CODEWITHSUNDEEP
c#
fs_tigre
fs_tigre

Reputation: 10738

Find index of number if item exists in ObservableCollection in C#/WPF

In the following code I'm checking if a certain item exists in an ObservableCollection and if it does, I want to grab its index so I can move that item to the top but I cannot figure it out.

My object:

public class RecentFile
{
    public string FileName { get; set; }
    public string DateAdded { get; set; }
}

Cod for finding index of item: 

if (recentFilesObservableCollection.Any(f => f.FileName == "MyFileName")) {

    foreach (RecentFile file in recentFilesObservableCollection) {
        if (file.FileName == "MyFileName") {
            var x = RecentFilesDataGrid[(recentFilesObservableCollection.IndexOf(file)];
        }
    }
}

What would be the best way to get the index number if the item exists?

Ultimately what I need to do is...

  1. Check if item exists
  2. If it does move it to the top of the list

Upvotes: 1

Views: 4150

Answers (3)

Eliahu Aaron
Eliahu Aaron

Reputation: 4552

You can create extension methods similar to List<T>.FindIndex(...) methods:

public static class ObservableCollectionExtensions
{
    public static int FindIndex<T>(this ObservableCollection<T> ts, Predicate<T> match)
    {
        return ts.FindIndex(0, ts.Count, match);
    }

    public static int FindIndex<T>(this ObservableCollection<T> ts, int startIndex, Predicate<T> match)
    {
        return ts.FindIndex(startIndex, ts.Count, match);
    }

    public static int FindIndex<T>(this ObservableCollection<T> ts, int startIndex, int count, Predicate<T> match)
    {
        if (startIndex < 0) startIndex = 0;
        if (count > ts.Count) count = ts.Count;

        for (int i = startIndex; i < count; i++)
        {
            if (match(ts[i])) return i;
        }

        return -1;
    }
}

Usage:

int index = recentFilesObservableCollection.FindIndex(f => f.FileName == "MyFileName");
if (index > 0)
{
    // Move it to the top of the list
    recentFilesObservableCollection.Move(index, 0);
}

Upvotes: 0

bginsburg
bginsburg

Reputation: 123

Try this: Int index=YourCollection.IndexOf(x => x.fileName == “name”); And then use MoveItem which takes current index and destination index.

Upvotes: 0

Nkosi
Nkosi

Reputation: 247153

Check if item exists. If it does get the item to find its index. From there move it.

//Check if item exists
if (recentFilesObservableCollection.Any(f => f.FileName == "MyFileName")) {
    //If it does, get item
    var file = recentFilesObservableCollection.First(f => f.FileName == "MyFileName");
    //grab its index
    var index = recentFilesObservableCollection.IndexOf(file);
    if (index > 0)
        //move it to the top of the list
        recentFilesObservableCollection.Move(index, 0);
}

Another alternative that achieves the same result with less enumerations.

var item = recentFilesObservableCollection
    .Select((file, index) => new { file, index })
    .FirstOrDefault(f => f.file.FileName == "MyFileName"));
if(item != null && item.index > 0) // or if(item?.index > 0)
    recentFilesObservableCollection.Move(item.index, 0);

Upvotes: 4

Related Questions