WPF fills mockup data in ListView

Using blend to do visual design, often encounter problems that don't know how to go to ListView for vacation data. This provides a method. For your reference. If there is a simpler way, I hope you will not hesitate to enlighten us.

The code is as follows:

<window
Xmlns= "Http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x= "Http://schemas.microsoft.com/winfx/2006/xaml"
Xmlns:s= "Clr-namespace:system;assembly=mscorlib"
X:class= "Listviewdata.mainwindow"
X:name= "Window"
title= "Demo window"
Width= "height=" >
<grid x:name= "LayoutRoot" >
<ListView>
<ListView.View>
<GridView>
<gridviewcolumn header= "Value"
Displaymemberbinding= "{Binding.}" />
<gridviewcolumn header= "Length"
displaymemberbinding= "{Binding Length}"/>
</GridView>
</ListView.View>
<ListView.Items>
<s:String>a</s:String>
<s:String>bb</s:String>
</ListView.Items>
</ListView>
</Grid>
</Window>