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| Title | Read a file containing a list of numbers into an array in two ways in VB .NET. |
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| Description | This example shows how to read a file containing a list of numbers into an array in two ways in VB .NET. It reads the file one line at a time using a StreamReader object's ReadLineMethod. It then reads the file in one string using the ReadToEnd method, separates the items with the Split method, and loops through the result converting the items into Integers. |
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| Keywords | array, file, I/O, IO, StreamWriter, StringBuilder |
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| Categories | Files and Directories |
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Note: Use the net_make_numbers program included to generate the test data file. Be sure to use the same number of items in both programs.
When the user clicks the LineInput button, the program reads the file one line at a time using a StreamReader object's ReadLine method.
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Private Sub btnLineInput_Click(ByVal sender As _
System.Object, ByVal e As System.EventArgs) Handles _
btnLineInput.Click
Dim start_time As Date = Now
' Get the number of numbers.
Dim num As Integer = Integer.Parse(txtNumNumbers.Text)
' Size the array.
Dim the_array(num - 1) As Integer
' Read the numbers.
Dim stream_reader As New StreamReader(txtFile.Text)
For i As Integer = 0 To num - 1
the_array(i) = _
Integer.Parse(stream_reader.ReadLine())
Next i
stream_reader.Close()
Dim stop_time As Date = Now
Dim elapsed_time As TimeSpan = _
stop_time.Subtract(start_time)
lblLineInput.Text = _
elapsed_time.TotalSeconds.ToString("0.0000")
End Sub
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When the user clicks the Split button, the program reads the entire file into a string by calling the StreamReader's ReadToEnd method. It uses the String's Replace and Split methods to separate the lines and then parses each number.
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Private Sub btnSplit_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnSplit.Click
Dim start_time As Date = Now
' Get the number of numbers.
Dim num As Integer = Integer.Parse(txtNumNumbers.Text)
' Size the array.
Dim the_array(num - 1) As Integer
' Read the numbers.
Dim stream_reader As New StreamReader(txtFile.Text)
Dim all_text As String = stream_reader.ReadToEnd()
stream_reader.Close()
' Separate the numbers.
all_text.Replace(vbLf, vbCr)
Dim lines() As String = all_text.Split(CChar(vbCr))
' Parse the numbers.
For i As Integer = 0 To num - 1
the_array(i) = Integer.Parse(lines(i))
Next i
Dim stop_time As Date = Now
Dim elapsed_time As TimeSpan = _
stop_time.Subtract(start_time)
lblSplit.Text = _
elapsed_time.TotalSeconds.ToString("0.0000")
End Sub
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In my tests, the first version was about twice as fast as the second vesion.
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