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Collection<T>.Remove Method

Removes the first occurrence of a specific object from the Collection<T>.

Namespace:  System.Collections.ObjectModel
Assembly:  mscorlib (in mscorlib.dll)

public bool Remove(
	T item
)

Parameters

item
Type: T

The object to remove from the Collection<T>. The value can be null for reference types.

Return Value

Type: System.Boolean
true if item is successfully removed; otherwise, false. This method also returns false if item was not found in the original Collection<T>.

Implements

ICollection<T>.Remove(T)

This method determines equality using the default equality comparer EqualityComparer<T>.Default for T, the type of values in the list.

This method performs a linear search; therefore, the average execution time is proportional to Count. That is, this method is an O(n) operation, where n is Count.

Notes to Inheritors

Derived classes can override RemoveItem to change the behavior of this method.

The following code example demonstrates many of the properties and methods of Collection<T>. The code example creates a collection of strings, uses the Add method to add several strings, displays the Count, and lists the strings. The example uses the IndexOf method to find the index of a string and the Contains method to determine whether a string is in the collection. The example inserts a string using the Insert method and retrieves and sets strings using the default Item property (the indexer in C#). The example removes strings by string identity using the Remove method and by index using the RemoveAt method. Finally, the Clear method is used to clear all strings from the collection.

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

public class Demo
{
    public static void Main()
    {
        Collection<string> dinosaurs = new Collection<string>();

        dinosaurs.Add("Psitticosaurus");
        dinosaurs.Add("Caudipteryx");
        dinosaurs.Add("Compsognathus");
        dinosaurs.Add("Muttaburrasaurus");

        Console.WriteLine("{0} dinosaurs:", dinosaurs.Count);
        Display(dinosaurs);

        Console.WriteLine("\nIndexOf(\"Muttaburrasaurus\"): {0}", 
            dinosaurs.IndexOf("Muttaburrasaurus"));

        Console.WriteLine("\nContains(\"Caudipteryx\"): {0}", 
            dinosaurs.Contains("Caudipteryx"));

        Console.WriteLine("\nInsert(2, \"Nanotyrannus\")");
        dinosaurs.Insert(2, "Nanotyrannus");
        Display(dinosaurs);

        Console.WriteLine("\ndinosaurs[2]: {0}", dinosaurs[2]);

        Console.WriteLine("\ndinosaurs[2] = \"Microraptor\"");
        dinosaurs[2] = "Microraptor";
        Display(dinosaurs);

        Console.WriteLine("\nRemove(\"Microraptor\")");
        dinosaurs.Remove("Microraptor");
        Display(dinosaurs);

        Console.WriteLine("\nRemoveAt(0)");
        dinosaurs.RemoveAt(0);
        Display(dinosaurs);

        Console.WriteLine("\ndinosaurs.Clear()");
        dinosaurs.Clear();
        Console.WriteLine("Count: {0}", dinosaurs.Count);
    }

    private static void Display(Collection<string> cs)
    {
        Console.WriteLine();
        foreach( string item in cs )
        {
            Console.WriteLine(item);
        }
    }
}

/* This code example produces the following output:

4 dinosaurs:

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

IndexOf("Muttaburrasaurus"): 3

Contains("Caudipteryx"): True

Insert(2, "Nanotyrannus")

Psitticosaurus
Caudipteryx
Nanotyrannus
Compsognathus
Muttaburrasaurus

dinosaurs[2]: Nanotyrannus

dinosaurs[2] = "Microraptor"

Psitticosaurus
Caudipteryx
Microraptor
Compsognathus
Muttaburrasaurus

Remove("Microraptor")

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

RemoveAt(0)

Caudipteryx
Compsognathus
Muttaburrasaurus

dinosaurs.Clear()
Count: 0
 */

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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