<myControl:Explorer ExplorerControlRootPath="c:\temp"></myControl:Explorer>

public string ExplorerControlRootPath
        {
            get { return this.rootPath; }
            set {this.rootPath = value;}
        }

this.DokumentBrowser.ItemsSource = ";

this.DokumentBrowser.ItemsSource = fileOP.list_directory("c:\temp");

protected static readonly DependencyProperty ExplorerControlRootPathProperty = DependencyProperty.Register("ExplorerControlRootPath", typeof(string), typeof(Explorer));

public string ExplorerControlRootPath
        {
            get { return GetValue(ExplorerControlRootPathProperty) as string; }
            set { SetValue(ExplorerControlRootPathProperty, value); }
        }