Question

I have dynamically created textbox in asp.net. Now i am extracting the values through following code.

string[] sublist = new string[] { };
int[] maxmarkslist = new int[] { };
int i;
for (i = 0; i < Convert.ToInt32(Label15.Text); i++)
{
    string sub = "subject" + i;
    string marks = "maxmarks" + i;
    TextBox subject = (TextBox)PlaceHolder1.FindControl(sub);
    TextBox maxmarks = (TextBox)PlaceHolder1.FindControl(marks);
    sublist[i] = subject.Text;
    maxmarkslist[i] = Convert.ToInt32(maxmarks.Text);
}

But I getting error “Index was outside the bounds of the array” for the below two lines:

sublist[i] = subject.Text;
maxmarkslist[i] = Convert.ToInt32(maxmarks.Text);

When I debugged it, values are coming in subject.Text and maxmarks.Text but not going to array.

Did I define the array in a wrong way?

Answer 1

You define both the arrays as empty arrays. So you will get index out of bound erros if you try to index into those.

Arrays are not dynamically expanding. If you want that, use a collection type and may be later convert to an array.

Try this:

int length = Convert.ToInt32(Label15.Text);
string[] sublist = new string[length-1];
int[] maxmarkslist = new int[length-1];

for (int i = 0; i < length; i++)
{
    string sub = "subject" + i;
    string marks = "maxmarks" + i;
    TextBox subject = (TextBox)PlaceHolder1.FindControl(sub);
    TextBox maxmarks = (TextBox)PlaceHolder1.FindControl(marks);
    sublist[i] = subject.Text;
    maxmarkslist[i] = Convert.ToInt32(maxmarks.Text);
}

Or here is how to do this with a collection (List) type:

        int length = Convert.ToInt32(Label15.Text);
        List<string> sublist1 = new List<string>();
        List<int> maxmarkslist1 = new List<int>();

        for (int i = 0; i < Convert.ToInt32(Label15.Text); i++)
        {
            string sub = "subject" + i;
            string marks = "maxmarks" + i;
            TextBox subject = (TextBox)PlaceHolder1.FindControl(sub);
            TextBox maxmarks = (TextBox)PlaceHolder1.FindControl(marks);
            sublist1.Add(subject.Text);
            maxmarkslist1.Add(Convert.ToInt32(maxmarks.Text));
        }

        string[] sublist = sublist1.ToArray();
        int[] maxmarkslist = maxmarkslist1.ToArray();

Note with collections you dont have to specify the size upfront. But keep adding items to it as it can expand as needed. But arrays can not do this.

Your string[] sublist = new string[] { }; is a shortcut method where you create and initialize the array. In that you don’t have to specify the size, but compiler will count the elements between {} and set the size appropriately. In your case since there are no elements inside {} it will create an empty array.