Checked items of checkbox of datagridview c#

I have added checkbox in datagridview and I want check whether an item is checked or not but I am little bit confuse how to accomplish it.
This is Xmal code

<DataGrid.Columns>
                    <DataGridTemplateColumn Header="#">
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <CheckBox x:Name="checkboxinstance" Checked="checked_it" Unchecked="unchecked_it"/>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>
                    <DataGridTextColumn Binding="{Binding apiName }" Header="Name"   />
                </DataGrid.Columns>

This is behind the code

private void checked_it(object sender, RoutedEventArgs e)
    {
        List<CheckBox> checkBoxlist = new List<CheckBox>();
   foreach (CheckBox c in checkBoxlist)
   {
     //what I add here
   }
  }

If anyone know solution kindly help