Visual Basic: Reading and Writing text files

Reading and writing to a text file in visual basic requires the use of the StreamReader and the StreamWriter classes. These are contained in the "System.IO" import file. You can include this file like so:

Imports System.IO

Reading

As it says above, the first line of our code is going to be:

Imports System.IO

As this includes some things we will need. This needs to be put outside any button etc.. events; and right at the top of all the code.

Next we need to create a new StreamReader (in the button code this time):

Dim OurFileReader As StreamReader

Next we will use an open file dialog to see what the user wants to open; and then display whatever the user wants in a textbox for example:

Dim DialogOneResult As DialogResult
DialogOneResult = OpenFileDialog1.ShowDialog

If DialogOneResult = DialogResult.OK Then

OurFileReader = New StreamReader(OpenFileDialog1.FileName)
TextBox1.Text = OurFileReader.ReadToEnd()
OurFileReader.Close()

End If

When we put all the code together it would now display the contents of the text file in the textbox (when the open button was clicked, and a text file was chosen).

Source Code:

Imports System.IO
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim OurFileReader As StreamReader

        Dim DialogOneResult As DialogResult
        DialogOneResult = OpenFileDialog1.ShowDialog

        If DialogOneResult = DialogResult.OK Then

            OurFileReader = New StreamReader(OpenFileDialog1.FileName)
            TextBox1.Text = OurFileReader.ReadToEnd()
            OurFileReader.Close()

        End If
    End Sub
End Class

Writing

Writing files is a lot like reading them, you start with the same import statement. Then we declare a StreamWriter:

Dim OurFileWriter As StreamWriter

Then we almost do the same thing but this time with a savefiledialog:

        Dim SaveDialogResults As DialogResult
        SaveDialogResults = SaveFileDialog1.ShowDialog

        If SaveDialogResults = DialogResult.OK Then

            OurFileWriter = New StreamWriter(SaveFileDialog1.FileName, False)
            OurFileWriter.Write(TextBox1.Text)
            OurFileWriter.Close()

        End If

Putting everything togther you should get something like this:

Imports System.IO
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim OurFileWriter As StreamWriter

        Dim SaveDialogResults As DialogResult
        SaveDialogResults = SaveFileDialog1.ShowDialog

        If SaveDialogResults = DialogResult.OK Then

            OurFileWriter = New StreamWriter(SaveFileDialog1.FileName, False)
            OurFileWriter.Write(TextBox1.Text)
            OurFileWriter.Close()

        End If
    End Sub
End Class

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