private void XamWebGrid_CellExitingEditMode(object sender, ExitEditingCellEventArgs e)
        {           
            Infragistics.Silverlight.Controls.RowBase r = e.Cell.Row;           
            // Ensure using correct cell and editing has not been cancelled           
            if (e.Cell.Column.Key == "StepDescription" && !e.EditingCanceled)
            {
                ComboBox box = e.Editor as ComboBox;
                if (box.SelectedItem != null && ((ListItem)box.SelectedItem).Value!="0")
                {
                    Web.Cortex.WcfServiceReference.TestStepsProfile obj = new Web.Cortex.WcfServiceReference.TestStepsProfile(); ;
                    int StepId = Int32.Parse(((ListItem)box.SelectedItem).Value);
                    if (TestStepscollection != null && TestStepscollection.Count > 0)
                    {
                        var TestStepsMatch = TestStepscollection.Where(p => p.StepID == 6620);
                        //IEnumerable<Web.Cortex.WcfServiceReference.TestStepsProfile> qry = from c in TestStepscollection
                        //                                                                   where c.StepID == 6620
                        //                                                                   select c;                                               
                        //ObservableCollection<Web.Cortex.WcfServiceReference.TestStepsProfile> filteredClients = new ObservableCollection<Web.Cortex.WcfServiceReference.TestStepsProfile>(qry);

                        //IEnumerable<Web.Cortex.WcfServiceReference.TestStepsProfile> matches = TestS//tepscollection.Where(p => p.StepID == 6620);
                        foreach (Web.Cortex.WcfServiceReference.TestStepsProfile TestStep in TestStepsMatch)
                        {                           
                            rr.Cells["StepObjectClass"].Content = TestStep.StepObjectClass;
                            r.Cells["StepObjectClass"].Content = TestStep.StepObjectClass == null ? "" : TestStep.StepObjectClass;
                            r.Cells["StepObjectName"].Content = TestStep.StepObjectName == null ? "" : TestStep.StepObjectName;
                            //r.Cells["StepObjectAction"].Content = TestStep.StepObjectAction == null ? "" : TestStep.StepObjectAction;                           
                            r.Cells["StepID"].Content = TestStep.StepID == null ? "" : TestStep.StepID.ToString();
                            r.Cells["StepOrder"].Content = e.Cell.Row.Index + 1;                           
                            gridTransaction.Rows.Add((Row)r);                           
                            //TestStep.StepOrder = e.Cell.Row.Index + 1;
                            //TestStepList.Add(TestStep);                                   
                        }                       
                    }
                   
                    // New value is value of selected item in combo box
                    ////e.NewValue = ((ListItem)box.SelectedItem).Text;
                    box.ItemsSource = null;
                    box.SelectedItem = null;
                }
            }
        }

In above code I want to add the row in the grid.But as am doing

Infragistics.Silverlight.Controls.RowBase r = e.Cell.Row;  So the same row get copied again...

So anyone help me how to add new row in grid.I don't want to do it by modifying the collection object.