[RESOLVED] [2008] Need help with StreamReader

[tassa]

I'm trying to read a *.txt file and see if it has anything written on it. This is my code:

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
            Dim line As String = Nothing
            Dim reader As New IO.StreamReader("C:\text.txt")
            line = reader.ReadLine()
            If line = Nothing Then
                MsgBox("There are no text!", MsgBoxStyle.Exclamation, "Error")
            End If
End Sub

But when i use it doesn't pop the MsgBox. What's wrong with it?

[NickThissen]

Just a guess here but it might be that the ReadLine() method returns an empty string (String.Empty, or "") instead of Nothing when there is no text. So you should check if line = String.Empty or line = "" (one of these two, not both).

In your current code, line is never Nothing. It is either an empty string or a non-empty string (the text in the file).

[tassa]

I tried that, still nothing happens

[NickThissen]

Worked just fine here... Are you sure your txt file is empty? It doesn't contain a space or some invisible character?

I also tried it like this, and it works fine:

Dim txt As String
        Dim r As New IO.StreamReader("C:\text.txt")
        txt = r.ReadToEnd()
 
        If txt = String.Empty Then
            MsgBox("No text...")
        End If
 
        r.Close()

Also, don't forget to Close your StreamReader object otherwise your file will remain locked!

[Atheist]

What, exactly, does 'line' equal to when it reaches the IF-statement?
And more importantly, what does the textfile contain?

[mendhak]

If .Peek() > 0, then there's something in there and you can do a ReadLine.

[tassa]

@Atheist:

The text file contains a bunch of names, that are the items of a listbox. I just want check it, to see if its empty or if it has names in it.

[jmcilhinney]

What the frog is saying is that there's no need to actually read anything if all you want to know is whether there is data or not. You simply open the StreamReader and call Peek to see whether there's data or not. The EndOfStream property will do the same thing.

That said, there's no point even opening the file if all you want to know is whether it contains data or not.

If New IO.FileInfo("file path here").Length > 0 Then
    'There is data.
End If

[tassa]

Doesn't work for me. Is there a way to find out if a listbox has no items? I tried:

If ListBox.Items.Count = 0 Then
'Something
End If

But that doesn't work, because the starting index = 0. So, is there any other ways?

EDIT: Nvm, got it working.

[jmcilhinney]

Doesn't work for me.

We're not pulling your leg here. We're making these suggestions because we know they work. No offence but, if they don't work for you, it's because you're implementing them wrong. If you don't show us what you tried then we can't tell you what you did wrong.

Is there a way to find out if a listbox has no items? I tried:

If ListBox.Items.Count = 0 Then
'Something
End If

But that doesn't work, because the starting index = 0. So, is there any other ways?

That IS the way and it DOES work. The index of the last item is always 1 less than the Count. If there was 1 item its index would be 0 and the Count would be 1. If the Count is 0 then there are no items. This supports the theory that you just didn't implement the other ideas we suggested properly. I'm telling you for a fact that if you do this:

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
            If New IO.FileInfo("C:\text.txt").Length = 0 Then
                MsgBox("There is no text!", MsgBoxStyle.Exclamation, "Error")
            End If
End Sub

then it will do what you've told us you want to do. If it doesn't do what you ACTUALLY want to do then you have misinformed us.

[tassa]

That's why i edited the post, because it worked for me. I didn't post another one to prevent double post or spam. But it worked!

So... Thanks!

[jmcilhinney]

That's why i edited the post, because it worked for me. I didn't post another one to prevent double post or spam. But it worked!

So... Thanks!

It wouldn't have been a double post or spam to post new information. It's generally not a good idea to edit existing posts unless it's to correct something, which I guess that this case could be construed as. I was already viewing your post before the edit so I didn't see it. Anyway, all's well that ends well.

[tassa]

I used that code. Thanks everyone for your help!

If New IO.FileInfo(My.Settings.CurrentDirectory & "List.txt").Length = 0 Then
            If ListBox1.Items.Count >= 1 Then
                Dim printFont As New System.Drawing.Font("Tahoma", 12, System.Drawing.FontStyle.Regular)
                Dim writer As New IO.StreamWriter(My.Settings.CurrentDirectory & "List.txt")
                For i As Integer = 0 To ListBox1.Items.Count - 1
                    writer.WriteLine(ListBox1.Items.Item(i))
                Next
                writer.Close()
                statusClose = False
                Me.Close()
            Else
                MsgBox("There is no text!", MsgBoxStyle.Exclamation, "Error!")
            End If
        End If

[jmcilhinney]

There are a few minor improvements I'd make to that:

Dim filePath As String = IO.Path.Combine(My.Settings.CurrentDirectory, "List.txt")
 
If New IO.FileInfo(filePath).Length = 0 Then
    If ListBox1.Items.Count = 0 Then
        MessageBox.Show("There is no text!", "Error!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
    Else
        Using writer As New IO.StreamWriter(filePath)
            For Each item As String In ListBox1.Items
                writer.WriteLine(item)
            Next
        End Using
 
        statusClose = False
        Me.Close()
    End If
End If

[tassa]

What is the Path.Combine for?

Edit: I just understood how it works. Thanks for the improvement!

[jmcilhinney]

What is the Path.Combine for?

This is the best way to learn. If you see a type or member you're not familiar with you go immediately to the documentation for that type or member and you read about it. I cannot tell you how many times that has provided me with the answer to my question and more besides.