C# | How to insert the elements of a collection into the List at the specified index - GeeksforGeeks

18 Oct, 2019
List<T>.InsertRange(Int32, IEnumerable<T>) Method is used to insert the elements of a collection into the List<T> at the specified index.
Properties of List:
It is different from the arrays. A list can be resized dynamically but arrays cannot.
List class can accept null as a valid value for reference types and it also allows duplicate elements.
If the Count becomes equals to Capacity then the capacity of the List increases automatically by reallocating the internal array. The existing elements will be copied to the new array before the addition of the new element.
Syntax:
public void InsertRange (int index, System.Collections.Generic.IEnumerable<T> collection);

Parameter:
index: It is the zero-based index at which the new elements should be inserted.
collection: It is the collection whose elements will be inserted into the List<T>
Note: The collection itself cannot be null. But it can contain elements which can be null if the type T is a reference type.
Exceptions:
ArgumentNullException: If the collection is null.
ArgumentOutOfRangeException: If the index is less than zero or greater than count.
Below programs illustrate the use of above discussed method:
Example 1:
// C# Program to insert the elements of// a collection into the List<T> at the// specified indexusing System;using System.Collections;using System.Collections.Generic;  class Geeks {      // Main Method    public static void Main(String[] args)    {          string[] str1 = { "Geeks",                          "for",                          "Geeks" };          // Creating an List<T> of strings        // adding str1 elements to List        List<String> firstlist = new List<String>(str1);          // displaying the elements of firstlist        Console.WriteLine("Elements in List: \n");          foreach(string dis in firstlist)        {            Console.WriteLine(dis);        }          Console.WriteLine(" ");          // contains new Elements which is        // to be added in the List        str1 = new string[] { "New",                              "Element",                              "Added" };          // using InsertRange Method        Console.WriteLine("InsertRange(2, str1)\n");          // adding elements after 2nd        // index of the List        firstlist.InsertRange(2, str1);          // displaying the elements of        // List after InsertRange Method        foreach(string res in firstlist)        {            Console.WriteLine(res);        }    }}
Output:
Elements in List: 

Geeks
for
Geeks
 
InsertRange(2, str1)

Geeks
for
New
Element
Added
Geeks

Example 2:
// C# Program to insert the elements of// a collection into the List<T> at the// specified indexusing System;using System.Collections;using System.Collections.Generic;  class Geeks {      // Main Method    public static void Main(String[] args)    {          string[] str1 = { "Geeks",                          "for",                          "Geeks" };          // Creating an List<T> of strings        // adding str1 elements to List        List<String> firstlist = new List<String>(str1);          // displaying the elements of firstlist        Console.WriteLine("Elements in List: \n");          foreach(string dis in firstlist)        {            Console.WriteLine(dis);        }          Console.WriteLine(" ");          // contains new Elements which is        // to be added in the List        str1 = new string[] { "New",                              "Element",                              "Added" };          // using InsertRange Method        Console.WriteLine("InsertRange(2, str1)\n");          // this will give error as        // index is less than 0        firstlist.InsertRange(-1, str1);          // displaying the elements of        // List after InsertRange Method        foreach(string res in firstlist)        {            Console.WriteLine(res);        }    }}
Error:
Unhandled Exception:System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.Parameter name: index
Reference:
https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1.insertrange?view=netframework-4.7.2
nidhi_biet
CSharp-Collections-Namespace
CSharp-Generic-List
CSharp-Generic-Namespace
CSharp-method
C#
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
C# | Delegates
C# | Abstract Classes
Difference between Ref and Out keywords in C#
Extension Method in C#
C# | Class and Object
C# | Replace() Method
C# | Constructors
Introduction to .NET Framework
C# | Data Types
HashSet in C# with Examples