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?
Example:
Dim s, s1, t As String
Dim i As Integer
s1 = "Hello"
i = 1
s = s1 & i
t = s1 + i //Exception here
If s = t Then
MessageBox.Show("Equal...")
End If
& 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.
& is only used for string concatenation. + is overloaded to do both string concatenation and arithmetic addition.The double purpose of + leads to confusion, exactly like that in your question. Especially when Option Strict is Off, because the compiler will add implicit casts on your strings and integers to try to make sense of your code.
My recommendations
Option Strict On, then the compiler will force you to add explicit casts where it thinks they are necessary. + for concatenation because of the ambiguity with arithmetic addition. Both these recommendations are also in the Microsoft Press book Practical Guidelines And Best Practises for VB and C# (sections 1.16, 21.2)
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()
s = s1 & i. Error 1 Option Strict On disallows implicit conversions from 'String' to 'Double'.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.
You can write '&' to add string and integer :
processDetails=objProcess.ProcessId & ":" & objProcess.name
message = msgbox(processDetails,16,"Details")
output will be:
5577:wscript.exe
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
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?
String.Format. Any advice to always use one over the other is wrong, and this is no exception. Take advantage of compiler optimizations. This idea of doing something to "make your code look more professional" is stupid. That's the kind of thing that justifies using C++ when your task is made much easier with a dynamic scripting language because oh, that just look too "unprofessional". Professional software is stuff that works...well. Appearance is irrelevant. The answers in the question you linked appear to confirm this.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.
StringBuilder is not going to help in this case. When you're dealing with less than (approximately) 4 appends, the overhead of StringBuilder is generally not worth it. The asker isn't appending strings in a loop, so there's no point. Before making recommendations, understand what the things you're recommending actually do and how they work. Ditch the cargo-cult programming routine.
+was even a concatenation operator in VB. That's one of the things I hate about JavaScript is that+is for concat and addition.&concatenation operator is one of the things I love about VB. And if you're using+when there's an alternative available, that's not the language's fault, it's your fault as a programmer for not knowing the language.+doubles as a concatenation operator in some languages, and I used JavaScript as an example, as that's where I deal with it the most. I completely agree, I love the fact that&is a separate concat operator in VB, and that's all I knew even existed as a concat operator in VB until now. VB is my primary language for desktop applications.