Object reference not set to an instance of an object in gridview data source

Question

hi friends

i have a shopping cart that has a button for add to cart;
here , there are my codes for click event of the button:

 protected void AddToCart(object sender, ImageClickEventArgs e)
    {
        UserControl cart = (UserControl)Master.FindControl("cart1");
        DataGrid mydg = (DataGrid)cart.FindControl("dg");
        Label lbl = (Label)cart.FindControl("lblTotal");

        product = productName;
        DataTable objDT = (DataTable)Session["Cart"];

        foreach (DataRow objDR in objDT.Rows)
        {
            if (objDR["product"] == product)
            {
               // objDR["Quantity"] = int.Parse(objDR["Quantity"].ToString()) + int.Parse(txtQuantity.Text);
                objDR["Quantity"] = int.Parse(objDR["Quantity"].ToString()) + 1;
                blnMatch = true;
            }
        }
        if (blnMatch == false)
        {
            objDR = objDT.NewRow();
            objDR["Quantity"] = quantity;
            objDR["Product"] = productName;
            objDR["Cost"] = Decimal.Parse(productcost);
            objDT.Rows.Add(objDR);
        }
        Session["Cart"] = objDT;
        mydg.DataSource = objDT;
        mydg.DataBind();
        lbl.Text = "????" + GetItemTotal();
    }

at pink line i get the error

 Object reference not set to an instance of an object.

how can i set that?

Sam Hobbs · Answer

When you get that error while debugging you need to look at the data to see what is not set. I assume that mydg is not set but it would help to know for sure. So assuming that mydg is not set then obviously the line: DataGrid mydg = (DataGrid)cart.FindControl(dg); Is not working. You need to use try/catch blocks whenever there is a possible problem such as this. Assuming that mydg is not set you need to at least diagnose and fix that.

Bahar Jalali · Answer

thx all my friends all ideas were good and help me i change the datagrid with a gridview and i forgot change it in the code but by your help i understand that thanks for advance

jinge · Answer

@ kirtan If the datatable is null then such exception can not be happened. It makes sense to assign the DataSource to null. The only possible cause is the datagrid is a null reference.

Kirtan Patel · Answer

Friend this can be happening because of your Session[Cart] may be returning null. check if Session[Cart] is Null ??? because it can be the cause of problem . if (Session[Cart] !=null) { //All your Code Here } else { Response.Write(Cart is Null); } if my answer helps you then  check Do you like this answer check box  please :) if still having problem then let me know . or you can send me your project Files(Zip) with database at kirtan007@gmail.com i will resolve your problem :)