Use LINQ to move item to top of list

user_3193 0
Viewed 79461

Is there a way to move an item of say id=10 as the first item in a list using LINQ?

Item A - id =5
Item B - id = 10
Item C - id =12
Item D - id =1

In this case how can I elegantly move Item C to the top of my List<T> collection?

This is the best I have right now:

var allCountries = repository.GetCountries();
var topitem = allCountries.Single(x => x.id == 592);  
var finalList = new List<Country>();
finalList.Add(topitem);
finalList = finalList.Concat(allCountries.Where(x=> x.id != 592)).ToList();
sorting linq c#
12 Answers

Its interesting the number of approaches you find when trying to solve a problem. 

var service = AutogateProcessorService.GetInstance();
var allConfigs = service.GetAll();
allConfigs = allConfigs.OrderBy(c => c.ThreadDescription).ToList();
var systemQueue = allConfigs.First(c => c.AcquirerId == 0);
allConfigs.Remove(systemQueue);
allConfigs.Insert(0, systemQueue);
user_26327430

Even easier if you have the object:

listOfObjects.Remove(object);
listOfObjects.Insert(0, object);
user_154109160

I wrote a static extension method to do this. Note this doesn't preserve the order, it simply swaps the item out. If you needed to preserve the order you should do a rotate not a simple swap.

/// <summary>
/// Moves the item to the front of the list if it exists, if it does not it returns false
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="collection"></param>
/// <param name="predicate"></param>
/// <returns></returns>
public static bool MoveToFrontOfListWhere<T>(this List<T> collection, Func<T, bool> predicate)
{
    if (collection == null || collection.Count <= 0) return false;

    int index = -1;
    for (int i = 0; i < collection.Count; i++)
    {
        T element = collection.ElementAt(i);
        if (!predicate(element)) continue;
        index = i;
        break;
    }

    if (index == -1) return false;

    T item = collection[index];
    collection[index] = collection[0];
    collection[0] = item;
    return true;
}
user_4345370
Related