Question

I want to read a specific line from an html source code.
Im storing the source into a string file and i want to read the line X.
So im using this method that i found on net

Public Shared Function ReadSpecifiedLine(file As String, lineNum As Integer) As String
    Dim contents As String = String.Empty
    Try
        Using stream As New StreamReader(file)
            contents = stream.ReadToEnd()
            Dim linesArray As String() = contents.Split(New Char() {ControlChars.Lf})

            If linesArray.Length > 1 Then
                If Not lineNum > linesArray.Length AndAlso Not lineNum < 0 Then
                    Return linesArray(lineNum)
                Else
                    Return linesArray(0)
                End If
            Else
                Return contents
            End If
        End Using
    Catch ex As Exception
        Return ex.ToString()
    End Try
End Function

For example im trying to read the 4th line and im getting this error.

System.ArgumentException: Illegal characters in path.
at System.IO.Path.CheckInvalidPathChars(String path, Boolean checkAdditional)
at System.IO.Path.GetFileName(String path)
at System.IO.StreamReader..ctor(String path, Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize, Boolean checkHost)
at System.IO.StreamReader..ctor(String path)
at WindowsApplication1.Form1.ReadSpecifiedLine(String file, Int32 lineNum) in C:\Users\Optimus\documents\visual studio 2012\Projects\WindowsApplication1\WindowsApplication1\Form1.vb:line 48

Any help would be appreciated.

Answer 1

The method you posted assumes you are passing in the file path. If you want to change it to accept the actual file contents, instead of the file path, you could simplify the method by getting rid of the stream object:

Public Shared Function ReadSpecifiedLine(contents As String, lineNum As Integer) As String
    Dim linesArray As String() = contents.Split(New Char() {ControlChars.Lf})
    If linesArray.Length > 1 Then
        If Not lineNum > linesArray.Length AndAlso Not lineNum < 0 Then
            Return linesArray(lineNum)
        Else
            Return linesArray(0)
        End If
    Else
        Return contents
    End If
End Function