Object reference not set to an instance of an object Message with String Array

Question

I have the following code:

protected void btnSave_Click(object sender, EventArgs e)
{
    StarBusModel.BookingDetail1 objBooking = new StarBusModel.BookingDetail1();
    objBooking.TourID = tourID;
    objBooking.Name = txtName.Text;
    objBooking.Phone = txtPhone.Text;
    objBooking.Amount = Convert.ToDecimal(Request.Form[txtAmount.ClientID]);


    string []  seats = Request.Form[txtSeatNo.ClientID].Split(new char[] {','});
    for (int i = 0; i < seats.Length; i++)
            objBooking.SeatDetails.Add(new StarBusModel.SeatDetail1() {SeatID = Convert.ToInt32(seats[i])});
    objEntities.BookingDetail1.AddObject(objBooking);        
    objEntities.SaveChanges();
    BindSeats();
}

I get the error

System.NullReferenceException: Object reference not set to an instance of an object.

at the following code:

string []  seats = Request.Form[txtSeatNo.ClientID].Split(new char[] {','});

Please advise where I am wrong. I searched for various answers but cannot pinpoint where I am wrong.

this Request.Form[txtSeatNo.ClientID] may give you null??? — bitoshi.n
– bitoshi.n, Commented May 23, 2012 at 2:32
it is always good to perform a sanity check on your input form value before any manipulation. By the way, why you need to split the txtSeatNo ? — Turbot
– Turbot, Commented May 23, 2012 at 2:33
Why can't you access txtAmount.Text and txtSeatNo.Text? Why you need to get control values using form collection?? — Claudio Redi
– Claudio Redi, Commented May 23, 2012 at 2:33

Jacob · Accepted Answer · 2012-05-23 03:21:52Z

2

Request.Form[txtSeatNo.ClientID] is clearly null. In general, a NameValueCollection (like Request.Form) will return a null string if the given key is not defined.

You should do a check:

string seatString = Request.Form[txtSeatNo.ClientID];
string [] seats = String.IsNullOrEmpty(seatString) ? new char[]{} :
     seatString.Split(new char[] {','});

edited May 23, 2012 at 3:21

answered May 23, 2012 at 2:35

Jacob

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1 Comment

Nick Rodriquez Over a year ago

This helped me trace back the code and solve the null value returning for Request.Form[txtSeatNo.ClientID]. Thank a lot.

Coofucoo · Accepted Answer · 2012-05-23 07:05:20Z

0

NullReferenceException is a very headache excpetion. Even though you can know the line where the exception happen by see the stacktrace. But it may also include more than 1 possibilities.

Your case is an example.

string []  seats = Request.Form[txtSeatNo.ClientID].Split(new char[] {','});

In fact in this line, there are 2 place can cause null exception. They are:

txtSeatNo.ClientID
Request.Form[txtSeatNo.ClientID]

Normally the second is most possible.

So it is better to write the code in multiple lines and check the value before you use it. I think Jacob Abrahams gave a very good example.

answered May 23, 2012 at 7:05

Coofucoo

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