How to setup error checking for arrays?

Question

I am using HTML agility pack and parsing to an array.

The information I am parsing changes and when it changes below a certain level I get unhandled exceptions because I am trying to bind the an element [][] that isn't there.

How would I setup error checking to make sure if the array isn't there it wouldn't throw an Unhandled expection?

Eg... If I use the below code and there is no [2][1] then I get an exception, but the html changes so It needs to cope with null dor non existant arrays elements

    //first line
    textBlock1.Text = node[0][0];
    textBlock2.Text = node[0][1];
    textBlock3.Text = node[0][2];

    //first line
    textBlock4.Text = node[1][0];
    textBlock5.Text = node[1][1];
    textBlock6.Text = node[1][2];

    //first line
    textBlock7.Text = node[2][0];
    textBlock8.Text = node[2][1];
    textBlock9.Text = node[2][2];

Array is from this code:

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
    var html = e.Result;

    var doc = new HtmlDocument();
    doc.LoadHtml(html);

    var list = doc.DocumentNode.Descendants("div").ToList();

    var node = doc.DocumentNode.Descendants("table")
         .FirstOrDefault(x => x.Id == "departures")
        .Element("tbody")
         .Elements("tr")
          .Select(tr => tr.Elements("td").Select(td => td.InnerText).ToArray())
          .ToArray();

Is this a multidimensional array or a jagged array? You imply that it's multidimensional, but in that case if [2][1] is not valid it means that all of the third row or the second column will not be valid. — Jon
– Jon, Commented Sep 15, 2011 at 7:43
Can you add some more code? I can't tell from the code you've posted it's an array - can be just types with indexers — Amittai Shapira
– Amittai Shapira, Commented Sep 15, 2011 at 7:48
@jon its a multidimensional array. The array size is based on HTML parse, os sometimes all the rows are not valid and thats what I want to error check. Check if the array exists before binding. — Rhys
– Rhys, Commented Sep 15, 2011 at 9:13

Amittai Shapira · Accepted Answer · 2011-09-15 08:09:28Z

1

You can check length for both dimensions, e.g.

if (node.Length > 2)
{
   //first line
   if (node[2].Length > 0)
   {
      textBlock7.Text = node[2][0];
   }
}

edited Sep 15, 2011 at 8:09

answered Sep 15, 2011 at 7:13

Amittai Shapira

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6 Comments

Rhys Over a year ago

Using a conditional? Or how would I implement?

Rhys Over a year ago

Thanks for the suggestion, but it wont let me use node[0] as it is an [][] array.

Amittai Shapira Over a year ago

I've edited again :-) What is the exact type of node? is it really multidimensional array, or just some type with indexers?

Rhys Over a year ago

Thanks for your help. but still not working, error: operator && cannot be applied to Bool or int. The array is a combination. It is a list of the 3 values, each line has three values. PLacename, number, number.

Amittai Shapira Over a year ago

Ok, it is an multi-dimensional array :-) fixed my code last time, next time I should be using compiler :-)

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