WPF datagrid's cells contain a border on their left sides

My WPF DataGrid contains an extra item which can be highlighted when hovering the mouse over it.

Which exact property is used to enable/disable it?

The following is a snippet of the XAML code used:

<DataGrid x:Name="DgMonitor" Grid.Row="0" Margin="10,10,10,5" Background="White" CanUserAddRows="False" RowHeight="34"
            AutoGenerateColumns="False" HorizontalGridLinesBrush="Transparent" VerticalGridLinesBrush="Transparent"
            GridLinesVisibility="All" HeadersVisibility="All" CanUserReorderColumns="False" CanUserSortColumns="False" CanUserResizeColumns="False" CanUserResizeRows="False"
            VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" SelectionMode="Single" SelectionUnit="FullRow">
     <DataGrid.Columns>
        <DataGridTemplateColumn Width="*">
          <DataGridTemplateColumn.CellTemplate>
              <DataTemplate>
                 <Grid Margin="5,0,10,0" >
                    <Grid.ColumnDefinitions>
                       <ColumnDefinition Width="*"/>
                       <ColumnDefinition Width="Auto"/>
                       <ColumnDefinition Width="Auto"/>
                       <ColumnDefinition Width="Auto"/>
                    </Grid.ColumnDefinitions>
                    <TextBlock Grid.Column="0" Margin="0,0" VerticalAlignment="Center" TextWrapping="Wrap"/>
                    <Button Grid.Column="1" Width="20" Height="20" Margin="2"/>
                    <Button Grid.Column="2" Width="20" Height="20" Margin="2"/>
                    <Button Grid.Column="3" Width="20" Height="20" Margin="2"/>
                 </Grid>
              </DataTemplate>
           </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
       </DataGridTemplateColumn>
     </DataGrid.Columns>
  </DataGrid>

>Solution :

Update this…

<DataGrid x:Name="DgMonitor" Grid.Row="0" Margin="10,10,10,5" Background="White" CanUserAddRows="False" RowHeight="34"
            AutoGenerateColumns="False" HorizontalGridLinesBrush="Transparent" VerticalGridLinesBrush="Transparent"
            GridLinesVisibility="All" HeadersVisibility="All" CanUserReorderColumns="False" CanUserSortColumns="False" CanUserResizeColumns="False" CanUserResizeRows="False"
            VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" SelectionMode="Single" SelectionUnit="FullRow">

…to include…

RowHeaderWidth="0"

And/or you may also wish to consider changing HeadersVisibility="All" to something more apt, such as HeadersVisibility="Column"