Wpf ListView add items not add items but add name of items

I try to add items to listview but not working well.Just display name of items .How do i fix it?

xmal:

<ListView x:Name="lv"  Height="300" Margin="0,10,0,125">
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Name" Width="300" DisplayMemberBinding="{Binding Name}"/>
            <GridViewColumn Header="Age"  Width="300"  DisplayMemberBinding="{Binding Age}"/>
        </GridView>
    </ListView.View>
</ListView>
<Button Content="Button" HorizontalAlignment="Left" Margin="371,393,0,0" VerticalAlignment="Top" Click="Button_Click"/>

cs:

private void Button_Click(object sender, RoutedEventArgs e)
{
    lv.Items.Add(new Myitem(){Age="20",Name="Nametest" });
}

cs:

public class Myitem
{
    public string Name { get; set; }
    public string Age { get; set; }
}