How to get the DataRecord of all Record checked in the XamDataGrid


i have a Xamdatagrid with a field Checkbox on the Label  ,then i would like to enter in the values of all records that i checked (see photo below )   ....

with this is a code (i am using for  Button) i can get the 3 Records but from the First Row,Second Row and Third Row  instead i would like to get the records checked..

     for (int i = 0; i < xamDataGrid1.SelectedItems.Records.Count; i++)
                 string first = (xamDataGrid1.Records[i] as DataRecord).Cells[0].Value.ToString();
                 string second = (xamDataGrid1.Records[i] as DataRecord).Cells[1].Value.ToString();