Insert

This VB.NET Function places another String somewhere inside the first String. Using the Insert function on the String type, we create a longer String.

When we call Insert, a new string is created—the existing string is not modified. Insert() also is available on StringBuilder, which does modify an underlying buffer.

Insert example

We call Insert. We must assign a variable to the result of Insert to get the updated string. A new string is created upon the managed heap.

Module Module1
    Sub Main()

        Dim value As String = "the cat"
        Console.WriteLine("INITIAL: {0}", value)

        ' Use Insert at an index.
        Dim result As String = value.Insert(4, "soft ")
        Console.WriteLine("INSERT: {0}", result)

    End Sub
End Module
INITIAL: the cat
INSERT: the soft cat

Insert, IndexOf

We can use the IndexOf function with Insert. This demonstrates how we can search for the target index before passing that value to Insert.

Module Module1
    Sub Main()

        Dim value As String = "the soft cat"
        Console.WriteLine("INITIAL: {0}", value)

        ' Use Insert with IndexOf.
        Dim index As Integer = value.IndexOf("cat")
        Dim result As String = value.Insert(index, "orange ")
        Console.WriteLine("INSERT: {0}", result)

    End Sub
End Module
INITIAL: the soft cat
INSERT: the soft orange cat

Strings are immutable. When we call Insert we must assign a variable reference to its result. Despite this possible complication, the Insert function is useful in many programs.