`OpenFileDialog`

Users often need to select files in a program. In Windows Forms, we use the OpenFileDialog control. We access properties of this control with VB.NET.

This dialog makes development faster and easier. In most situations, it makes no sense to use a different way to select files from a UI.

To start, please create a new Windows Forms project in Visual Studio. Add a Button and an OpenFileDialog. Double-click on the Button to create a click event handler.

Then In the Button1_Click event handler, add a called to OpenFileDialog1.ShowDialog.

Tip Assign a DialogResult Dim to the result of the ShowDialog Function. Then test the DialogResult with an If-Statement.

Result When you execute this program, click the button. An OpenFileDialog, similar to the screenshot, will appear.

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        ' Call ShowDialog.
        Dim result As DialogResult = OpenFileDialog1.ShowDialog()

        ' Test result.
        If result = Windows.Forms.DialogResult.OK Then
            ' Do something.
        End If

    End Sub

End Class

Read file

Next, we read a file the user selects in the OpenFileDialog. We detect the DialogResult.OK value—this occurs when the OK button is pressed.

Note We then use File.ReadAllText to load in the text file. This performs the actual file loading.

Finally When the OK button is pressed, the length of the file is displayed in the title bar of the window.

Imports System.IO

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        ' Call ShowDialog.
        Dim result As DialogResult = OpenFileDialog1.ShowDialog()

        ' Test result.
        If result = Windows.Forms.DialogResult.OK Then

            ' Get the file name.
            Dim path As String = OpenFileDialog1.FileName
            Try
                ' Read in text.
                Dim text As String = File.ReadAllText(path)

                ' For debugging.
                Me.Text = text.Length.ToString

            Catch ex As Exception

                ' Report an error.
                Me.Text = "Error"

            End Try
        End If

    End Sub

End Class

Properties

We use properties to perform many of the important tasks with OpenFileDialog. We use the FileName property to get the path selected by the user.

A custom file dialog is rarely needed—the OpenFileDialog handles most common requirements. It has many features and properties.