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

Bahar Jalali

17y15.4k.NET

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?

4 Replies

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Sam Hobbs17y ago
Accepted 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 Jalali17y ago
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
jinge17y ago
@ 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 Patel17y ago
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 [email protected]

i will resolve your problem :)