 based index it's the 2nd tab). Now the tricky part here is that you have to call raisepropertychange method on the setter. This will tell the view that someone set a new value for the SelectedTag and the view should update.

public class TagVM: ViewModelBase
{
    ObservableCollection<tag> tagCollection;
    public TagVM()
    {
        tagCollection = new ObservableCollection<tag>();
        tagCollection.Add(new Tag() { Name = "two", Priority = "2" });
        tagCollection.Add(new Tag() { Name = "another 2", Priority = "2" });
        tagCollection.Add(new Tag() { Name = "three", Priority = "3" });
        tagCollection.Add(new Tag() { Name = "one", Priority = "1" });
    }

    private Tag selectedTag;

    public Tag SelectedTag
    {
        get { return selectedTag; }
        set
        {
            selectedTag = value;
            base.RaisePropertyChanged("SelectedTag");
        }
    }

    public ObservableCollection<tag> TagCollection
    {
        get { return tagCollection; }
        set
        {
            tagCollection = value;
            base.RaisePropertyChanged("TagCollection");
        }
    }

    public ICommand ClickCommand
    {
        get
        {
            return new RelayCommand(() => { SelectedTag = TagCollection[1]; });
        }
    }
}