C# | Insert an element into Collection<T> at specified index

Collection<T>.Insert(Int32, T) method is used to insert an element into the Collection<T> at the specified index. Syntax:

public void Insert (int index, T item);

Parameters:

index : The zero-based index at which item should be inserted. item : The object to insert. The value can be null for reference types.

Exception: This method will give ArgumentOutOfRangeException if index is less than zero OR index is greater than Count. Below given are some examples to understand the implementation in a better way: Example 1: Output:

Count : 5
A
B
C
D
E
Count : 6
A
B
GFG
C
D
E

Example 2:

Runtime Error:

Unhandled Exception: System.ArgumentOutOfRangeException: Index must be within the bounds of the List. Parameter name: index

Note:

• Collection<T> accepts null as a valid value for reference types and allows duplicate elements.
• If index is equal to Count, item is added to the end of Collection<T>.
• This method is an O(n) operation, where n is Count.

Reference:

• https://learn.microsoft.com/en-us/dotnet/api/system.collections.objectmodel.collection-1.insert?view=netframework-4.7.2