VS 2012: N00bie - Reading/writing an array from txt file?

[tedski_69]

New to all this so bear with me. Haven't done any serious programming since the days of the spectrum zx81.

I have a file "numbers.txt" which looks like this...

0 1 4
2 6 3

I want to read this file into my app as...

a(0)=0, a(1)=1... a(5)=3

Also how would I do the reverse. i.e. write an array to file?

Thanks

[jmcilhinney]

Are there always going to be six numbers in the file? If not, will you always know the numbers of values ahead of time? Are you always going to want to write the data to the same number of lines? You've given us an example but not told us what the rules are.

[tedski_69]

Yes I will know how many numbers in advance.

A lot more than in the example. I am merely using 6 here and will expand when I write.

[jmcilhinney]

You answered my first question and your answer to that made my second question moot. Are you planning on answering my third question any time soon?

[tedski_69]

Didn't realise it was this complicated.

I am going to need to read and write groups of numbers. Sometimes 5x5, 6x6, 7x7... 24x24 etc. Sometimes a few columns sometimes a lot.

[jmcilhinney]

Didn't realise it was this complicated.

You can't give a computer vague instructions. You have to tell it EXACTLY what to do. If we're going to tell you exactly what to tell the computer then we need to know exactly what you want it to do, not just one example with no idea in which direction to extrapolate.

I am going to need to read and write groups of numbers. Sometimes 5x5, 6x6, 7x7... 24x24 etc. Sometimes a few columns sometimes a lot.

Would it not be more appropriate to use a 2D array given that your data seems to be stored in that format?

[tedski_69]

Agreed 2D would be better.

[jmcilhinney]

E.g.

Private Function ReadMatrixFromFile(rowCount As Integer, columnCount As Integer, filePath As String) As Integer(,)
    Dim matrix(rowCount, columnCount) As Integer
 
    Using reader As New StreamReader(filePath)
        For rowIndex = 0 To matrix.GetUpperBound(0)
            'Read a line and split it on the spaces.
            Dim values = reader.ReadLine().Split()
 
            For columnIndex = 0 To matrix.GetUpperBound(1)
                matrix(rowIndex, columnIndex) = CInt(values(columnIndex))
            Next
        Next
    End Using
 
    Return matrix
End Function
 
Private Sub WriteMatrixToFile(matrix As Integer(,), filePath As String)
    Using writer As New StreamWriter(filePath)
        For rowIndex = 0 To matrix.GetUpperBound(0)
            'Write a line break before all but the first line.
            If rowIndex > 0 Then
                writer.WriteLine()
            End If
 
            For columnIndex = 0 To matrix.GetUpperBound(1)
                'Write a space before all but the first value.
                If columnIndex > 0 Then
                    writer.Write(" ")
                End If
 
                writer.Write(matrix(rowIndex, columnIndex).ToString())
            Next
        Next
    End Using
End Sub

That code has no error handling, which should be at the level above.

[annaharris]

Do you want to accomplish it using dynamc array or static array ?

[Niya]

Do you want to accomplish it using dynamc array or static array ?

In the truest sense, all arrays in .Net are static. Dynamic arrays are only a trick and a performance costly one at that. If one needs dynamic arrays, then one should be using a Collection(Of T) or a List(Of T) instead.

[tedski_69]

Cheers guys thanks. I'll give this a whirl.