Comment by AshamedCaptain

>to claim "the language doesn't allow simple things such as checking for a file's existence" (which is false,

That's not what I wrote. I said there's no _built-in_ way to check existence of the file. A reasonable interpretation of "built-in" is for an obvious named function such as "File.exists()" _without_ cobbling together extra workarounds and hacks -- whether those workarounds include re-purposing other VB built-in functions with On Error ... or using Win32 interop.

> in VB, [...] would at worse be comprised of a exception handler (on error ...)

That's an example of what I meant of not being built-in to VB. I should have been more clear. We were using different meanings of "builtin".

In any case, the following "pure" VB code to check for file existence is not found on Google or Bing search but I still have it from my 1995 archives and copied it here. It has many lines of code (instead of a simple "one-liner") because it tries to cover all the edge cases. And yet with all that defensive code, there's still a hidden timebomb of a bug in it. Can anyone spot it? The code is unmodified from Visual Basic Programmer's Journal. In contrast, the alternative using Win32 interop with OF_EXISTS doesn't have the bug.

  Dim strTestFilename As String
  strFilename = Trim(strFilename)

  ' To avoid problem with known bug, don't pass root directory to
  ' the Name function
    Select Case Right$(strFilename, 1)
        Case "\": strExistsFilename = "Root": Exit Function
        Case "\.": strExistsFilename = "Root": Exit Function
        Case "\..": strExistsFilename = "Root": Exit Function
    End Select

    On Local Error Resume Next      ' Enable error trapping for Name function
    Name strFilename As strFilename ' A trick to see if filename/path is good

  ' Now check the resulting err code of the Name function
    Select Case Err
        Case 5  ' Illegal function call
        Case 53 ' File not found
        Case 58         ' File exists (maybe)
            strTestFilename = Dir$(strFilename)
            If Len(strTestFilename) Then
                strExistsFilename = ""      ' It's a file
            Exit Function
            Else
                strExistsFilename = "Dir"   ' It's a directory
                Exit Function
            End If
        Case 64 ' Bad filename
        Case 68 ' Device unavailable
        Case 71 ' Disk not ready
        Case 75 ' Access denied
        Case 76 ' Path not found
    End Select

My point was that C# builtin File.Exists() is a lot simpler than that.

It better not!

If you actually open a file, you update it's access time, and you interfere with the process that should actually open the file. Those both break perfectly simple business logic.

You don't use exists and then open a file. If you actually want to open a file, you open it or fail. You don't check if it's ok and then do it, you do it and then check if it failed.

exists followed by open is a pointless exists because anything can happen in between.

Conversely, if you are neither the producer nor consumer of the file at this time, you don't want to actually open it just as a way to stat it, because actually opening it updates it's access time and interferes with the actual consumer(s). Even read-only non-exclusive.