my listview will display only the item that its added by the constructor and it wont add the items that i add dynamically

public class PostList : ObservableCollection<PostData>
{
    public PostList()
        : base()
    {

       Add(new PostData("Isak", "Dinesen"));
      //  Add(new PostData("Victor", "Hugo"));
      //  Add(new PostData("Jules", "Verne"));
    }
    public void AddToList (string[] data){
        string username2, msg;
        msg = data[0];
        username2 = data[1];

        Add(new PostData(msg, username2));

    }

}

public class PostData
{
    private string Username;
    private string Msg;
    private string Avatar;
    private string LinkAttached;
    private string PicAttached;
    private string VideoAttached;

    public PostData(string msg ,string username, string avatar=null, string link=null,string pic=null ,string video=null)
    {
        this.Username = username;
        this.Msg = msg;
        this.Avatar = avatar;
        this.LinkAttached = link;
        this.PicAttached = pic;
        this.VideoAttached = video;
    }

    public string pMsg
    {
        get { return Msg; }
        set { Msg = value; }
    }

    public string pUsername
    {
        get { return Username; }
        set { Username = value; }
    }

   .....
   .....
}

Xaml >

<ListView x:Name="PostListView" BorderThickness="0"
                  MinHeight="300" 
                  Background="{x:Null}"
                  BorderBrush="{x:Null}"
                  Foreground="{x:Null}"
                  VerticalContentAlignment="Top"
                  ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                  ScrollViewer.VerticalScrollBarVisibility="Disabled" IsSynchronizedWithCurrentItem="True"
                  MinWidth="332" SelectedIndex="0" SelectionMode="Extended" AlternationCount="1" ItemsSource="{Binding Source={StaticResource PostListData}}">
            <ListView.ItemTemplate>
                <DataTemplate>
                  <DockPanel x:Name="SinglePost" VerticalAlignment="Top" ScrollViewer.CanContentScroll="True" ClipToBounds="True" Width="333" Height="70" d:LayoutOverrides="VerticalAlignment" d:IsEffectDisabled="True">

            <StackPanel x:Name="AvatarNickHolder" Width="60">
                            <Label x:Name="Nick" HorizontalAlignment="Center" Margin="5,0" VerticalAlignment="Top" Height="15" Content="{Binding Path=pUsername}" FontFamily="Arial" FontSize="10.667" Padding="5,0"/>
                <Image x:Name="Avatar" HorizontalAlignment="Center" Margin="5,0,5,5" VerticalAlignment="Top" Width="50" Height="50" IsHitTestVisible="False" Source="1045443356IMG_0972.jpg" Stretch="UniformToFill"/>
            </StackPanel>
                        <TextBlock x:Name="userPostText" Margin="0,0,5,0" VerticalAlignment="Center" FontSize="10.667" Text="{Binding Path=pMsg}" TextWrapping="Wrap"/>
        </DockPanel>
    </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>