List<T>.Insert Method
Inserts an element into the List<T> at the specified index.
Namespace: System.Collections.Generic
Assembly: mscorlib (in mscorlib.dll)
Parameters
- index
- Type: System.Int32
The zero-based index at which item should be inserted.
- item
- Type: T
The object to insert. The value can be null for reference types.
Implements
IList<T>.Insert(Int32, T)| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | index is less than 0. -or- index is greater than Count. |
List<T> accepts null as a valid value for reference types and allows duplicate elements.
If Count already equals Capacity, the capacity of the List<T> is increased by automatically reallocating the internal array, and the existing elements are copied to the new array before the new element is added.
If index is equal to Count, item is added to the end of List<T>.
This method is an O(n) operation, where n is Count.
The following code example demonstrates the Insert method, along with various other properties and methods of the List<T> generic class. After the list is created, elements are added. The Insert method is used to insert an item into the middle of the list. The item inserted is a duplicate, which is later removed using the Remove method.
using System; using System.Collections.Generic; public class Example { public static void Main() { List<string> dinosaurs = new List<string>(); Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity); dinosaurs.Add("Tyrannosaurus"); dinosaurs.Add("Amargasaurus"); dinosaurs.Add("Mamenchisaurus"); dinosaurs.Add("Deinonychus"); dinosaurs.Add("Compsognathus"); Console.WriteLine(); foreach(string dinosaur in dinosaurs) { Console.WriteLine(dinosaur); } Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity); Console.WriteLine("Count: {0}", dinosaurs.Count); Console.WriteLine("\nContains(\"Deinonychus\"): {0}", dinosaurs.Contains("Deinonychus")); Console.WriteLine("\nInsert(2, \"Compsognathus\")"); dinosaurs.Insert(2, "Compsognathus"); Console.WriteLine(); foreach(string dinosaur in dinosaurs) { Console.WriteLine(dinosaur); } Console.WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]); Console.WriteLine("\nRemove(\"Compsognathus\")"); dinosaurs.Remove("Compsognathus"); Console.WriteLine(); foreach(string dinosaur in dinosaurs) { Console.WriteLine(dinosaur); } dinosaurs.TrimExcess(); Console.WriteLine("\nTrimExcess()"); Console.WriteLine("Capacity: {0}", dinosaurs.Capacity); Console.WriteLine("Count: {0}", dinosaurs.Count); dinosaurs.Clear(); Console.WriteLine("\nClear()"); Console.WriteLine("Capacity: {0}", dinosaurs.Capacity); Console.WriteLine("Count: {0}", dinosaurs.Count); } } /* This code example produces the following output: Capacity: 0 Tyrannosaurus Amargasaurus Mamenchisaurus Deinonychus Compsognathus Capacity: 8 Count: 5 Contains("Deinonychus"): True Insert(2, "Compsognathus") Tyrannosaurus Amargasaurus Compsognathus Mamenchisaurus Deinonychus Compsognathus dinosaurs[3]: Mamenchisaurus Remove("Compsognathus") Tyrannosaurus Amargasaurus Mamenchisaurus Deinonychus Compsognathus TrimExcess() Capacity: 5 Count: 5 Clear() Capacity: 5 Count: 0 */
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.
