Reading .txt file

I am using following code to开发者_如何转开发 read text from a .txt file. But I don't know how to perform search within file and how to read a specific line in the text file, based on search.

Dim vrDisplay = My.Computer.FileSystem.ReadAllText(CurDir() & "\keys.txt")
    MsgBox(vrDisplay)

For an example,

if I want to read the line that contains the word "Start", how to do that

Thanks.

Instead of reading all text, for efficiency's sake,

• Open a FileStream for the file in question.
• Create a StreamReader.
• Loop through, calling ReadLine until either you find the end of the file, or the string contains "Start".

Edit: even if it's required that you keep the entire file in memory, you can still do the above by using a MemoryStream().

It isn't easy to tell from your post if it's the best possible solution, but one solution would be to use regular expressions to find all lines containing the word Start:

^.*\bStart\b.*$

matches an entire line that contains the complete word Start anywhere. It rejects Start as a part of a word, for example Starting won't be matched (that's what the \b word boundary anchors are for).

To use this in VB.NET:

Dim RegexObj As New Regex(
    "^      # Start of line" & chr(10) & _
    ".*     # Any number of characters (anything except newlines)" & chr(10) & _
    "\b     # Word boundary" & chr(10) & _
    "Start  # ""Start""" & chr(10) & _
    "\b     # Word boundary" & chr(10) & _
    ".*     # Any number of characters (anything except newlines)" & chr(10) & _
    "$      # End of line", 
    RegexOptions.Multiline Or RegexOptions.IgnorePatternWhitespace)
AllMatchResults = RegexObj.Matches(vrDisplay)
If AllMatchResults.Count > 0 Then
    ' Access individual matches using AllMatchResults.Item[]
Else
    ' Match attempt failed
End If