Remove Where in ICollection - CSharp System.Collections

CSharp examples for System.Collections:ICollection

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Description

Remove Where in ICollection

Demo Code


using System.Collections.Generic;
using System.Collections;
using System;/* w  ww .  ja  va2 s .  c o  m*/

public class Main{
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1800:DoNotCastUnnecessarily")]
        internal static ICollection<T> RemoveWhere<T>(ICollection<T> collection, Predicate<T> predicate)
        {
            if (collection == null)
                throw new ArgumentNullException("collection");
            if (predicate == null)
                throw new ArgumentNullException("predicate");
          

            IList<T> list = collection as IList<T>;
            if (list != null) {
                T item;
                int i = -1, j = 0;
                int listCount = list.Count;
                List<T> removed = new List<T>();

                // Remove item where predicate is true, compressing items to lower in the list. This is much more
                // efficient than the naive algorithm that uses IList<T>.Remove().
                while (j < listCount) {
                    item = list[j];
                    if (predicate(item)) {
                        removed.Add(item);
                    }
                    else {
                        ++i;
                        if (i != j)
                            list[i] = item;
                    }
                    ++j;
                }

                ++i;
                if (i < listCount) {
                    // remove items from the end.
                    if (list is IList && ((IList)list).IsFixedSize) {
                        // An array or similar. Null out the last elements.
                        while (i < listCount)
                            list[i++] = default(T);
                    }
                    else {
                        // Normal list.
                        while (i < listCount) {
                            list.RemoveAt(listCount - 1);
                            --listCount;
                        }
                    }
                }

                return removed;
            }
            else {
                // We have to copy all the items to remove to a List, because collections can't be modifed 
                // during an enumeration.
                List<T> removed = new List<T>();

                foreach (T item in collection)
                    if (predicate(item))
                        removed.Add(item);

                foreach (T item in removed)
                    collection.Remove(item);

                return removed;
            }
        }
}

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