Listbox Databinding in wpf

try this

Create DataTemplate in resource section and then assign it to listbox

<Grid.Resources>
        <DataTemplate x:Key="userNameTemplate">

                <TextBlock Text="{Binding Path=UserName}"/>

        </DataTemplate>

 <ListBox Name="listBox" ItemsSource="{Binding}"
            ItemTemplate="{StaticResource userNameTemplate}"/>