Basics
More Complex Examples
Basic controls with Visual Basic 2008
Open and Save File Dialogs
OpenFileDialogs:
OpenFileDialogs are used to browse your computer, select a file and
open it. You can also set the Filter attribute to allow only certain
file extensions. FileDialogs are usually called with the ShowDialog
command.
SaveFileDialogs:
SaveFileDialogs are also used to browse your computer, select a file
and save it. If you ever used the Save As function of some application,
you would know exactly what these dialogs look like.
We will build a simple example to give you an idea of how these dialogs
work.
Create a new project. From the Toolbox menu create the following
controls on the form:
OpenFileDialog1
SaveFileDialog1
Label1
Label2
TextBox1
TextBox2
TextBox3
TextBox4
TextBox5
TextBox6
TextBox8
Button1
Button2
Arrange the controls as in figure 9:
Figure 9: Open & Save Dialogs
Change the text of Button1 to "Open" and Button2 to "Save". Change the text of Label1 to "Name" and Label2 to "Age". Create a String array called "Names" to hold 4 data entries and an Integer array called "Age" to hold 4 data entries using the "Dim" command. Use Button1 with the FileOpenDialog, ShowDialog and Button2 with the FileSaveDialog, ShowDialog command.
Public Class Form1
Dim Names(3) As String, Age(3)
As Integer
Private Sub Button1_Click(ByVal sender
As System.Object, ByVal
e As
System.EventArgs) Handles Button1.Click
OpenFileDialog1.Filter = "Data files (*.dat)|*.dat"
OpenFileDialog1.ShowDialog()
FileOpen(1, OpenFileDialog1.FileName, OpenMode.Random)
FileGet(1, Names) : FileGet(1, Age)
TextBox1.Text = Names(0)
TextBox2.Text = Names(1)
TextBox3.Text = Names(2)
TextBox4.Text = Names(3)
TextBox5.Text = Age(0)
TextBox6.Text = Age(1)
TextBox7.Text = Age(2)
TextBox8.Text = Age(3)
FileClose(1)
End Sub
Private Sub Button2_Click(ByVal sender
As System.Object, ByVal e
As
System.EventArgs) Handles Button2.Click
SaveFileDialog1.Filter = "Data files (*.dat)|*.dat"
SaveFileDialog1.ShowDialog()
FileOpen(1, SaveFileDialog1.FileName, OpenMode.Random)
Names(0) = TextBox1.Text
Names(1) = TextBox2.Text
Names(2) = TextBox3.Text
Names(3) = TextBox4.Text
Age(0) = TextBox5.Text
Age(1) = TextBox6.Text
Age(2) = TextBox7.Text
Age(3) = TextBox8.Text
FilePut(1, Names) : FilePut(1, Age)
FileClose(1)
End Sub
End Class
We
added the Filter "Data files (*.dat)|*.dat" to both FileDialogs so that
when we try to open a file only files with the .dat extension can be
showed. When we save our data to a file the .dat extension will
automatically be added to our filename. Neat don't you think. Our
FileDialogs does not actually open or save our file, but in fact only
gives us a browsing tool to select a path and filename. We use the
FileOpen command to open a file. Files can be opened in different modes
to which I will give you more information later on, but for now lets
stick to OpenMode.Random. You will notice that after both FileOpen and
FileClose methods we use the number (1). It is to specify the file
number. To either write to or read from a file we use the commands
FilePut or FileGet with the file number.
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