CODEWITHSUNDEEP
vb.netexception
barakuda28
barakuda28

Reputation: 2902

Setting value to a not-existing array item?

Please take a look at the following code:

Try
  Dim Reader As New System.IO.StreamReader(PositionsFileName)
  Do While Reader.Peek() <> -1
    Dim Positions() As String = Reader.ReadLine().Split("|")
    If (Positions(0) Is Nothing) Or (Positions(1) Is Nothing) Or (Positions(2) Is Nothing) Then
      ' something
    End If
  Loop
Catch ex As Exception
  ex.Source = Nothing
End Try

I am reading a file and expecting format something|something1|something2. I am trying to make it set "Nothing" to the array index which does not exists (the file format is broken), so that the If statement goes smoothly, but it seem I am doing it wrong. Can you give me some hints?

Upvotes: 2

Views: 202

Answers (3)

Victor Zakharov
Victor Zakharov

Reputation: 26424

If you do Split("|") and there are only 2 items (for example, something|something1), Positions(2) will not be Nothing, it will just not be there. So your code will raise an exception, something about index out of bounds of the array.

If you need Positions(2) contain Nothing in this case, you code can look like this:

Dim Positions(2) As String
Dim tmpArray() As String = Reader.ReadLine().Split("|")
For i = 0 To UBound(Positions)
  If i <= UBound(tmpArray) Then
    Positions(i) = tmpArray(i)
  Else
    Positions(i) = Nothing
  End If
Next

Upvotes: 1

Ceres
Ceres

Reputation: 3648

Just check positions.length after the split. Also, if you want to check for cases like "||Something2|Something3", the first position will be "" not Nothing. The orelse is a shortcircuit that will keep the latter condtitions from being evaulated if an earlier condition is met. 

If Positions.length < 3 OrElse Positions(0) = "" OrElse Positions(1) = "" OrElse Positions(2) = "" Then
  ' something
End If

Upvotes: 1

Enigmativity
Enigmativity

Reputation: 117037

I assume that you only have three "Somethings" per valid line. If so, try writing your Positions() assignment like this:

Dim Positions() As String = Reader _
    .ReadLine() _
    .Split("|") _
    .Concat(Enumerable.Repeat("Nothing", 3)) _
    .Take(3) _
    .ToArray()

This will ensure that you have three items every time. No need to check for nothings.

Upvotes: 1

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