A wpf DataGrid has this DataGridTemplateColumn:

<DataGridTemplateColumn.CellTemplate>
  <DataTemplate>
     <Grid Margin="0">
       <ListView .....>
           ...
       </ListView>
     </Grid>
  </DataTemplate>
</DataGridTemplateColumn.CellTemplate>

The ListView has

 <ListView.View>
     <GridView>
     ...

with four GridViewColumn’s each with a DataTemplate.
One DataTemplate with a TextBox, one with a TextBlock, two with Label.

What I don’t get is, why the Height of these TextBox / TextBlock / Label
does not want to stretch to the height of the DataGridRow.

It looks as if there is a Margin or Padding between the edges of DataGridRow and the control of the DataTemplates.

E.g. the desired height of the lowest level controls is 16 pix. but the datagridcell has a
height of 20 pix.

Every Margin and Padding is set to 0 (zero) and every VerticalAlignment or VerticalContentAlignment is set to Stretch.

I cannot get rid of the “gap”. Any idea why this is so difficult?