How to remove extra column Datagrid

Solution 1 :

Set AutoGenerateColumns="False" and Width="*" for all Columns

 <DataGrid x:Name="dataGrid" IsReadOnly="True" AutoGenerateColumns="False">
    <DataGrid.Columns>
       <DataGridTextColumn Binding="{Binding OrderId}" Header="OrderId" Width="*"/>
       <DataGridTextColumn Binding="{Binding ProductId}" Width="*" Header="ProductId"/>
       <DataGridTextColumn Binding="{Binding UnitPrice}" Width="*" Header="UnitPrice"/>
       <DataGridTextColumn Binding="{Binding Quantity}" Width="*" Header="Quantity"/>
       <DataGridTextColumn Binding="{Binding Discount}" Header="Discount"
                           Width="*"/>
    </DataGrid.Columns>
</DataGrid>

Solution 2 : You can set like this to achieve your requirement

<DataGrid HorizontalAlignment="Left" Margin="50,0,0,0" Width="500"
          Name="dataGrid"  IsReadOnly="True"  VerticalAlignment="Top"
          ItemsSource="{Binding Cus}" AutoGenerateColumns="True"/>


 this.dataGrid.AutoGeneratingColumn += dataGrid_AutoGeneratingColumn;

 void dataGrid_AutoGeneratingColumn(object sender, 
                                    DataGridAutoGeneratingColumnEventArgs e)
 {
     e.Column.Width = new DataGridLength(1, DataGridLengthUnitType.Star);
 }

One way to avoid is to set AutoGenerateColumns to False (XAML only approach).

Provide your own collection of columns and set width for last column to *.

<DataGrid x:Name="dataGrid" IsReadOnly="True" AutoGenerateColumns="False">
    <DataGrid.Columns>
       <DataGridTextColumn Binding="{Binding OrderId}" Header="OrderId"/>
       <DataGridTextColumn Binding="{Binding ProductId}" Header="ProductId"/>
       <DataGridTextColumn Binding="{Binding UnitPrice}" Header="UnitPrice"/>
       <DataGridTextColumn Binding="{Binding Quantity}" Header="Quantity"/>
       <DataGridTextColumn Binding="{Binding Discount}" Header="Discount"
                           Width="*"/>
    </DataGrid.Columns>
</DataGrid>

Replace bindings for your columns to corresponding properties in your model class. Output will be like this:

However, in case you want to distribute available space equally for all columns. You can set width to * for all columns. Output will be like this:

You can set the HorizontalAlignment to Left. As described here

For example:

<DataGrid ItemsSource="{Binding}" HorizontalAlignment="Left"/>