vb.net Visual Basic 读取文本文件
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Visual Basic reading text file
提问by nmehta_001
VB is supposed to read each line and show only the corresponding "ItemNo" however what it does is read only the last line of my code and display that, it also does not return my message if i put in an item number that does not yet exist. What would be a way of correcting this so that it chooses only the line with the corresponding "ItemNo" and have it return my message when it fails to find the number.
VB 应该读取每一行并仅显示相应的“ItemNo”，但是它所做的只是读取我代码的最后一行并显示它，如果我输入了尚未输入的项目编号，它也不会返回我的消息存在。有什么方法可以纠正这个问题，以便它只选择具有相应“ItemNo”的行，并在它找不到号码时返回我的消息。
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles CheckNum.Click
Dim File As String = "K:\Access to Computing Folder\Monday\Nicholas Kakou\Assignments\Assignment 2\MicroNut Software Ltd\MicroNut Software Ltd\Data Files\StockFile.dat"
Dim TextLine As String = ""
If System.IO.File.Exists(File) = True Then
Dim objReader As New System.IO.StreamReader(File)
Do While objReader.Peek() <> -1
TextLine = objReader.ReadLine() & vbNewLine
Loop
MsgBox(TextLine)
Else
MsgBox("File Does Not Exist", MsgBoxStyle.OkOnly)
End If
End Sub
回答by Steve
It is not very clear, but supposing that you are searching for a particular string in your text file then you could write this
这不是很清楚，但假设您正在文本文件中搜索特定字符串，那么您可以编写此
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles CheckNum.Click
Dim FileName As String = ".........."
If System.IO.File.Exists(FileName) = True Then
Dim result = File.ReadLines(FileName)
Dim line = result.Where(Function (x) x.Contains("ItemNo")).FirstOrDefault()
If line Is Nothing Then
MsgBox.Show("Not Found")
Else
MsgBox.Show(line)
End If
Else
MsgBox.Show("File Not Found")
End If
End Sub
I have used a fixed string "ItemNo", you should change it to the variable that contains the search text
我使用了固定字符串“ItemNo”，您应该将其更改为包含搜索文本的变量
Notice the usage of File.ReadLines, this methods doesn't read the whole file in memory and allows to start to search the result collection using a lambda expression
注意File.ReadLines的用法，此方法不会读取内存中的整个文件，而是允许使用 lambda 表达式开始搜索结果集合
