C＃foreach超出范围

Question

For some reason, my array summary , subject and date are getting use of unassigned local variable errors. Does anybody know whats going on?

    int count = 0;
    string[] summary;
    string[] subject;
    string[] date;

    foreach (SyndicationItem item in feed.Items)
    {
        subject[count] = item.Title.Text;
        date[count] = item.PublishDate.DateTime.ToString();

        summary[count] = item.Summary.Text;
        list.InnerHtml += "<a href=\"#\" onclick\"showArticle(" + count + ");\"><li id=\"post" + count + "\"><b>" + subject[count] + "</b><br>" +
           "<p id=\"posted-date\">Posted on: " + date[count] + "</p>" + "</li></a>";
        count++; 
    } 

Answer 1

You need to initialize the arrays to a particular size, eg:

string[] summary = new string[feed.Items.Count()];

Alternatively, you can use a List<String> instead of an array if you don't know or care about the length of the arrays. A list is actually preferable in your situation, as the Count() extension method will unnecessarily enumerate feed.Items prior to your loop.

Answer 2

You never assign a value to the array, you only ever access the array through its indexer even though you never created it. You could initialize them like so:

string[] summary = new string[feed.Items.Count];
string[] subject = new string[feed.Items.Count];
string[] date = new string[feed.Items.Count];

Answer 3

They are not initialized . You should complete the declaration like:

string[] summary = new string[feed.Items.Count];
string[] subject = new string[feed.Items.Count];
string[] date = new string[feed.Items.Count];

Answer 4

You need to initialize the arrays before you can use them, like this:

string[] summary = new string[length];

However, in this case you don't know the length beforehand, because feed.Items is an IEnumerable<SyndicationItem> , so you can't get the number of items directly (you could use .Count() , but it would make you enumerate the collection several times, which is usually not recommended).

A better approach would be to use lists instead of arrays:

List<string> summary = new List<string>();

...

summary.Add(item.Summary.Text)

...

Answer 5

Previous answers have correctly identified that you need to initialize the array variables with the size of the array. To think about why this is necessary realize that at the start of the foreach loop the program has no idea how much memory these arrays are going to take up. It would be impossible to say where in memory summary[count] is going to point to!