我正在创建一个应该将文本写入文本文件的程序,并且应该能够从VB中的文本文件中读取特定行(所以如果我需要读取特定的名称,我可以选择第5行和它将显示在文本框中)。我能够从文本文件中读取文本,但我不知道如何控制特定的行。
这是我的代码:
Public Class Form1
Private Sub btnSubmit_Click(sender As System.Object, e As System.EventArgs) Handles btnSubmit.Click
Dim writer As New System.IO.StreamWriter("/text.txt", True)
writer.WriteLine(txtFirstName.Text)
writer.WriteLine(txtLastName.Text)
writer.WriteLine("-------------------------------------")
writer.Close()
End Sub
Private Sub btnRead_Click(sender As System.Object, e As System.EventArgs) Handles btnRead.Click
Dim reader As New System.IO.StreamReader("/text.txt")
Dim FirstName, LastName As String
FirstName = reader.ReadLine()
LastName = reader.ReadLine()
reader.Close()
txtFirstName.Text = FirstName
txtLastName.Text = LastName
End Sub
Private Sub btnClear_Click(sender As System.Object, e As System.EventArgs) Handles btnClear.Click
txtFirstName.Clear()
txtLastName.Clear()
End Sub
End Class
任何帮助将不胜感激。谢谢!
答案 0 :(得分:10)
您必须阅读所有您感兴趣的行。例如:
Function ReadLineWithNumberFrom(filePath As String, ByVal lineNumber As Integer) As String
Using file As New StreamReader(filePath)
' Skip all preceding lines: '
For i As Integer = 1 To lineNumber - 1
If file.ReadLine() Is Nothing Then
Throw New ArgumentOutOfRangeException("lineNumber")
End If
Next
' Attempt to read the line you're interested in: '
Dim line As String = file.ReadLine()
If line Is Nothing Then
Throw New ArgumentOutOfRangeException("lineNumber")
End If
' Succeded!
Return line
End Using
End Function
这是因为文本行是可变长度记录,并且无法猜测特定行开始处的确切文件偏移量 - 而不是没有索引。
如果您经常需要加载特定的行,您还有其他选择:
将完整的文本文件加载到内存中,例如使用File.ReadAllLines("Foobar.txt")
。这将返回一个String()
数组,您可以通过行号直接访问该数组。
手动创建行号索引。也就是说,逐行处理文本文件,并随时填写Dictionary(Of Integer, Integer)
。键是行号,值是文件偏移量。这使您可以.Seek
直接到特定行的开头,而无需将整个文件保留在内存中。
答案 1 :(得分:4)
试试这个:
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Dim reader As New System.IO.StreamReader("C:\text.txt")
Dim allLines As List(Of String) = New List(Of String)
Do While Not reader.EndOfStream
allLines.Add(reader.ReadLine())
Loop
reader.Close()
txtFirstName.Text = ReadLine(5, allLines)
txtLastName.Text = ReadLine(6, allLines)
End Sub
Public Function ReadLine(lineNumber As Integer, lines As List(Of String)) As String
Return lines(lineNumber - 1)
End Function
如果你有一个文件:
Line 1
Line 2
Line 3
Line 4
My Name
My LastName
您的姓名文本框将包含“我的姓名”,而您的姓氏文本框将包含“我的姓氏”。
答案 2 :(得分:2)
这很简单,试试这个:
Dim strLineText As String
Dim intLineNumber As Integer
LineNumber=3
myLine = File.ReadAllLines("D:\text.txt").ElementAt(LineNumber).ToString
答案 3 :(得分:0)
又一个选择
Private Function readNthLine(fileAndPath As String, lineNumber As Integer) As String
Dim nthLine As String = Nothing
Dim n As Integer
Try
Using sr As StreamReader = New StreamReader(fileAndPath)
n = 0
Do While (sr.Peek() >= 0) And (n < lineNumber)
sr.ReadLine()
n += 1
Loop
If sr.Peek() >= 0 Then
nthLine = sr.ReadLine()
End If
End Using
Catch ex As Exception
Throw
End Try
Return nthLine
End Function
答案 4 :(得分:0)
我尝试了这一点,效果很好。使用VB Express test.txt中的内容:
line1
line2
1
John
然后以我添加的形式
textbox1
textbox2
label1
label2
和一个button
。
按钮内的代码:
Private Sub Button2_Click_1(sender As Object, e As EventArgs) Handles Button2.Click
Dim myLine As String
Dim lineNumber0 As Integer
lineNumber0 = 0
Dim lineNumber1 As Integer
lineNumber1 = 1
Dim lineNumber2 As Integer
lineNumber2 = 2
Dim lineNumber3 As Integer
lineNumber3 = 3
TextBox1.Text=File.ReadAllLines("D:\test.txt").ElementAt(lineNumber0).ToString
TextBox2.Text=File.ReadAllLines("D:\test.txt").ElementAt(lineNumber1).ToString
Label1.Text = File.ReadAllLines("D:\test.txt").ElementAt(lineNumber2).ToString
Label2.Text = File.ReadAllLines("D:\test.txt").ElementAt(lineNumber3).ToString
End Sub