Nested foreach within dynamically created CheckBoxList

Question

I have a dynamically created CheckBoxList. Within this CheckBoxList, I have a nested foreach loop used to validate a user input. The user enters his or her email address. Once the user clicks submit, the CheckBoxList is created. If the user's email matches a subscription to a topic, the checkbox next to that topic is selected. The problem I'm having is relating the original outer foreach to the nested foreach.

int i = 0;
foreach (Topic topic in result)
{
    string topicName = topic.TopicArn.ToString().Split(':').Last();
    ListItem li = new ListItem(topicName, topic.TopicArn);
    checkBoxList1.Items.Add(li);

    foreach (Subscription subscription in subs) // where topic equals current 
                                                // topic in original foreach?
    {
        if (txtEmail.Text == subscription.Endpoint)
            checkBoxList1.Items[i].Selected = true;
    }
    i++;
}

I was thinking I might be able to use LINQ to add a condition to the nested foreach loop, but I haven't been able to pull it all together yet.

EFeit · Accepted Answer · 2012-12-19 20:12:15Z

1

You must first create all the checkboxes before you can start evaluating if they should be checked or not. In the code above you create one Listitem then you loop thru all the subscribtions so it will go out of bound in that loop before you create the second listitem in the checkboxlist.

 foreach (Topic topic in result)
 {
   string topicName = topic.TopicArn.ToString().Split(':').Last();
   ListItem li = new ListItem(topicName, topic.TopicArn);
   li.Selected = subs.Any(s => s.Endpoint == txtEmail.Text && s.TopicArn == topic.TopicArn);
   checkBoxList1.Items.Add(li); 
 }

edited Dec 19, 2012 at 20:12

EFeit

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answered Dec 19, 2012 at 18:43

Mattias Josefsson

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3 Comments

EFeit Over a year ago

I appreciate the response, because normally you would be exactly right! I need to be more clear. Each topic can have multiple subscribers. For each of the topics I need to check if the user's email matches any of the subscribers. Then I need to increase the counter and iterate to the next topic. The above throws an ArgumentOutOfRangeException because there are 4 subscriptions and 3 topics (CheckBoxList items). This is a very good start though, so thank you for the help.

Mattias Josefsson Over a year ago

Ok, now I have modified my answer to solve your problem with one foreach loop with a linq expresseion that checks for a match beetween Endpoint and txtEmail and if it finds a match returns true.

EFeit Over a year ago

Perfect! I modified your answer slightly to make sure the topic and subscription we were testing for were related. Can't thank you enough!

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