Concat strings by & and + in VB.Net

Question

Is there any difference between & and + operators while concatenating string? if yes, then what is difference? And if No, then why below code generating exception?

Answer 1

& and + are both concatenation operators but when you specify an integer while using +, vb.net tries to cast "Hello" into integer to do an addition. If you change "Hello" with "123", you will get the result 124.

Answer 2

You've probably got Option Strict turned on (which is a good thing), and the compiler is telling you that you can't add a string and an int. Try this:

t = s1 & i.ToString()

Answer 3

My 2 cents:

If you are concatenating a significant amount of strings, you should be using the StringBuilder instead. IMO it's cleaner, and significantly faster.

Answer 4

Try this. It almost seemed to simple to be right. Simply convert the Integer to a string. Then you can use the method below or concatenate.

Dim I, J, K, L As Integer
Dim K1, L1 As String

K1 = K
L1 = L
Cells(2, 1) = K1 & " - uploaded"
Cells(3, 1) = L1 & " - expanded"

MsgBox "records uploaded " & K & " records expanded " & L

Answer 5

As your question confirms, they are different: & is ONLY string concatenation, + is overloaded with both normal addition and concatenation.

In your example:

• because one of the operands to + is an integer VB attempts to convert the string to a integer, and as your string is not numeric it throws; and

• & only works with strings so the integer is converted to a string.

Answer 6

From a former string concatenater (sp?) you should really consider using String.Format instead of concatenation.

    Dim s1 As String
    Dim i As Integer
    s1 = "Hello"
    i = 1
    String.Format("{0} {1}", s1, i)

It makes things a lot easier to read and maintain and I believe makes your code look more professional. See: code better – use string.format. Although not everyone agrees When is it better to use String.Format vs string concatenation?