How to iterate through the Datagrid in WPF?

Question

I have a datagrid view in my WPF .Where i map an item source in it.Datagrid view contains checkboxes in all rows.User may check or uncheck some rows.So i want to iterate through the datagrid row and cell values to know the selected rows .I tried all things present in Internet but nothing helps.please help me to solve my pbm