Getting exception inside datagridview looping.

Question

Hi all expert, I have two fields in data grid one comboxbox type another is texbox type. As per user selection I want to add multiple record at a time in backend. Here is my looping code…pls somebody help………help…help………me..inside looping code I am getting casting exceptions. Unable to cast object of type 'System.String' to type 'Create_Sales_Back_Order.DynamicsGPService.SalesBackorderLine[]'.

for (int counter = 0; counter < (CreateSalesBackOrderGrid.Rows.Count); counter++) { salesBackorder.Lines = (SalesBackorderLine[])CreateSalesBackOrderGrid.Rows[counter].Cells[0].Value; //here getting this exception. //here I should write insert method. }