CODEWITHSUNDEEP
vb.net
Daniel
Daniel

Reputation: 11

Visual Basic - StreamWriter - How to skip to next line IF said line isn't empty

Hey so I'm trying to do a simple StreamWriter for adding staff information to a text file (I already have a working StreamReader log in page) , the text file has some sample data but also must be able to have new data written to it.

My problem is that ONLY upon initial start up and my initial writing of data the information is written on the same line as the last line of sample data in the text file, not on the next blank line. Here is how the text file looks after the first attempt to write data after start up.

"Me,Too" being my last line of sample data and "Grey,Hardy" being my first data written via StreamWriter

I've done some research on here and found examples of how to write a blank line which you could make the StreamWriter do every time to put spacing in between etc. but that doesn't work here as this problem only occurs the first time on any given start up and if it left a blank line every single time then if I made two attempts to use the StreamWriter it would look like

Which would then enable a blank log in to work.

Here is my code for the StreamWriter

'StreamReader to check if a line is empty or not
        Dim StaffReader As StreamReader = File.OpenText("StaffInfo.txt")
        strLine = StaffReader.ReadLine()
        StaffReader.Close()
        'Streamwriter for adding staff log in to textfile
        Dim FileCheck As StreamWriter = File.AppendText("StaffInfo.txt")
        FileCheck.WriteLine(strStaffUsername2 & "," & strStaffPass2)
                FileCheck.Close(``)
                MessageBox.Show(strStaffUsername2 & " added to the file. ", "Data Added")
                txtUser2.Clear()
                txtUser2.Focus()
                txtPass2.Clear()

I just want it to skip to the next blank line if the line it is going to write on has any characters on it.

Upvotes: 1

Views: 1003

Answers (2)

Code Pope
Code Pope

Reputation: 5449

what you are looking for is the point, if the last line in your file contains a carriage return or not. If it does contain a carriage return, then you can append your text with your written code. But if it does not contain a carriage return, you have to prefix your first line with a carriage return.
Thus, first you have to check if your last line has a carriage return. You can do that by a function like this: 

Private Function DoesLastLineHasCarriagReturn(Filename As String) As Boolean
    Dim s as String = ""
    using stream = New StreamReader(Filename)
        ' we have to read the last two characters
        stream.BaseStream.Seek(-2,SeekOrigin.End)
        dim c_beforeLast as Integer = stream.Read()
        Dim c_Last As Integer = stream.Read()
        ' if the last character is 10 -> we have a carriage return. Windows and Linux just use different encodings
        if (c_Last =10)
            If(c_beforeLast = 13)
                Console.WriteLine("Ends with carriage return CRLF (Windows)")
            Else 
                Console.WriteLine("Ends with carriage return LF (UNIX, OSX )")
            End If
            return true
        Else 
            Console.WriteLine("Does not end with Carriage return")     
        End If
    End Using
    return false      
End Function

Then when beginning to write in the file, first you have to call the function. Here how your code could look like:

If DoesLastLineHasCarriagReturn("StaffInfo.txt")
    Dim FileCheck As StreamWriter = File.AppendText("StaffInfo.txt")
   FileCheck.WriteLine("Greg" & "," & "Hardy")
   FileCheck.Close()
Else 
    Dim FileCheck As StreamWriter = File.AppendText("StaffInfo.txt")
    FileCheck.WriteLine(vbCrLf + "Greg" & "," & "Hardy")
    FileCheck.Close()
End If

By the way, I would recommend you to use the using statement to close the stream automatically:

If DoesLastLineHasCarriagReturn("StaffInfo.txt")
    Using writer As New StreamWriter("StaffInfo.txt", True)
        writer.WriteLine("Greg" & "," & "Hardy")
    End Using
Else 
    Using writer As New StreamWriter("StaffInfo.txt", True)
        writer.WriteLine(vbCrLf +"Greg" & "," & "Hardy")
    End Using
End If

Upvotes: 1

Mary
Mary

Reputation: 15091

Since we are dealing with a text file and not doing anything fancy, we can just use the File class in System.IO.

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim FilePath = "TestFiles/File1.txt"
    'Dump contents of file
    Dim fileContents As String = File.ReadAllText(FilePath)
    'Extract the last 2 characters in the contents
    Dim NextToLast As String = fileContents(fileContents.Length - 2)
    Dim LastCharacter As String = fileContents(fileContents.Length - 1)
    'Check if we have a CrLf an if not add a new line
    If Not NextToLast = Chr(13) AndAlso Not LastCharacter = Chr(10) Then
        File.WriteAllText(FilePath, Environment.NewLine)
    End If
    'Write to the file
    File.AppendAllLines(FilePath, {TextBox1.Text})
End Sub

To display your text file, add a ListBox to your form.

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    'Put the contents of the file into a string array of lines
    Dim staff() As String = File.ReadAllLines("TestFiles/File1.txt")
    ListBox1.DataSource = staff
End Sub

Upvotes: 0

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