help me_about a problem of reading data from a file

help me_about a problem of reading data from a file

• Sayed Zeeshan

  i have resolved this problem.code as follows:

  Imports system.io
  Public Class 禁 系

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
  '打 通信端口
  Try
  DoorPort.Open()
  ADPort.Open()
  Catch ex As Exception
  MessageBox.Show(ex.Message)
  End Try

  '新建日志文件
  Dim filetitle As String = filedate.Year + "_" + filedate.Month + "_" + filedate.Day '日志文件名
  Dim path As String = "logs\" + filetitle + ".txt"
  If File.exists(path) = False Then
  swlog = File.CreateText(path)
  Else
  swlog = File.AppendText(path)
  End If

  AddHandler DoorPort.DataReceived, AddressOf swapevent
  End Sub

  Dim contrastTable(0 To 1000, 0 To 1) As String ' 照表 ，第一 是 ，第二 是 像
  Dim filedate As Date = New Date()
  Dim logtime As String = filedate.Now()
  Dim logdoor As String
  Dim logcamera As String
  Dim logmonitor As String
  Dim doorno As String '定
  Dim camerano As String '定 像
  Dim count As Integer = 0 '定 照表的行
  Dim swlog As StreamWriter
  Dim monitor As Integer '定 器
  Dim outputstring1 As String
  Dim outputstring2 As String

  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  ' 取 照表到一 中
  Try
  Using sr As StreamReader = New StreamReader("contrast.txt")
  Dim line As String
  While sr.Peek <> -1
  line = sr.ReadLine()
  doorno = line.Substring(0, 4).Trim()
  camerano = line.Substring(5).Trim()
  contrastTable(count, 0) = doorno
  contrastTable(count, 1) = camerano
  count += 1
  End While
  monitor = CType(contrastTable(0, 1), Integer)
  sr.Close()
  End Using
  Catch ex As Exception
  ' Let the user know what went wrong.
  MessageBox.Show(ex.Message)
  End Try

  End Sub

  Private Function findCameraNo(ByVal doorno2 As String) As String
  Dim i As Integer
  Dim camerano2 As String
  For i = 0 To count
  If contrastTable(i, 0) = doorno2 Then
  camerano2 = contrastTable(i, 1)
  End If
  Next
  Return camerano2
  End Function

  Private Sub swapevent(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs)
  ' 取 禁系 的
  Dim line As String
  Dim monitor2 As Integer
  line = DoorPort.ReadLine()
  doorno = line.Substring(0, 3)
  ' 的 像
  camerano = findCameraNo(doorno)
  ' 循 示
  If monitor2 = -1 Then
  monitor2 = monitor
  End If
  outputstring1 = monitor2 + " M" + " a"
  outputstring2 = camerano + " #" + " a"
  ADPort.Write(outputstring1) ' AD矩 送 器的命令
  ADPort.Write(outputstring2) ' AD矩 送 像 的命令
  monitor2 -= 1

  logdoor = doorno
  logcamera = camerano
  logmonitor = monitor2
  ' 入日志文件
  swlog.WriteLine(logtime + vbTab + logdoor + vbTab + logcamera + vbTab + logmonitor)
  ' 入界面的richtextbox
  RichTextBox1.AppendText(logtime + vbTab + logdoor + vbTab + logcamera + vbTab + logmonitor + vbCrLf)
  End Sub

  Private Sub form1_formclosing(ByVal sender As System.Object, ByVal e As System.EventArgs)
  ADPort.Close()
  DoorPort.Close()
  End Sub
  End Class

  well, although this is done before i took a look at your advices , thanks NateV for your advice all the same.

  
  

• Natural_orange

  en , the problem still occurces

  well ,thanks all the same!

  
  

• TMB

  may be i should write all the code here :

  Public Class

      Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
          '
          Try
              DoorPort.Open()
              ADPort.Open()
          Catch ex As Exception
              MessageBox.Show(ex.Message)
          End Try

          '
          Dim filetitle As String = filedate.Year + "_" + filedate.Month + "_" + filedate.Day '
          Dim path As String = "logs\" + filetitle + ".txt"
          If File.exists(path) = False Then
              swlog = File.CreateText(path)
          Else
              swlog = File.AppendText(path)
          End If

          AddHandler DoorPort.DataReceived, AddressOf swapevent
      End Sub

      Dim contrastTable(,) As String ' , ,
      Dim filedate As Date = New Date()
      Dim logtime As String = filedate.Now()
      Dim logdoor As String
      Dim logcamera As String
      Dim logmonitor As String
      Dim doorno As String '
      Dim camerano As String '
      Dim count As Integer = 0 '
      Dim swlog As StreamWriter
      Dim monitor As Integer '
      Dim outputstring1 As String
      Dim outputstring2 As String

      Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
          '
          Try
              Using sr As StreamReader = My.Computer.FileSystem.OpenTextFileReader("contrast.txt")
                  Dim line As String
                  While sr.Peek <> -1
                      line = sr.ReadLine()
                      doorno = line.Substring(0, 4).Trim()
                      camerano = line.Substring(5).Trim()
                      count += 1
                      contrastTable(count, 0) = doorno
                      contrastTable(count, 1) = camerano
                  End While
                  monitor = CType(contrastTable(0, 1), Integer)
                  sr.Close()
              End Using
          Catch ex As Exception
              ' Let the user know what went wrong.
              MessageBox.Show("The file could not be read:" + ex.Message)
          End Try

      End Sub

      Private Function findCameraNo(ByVal doorno2 As String) As String
          Dim i As Integer
          Dim camerano2 As String
          For i = 0 To count
              If contrastTable(i, 0) = doorno2 Then
                  camerano2 = contrastTable(i, 1)
              End If
          Next
          Return camerano2
      End Function

      Private Sub swapevent(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs)
          '
          Dim line As String
          Dim monitor2 As Integer
          line = DoorPort.ReadLine()
          doorno = line.Substring(0, 3)
          '
          camerano = findCameraNo(doorno)
          '
          If monitor2 = -1 Then
              monitor2 = monitor
          End If
          outputstring1 = monitor2 + " M" + " a"
          outputstring2 = camerano + " #" + " a"
          ADPort.Write(outputstring1) ' AD
          ADPort.Write(outputstring2) ' AD
          monitor2 -= 1

          logdoor = doorno
          logcamera = camerano
          logmonitor = monitor2
          '
          swlog.WriteLine(logtime + vbTab + logdoor + vbTab + logcamera + vbTab + logmonitor)
          ' richtextbox
          RichTextBox1.AppendText(logtime + vbTab + logdoor + vbTab + logcamera + vbTab + logmonitor + vbCrLf)
      End Sub

      Private Sub form1_formclosing(ByVal sender As System.Object, ByVal e As System.EventArgs)
          ADPort.Close()
          DoorPort.Close()
      End Sub
  End Class

  
  

• Rakesh Kashnia

  Hi,

  This is because you check whether "line" is nothing in the end, which means it will fail on Substring() if line is nothing.

  Here's an alternative way of iterating through all lines of text in a file:

  While sr.Peek <> -1

  line = sr.ReadLine()

  ...

  End While

  Or you can add the check in the beggining(ie by assigning "line" an initial variable and use Do While)

  
  
  

• ryandailey21

  Hi there,
  
  The problem you are seeing now (after switching to the method Ryan Tsai suggested) is not your file reading routine but the fact that your two dimensional array of strings (contrastTable) has not been initialised. The implication of this is that you get the exception you're seeing.
  
  You need to actually define the size of the contrastTable array before you use it. It may be difficult to actually determine what size it will be (since this relies on how many lines are in your file) but you need to set it to something.
  
  I have attached a modification to your code a bit later in this post, where I have set contrastTable so that is has 1000 "rows" and 2 "columns" but you should, of course, change this as necessary. You could also consider using some sort of other Collection construct but if you're happy with your current setup then it's not necessary (could be slightly better though).
  
  Also, with the postion of the count += 1 in your file reading code, the implication of putting this statement where you have is that the first "row" of contrastTable (Row Index 0) is never populated and so when you assign the monitor variable like you have in your code:
  
  monitor = CType(contrastTable(0, 1), Integer)
  
  It won't contain anything meaningful. In the below example, I have also changed the positioning of your count += 1 statement so that the first "row" (Row Index 0) of contrastTable is populated.
  
  Also, with the way you have defined your StreamReader, you need to be mindful of where you place the text file so that it can be found and read by your program. Just a little word of advice/warning as you might encounter an error if the text file isn't in the place the StreamReader was expecting it to be.
  
  And one final thing, you don't need the call to sr.Close() as the Using statement will do the clean up for you (and call the Close() function by itself). Doesn't really hurt anyone to keep it in there, though, so I have not touched that function call.
  
  Anyway, below is the modification I've made to your code, have a go & see if it works:
  
  

  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
      ReDim contrastTable(1000, 2) 'Make sure the array is usable

      Try
          Using sr As StreamReader = My.Computer.FileSystem.OpenTextFileReader("contrast.txt")
              Dim line As String

              While sr.Peek <> -1
                  line = sr.ReadLine()
                  doorno = line.Substring(0, 4).Trim()
                  camerano = line.Substring(5).Trim()
                  contrastTable(count, 0) = doorno
                  contrastTable(count, 1) = camerano

                  count += 1 'Moved here so that the first row is populated
              End While
              monitor = CType(contrastTable(0, 1), Integer)
              sr.Close()
          End Using
    Catch ex As Exception
      ' Let the user know what went wrong.
      MessageBox.Show("The file could not be read:" + ex.Message)
    End Try
  End Sub

  Hope that helps a bit, but sorry if it doesn't
  
  
  
  
  
  
  
• help me_about a problem of reading data from a file