CODEWITHSUNDEEP
c#arrayslist
PKD
PKD

Reputation: 707

How to quickly cut up and reassemble a C# List?

The setup: I have a session variable that carries a list of IDs, pipe-delimited. The IDs are related to views in my site, and related to a breadcrumb builder.

Session["breadCrumb"] = "1001|1002|1003|1004";

If I'm on the view that corresponds to 1002, I'd like to cut everything AFTER that id out of the session variable.

I'd thought to use something like:

var curView = "1002";

if (Session["breadCrumb"] != null) {
    var crumb = Session["breadCrumb"].ToString().Split('|').ToList();
    var viewExists = crumb.Any(c => c.Value == curView);

    if (viewExists) {
        //remove everything after that item in the array.
    }

}

But I'm wide open to methodologies.

Upvotes: 0

Views: 98

Answers (3)

Steve
Steve

Reputation: 216313

You could use TakeWhile to get back only the items from the splitted list that precede the currentView.

var curView = "1002";
if (Session["breadCrumb"] != null) 
{
    var crumb = Session["breadCrumb"].ToString().Split('|').ToList();
    var viewExists = crumb.TakeWhile(c => c != curView).ToList();
    viewExists.Add(curView);
    string result = string.Join("|",viewExists);
}

While this approach works I think that also the previous answer (now wrongly deleted from Mr. Andrew Whitaker) was correct. Using IndexOf should be faster with less splitting, looping, joining strings. I suggest Mr Whitaker to undelete its answer.

EDIT
This is from the deleted answer from Mr.Whitaker.
I will repost here because I think that its approach is simpler and should give better perfomances, so future readers could see also this option.

var crumb = Session["breadCrumb"].ToString()
int index = crumb.IndexOf(curView);
if (index >= 0)
{
    Session["breadCrumb"] = crumb.Substring(0, index + curView.Length);
}

If Andrew decide to undelete its answer I will be glad to remove this part. Just let me know.

Upvotes: 3

hangy
hangy

Reputation: 10859

You could just store a List<string> in the Session directly. This saves you from having to split/concat the string manually. I know this does not answer the question directly, but I believe it is a superior solution to that.

var curView = "1002";

var crumb = Session["breadCrumb"] as List<string>;
if (crumb != null) {
    var viewExists = crumb.Any(c => c.Value == curView);

    if (viewExists) {
        // remove everything after that item in the array.            
    }
}

Upvotes: 2

Jon
Jon

Reputation: 437554

I almost regret this, but frankly I'd just go for a regular expression:

var result = Regex.Replace(input, "(?<=(\\||^)" + current + ")(?=\\||$).*", "");

This does not directly tell you if the current view existed in the input, but even though this is also possible with the regex in this particular instance another, dead simple test exists:

var viewExists = result.Length != current.Length;

Upvotes: 1

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