How Do I Hide wpf datagrid row selector

Instead of setting the Width you can completely hide the row headers by setting on the DataGrid

HeadersVisibility="Column"

To remove the Row header(Gray field) in Datagrid in WPF

<DataGrid x:Name="TrkDataGrid" HeadersVisibility="Column">
</DataGrid>

To remove or hide the Column Header in DataGrid WPF

<DataGrid x:Name="TrkDataGrid" HeadersVisibility="Row">
</DataGrid>

To remove or hide both Column and Row Header in DataGrid WPF

<DataGrid x:Name="TrkDataGrid" HeadersVisibility="None">
</DataGrid>

Use the RowHeaderWidth property:

<my:DataGrid RowHeaderWidth="0" AutoGenerateColumns="False" Name="dataGrid1" />

Note that you can also specify a style or template for it also, should you decide you really do like it and want to keep it because you can do something cool with it.