Here is some code to get you started.
' This code assumes that you have bound a DataTable to the DataSource of a
DataGrid.
' This code also assumes that there is a column named "Bool" that is of type
Boolean.
' This code ensures that in a tri-state check scenario the "Indeterminate"
state is ignored.
Dim dt As DataTable = DirectCast(Me.DataGrid1.DataSource, DataTable)
For Each row As DataRow In dt.Rows
Dim obj As Object = row("Bool")
If (TypeOf obj Is Boolean) Then
If (DirectCast(obj, Boolean) = True) Then
' Get ID here.
' Example, Dim id As String = DirectCast(row("GUID"), String)
End If
End If
Next