In a MVVM WPF app facing issue to bind a ViewModel function to the Checkbox present in the view

Question

I have a MVVM WPF app in which I have a View That Iam Displaying on the main window.

on click of the button Iam setting Data context of the MainWindow to ViewModel. And the Viemodel binding to View is working fine(ie Properties Initialised on the ViewModel are displaying data on the view).

Issue:-

<DataGridCheckBoxColumn  Binding="{Binding Path= 'IsSelected', UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" >
                    <DataGridCheckBoxColumn.HeaderTemplate>
                        <DataTemplate x:Name="SelectAllCheckBox">
                            <CheckBox Name="SelectAll" IsThreeState="False"  />
                        </DataTemplate>
                    </DataGridCheckBoxColumn.HeaderTemplate>                 
 </DataGridCheckBoxColumn>

this is my checkbox Which I want to bind In way so that on checking it I have DataContext object and can have access to the Perticular row of datagrid(Data in it) which it belongs.

:- not able to find solution to perticular problem stuck. Anything would be helpfull(ie. previous Solution or previous Question).