CODEWITHSUNDEEP
vb.net
Bia Mada
Bia Mada

Reputation: 7

Delete specific array string in VB.Net

how can I delete all that string instead of writing nothing? because nothing actually means a line with nothing, but the line exists. I want it to no longer exist!

Dim textfile() As String = IO.File.ReadAllLines(My.Application.Info.DirectoryPath + ("\textfile.txt"))

For i As Integer = 0 To textfile.Count - 1
    If textfile(i).Length > 1 Then
        textfile(i) = Nothing 'here i want to delete
    End if
Next

Upvotes: 0

Views: 186

Answers (3)

djv
djv

Reputation: 15774

You need to filter out the empty lines, and write to a file. The accepted answer does the first part of this, so here is the complete solution

Dim textFile = File.ReadAllLines("filename.txt")
Dim fixedLines = textFile.Where(Function(line) Not String.IsNullOrWhiteSpace(line))
File.WriteAllLines("filename.txt", fixedLines)

@HansPassant pointed out in a comment that this is not the most efficient solution. Here is another way to do it using StreamReader / StreamWriter

Dim lines As New List(Of String)()
Using sr As New StreamReader("filename.txt")
    While Not sr.EndOfStream
        Dim line = sr.ReadLine()
        If Not String.IsNullOrWhiteSpace(line) Then lines.Add(line)
    End While
End Using
Using sw As New StreamWriter("filename.txt")
    For Each line In lines
        sw.WriteLine(line)
    Next
End Using

However, using a 1kb file ~1000 line file with a few empty lines, my system takes about 18ms for the first method, and 18 ms for the second (each averaged 1000 times). So at least in my system, in this case, there isn't much of a difference. See https://designingefficientsoftware.wordpress.com/2011/03/03/efficient-file-io-from-csharp/ for further analysis if efficiency is a concern.

Upvotes: 2

T.S.
T.S.

Reputation: 19340

According to this If textfile(i).Length > 1 Then you seem want only short lines to remain. And you setting nothing only to long ones

Do this using LINQ

Dim onlyShortLines() as String = 
   textfile.Where(Func(x) x.Length = 1).Select(Func(x) x).ToArray()

Upvotes: -1

David
David

Reputation: 6111

You can use LINQ to select only lines that are not empty:

Dim textfile = IO.File.ReadAllLines(IO.Path.Combine(My.Application.Info.DirectoryPath, "textfile.txt"))
Dim filteredTextFile = textfile.Where(Function(line) Not String.IsNullOrWhitespace(line)).ToArray()

Fiddle: https://dotnetfiddle.net/nUpjEH

Upvotes: 3

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