不能从listview中获取文本

XAML code:

XAML代码:

<ListView.View>
    <GridView x:Name="myGridView">
        <GridViewColumn Width="0" DisplayMemberBinding="{Binding Id}">
            <GridViewColumnHeader Content="Id" IsHitTestVisible="False" />
        </GridViewColumn>
        <GridViewColumn Width="50" Header="Cant">
            <GridViewColumn.CellTemplate>
                <DataTemplate>
                    <TextBox FontSize="11" />
                </DataTemplate>
            </GridViewColumn.CellTemplate>
        </GridViewColumn>
        <GridViewColumn Width="300" Header="Nombre" DisplayMemberBinding="{Binding Nombre}" />
    </GridView>
</ListView.View>
<ListView.View>
    <Gri