Step 7: Add Dialog Components to Your Form
To enable your program to open picture files and choose a background color, in this step, you add an OpenFileDialog component and a ColorDialog component to your form.
A component is like a control in some ways. You use the Toolbox to add a component to your form, and you set its properties using the Properties window. But unlike a control, adding a component to your form doesn't add a visible item that the user can see on the form. Instead, it provides certain behaviors that you can trigger with code. It's a component that opens an Open File dialog box.
For a video version of this topic, see Tutorial 1: Create a Picture Viewer in Visual Basic - Video 3 or Tutorial 1: Create a Picture Viewer in C# - Video 3. These videos use an earlier version of Visual Studio, so there are slight differences in some menu commands and other user interface elements. However, the concepts and procedures work similarly in the current version of Visual Studio.
To add dialog components to your form
Choose the Windows Forms Designer (Form1.cs [Design] or Form1.vb [Design]) and then open the Dialogs group in the Toolbox.
The Dialogs group in the Toolbox has components that open many useful dialog boxes for you, which can be used for opening and saving files, browsing folders, and choosing fonts and colors. You use two dialog components in this project: OpenFileDialog and ColorDialog.
To add a component called openFileDialog1 to your form, double-click OpenFileDialog. To add a component called colorDialog1 to your form, double-click ColorDialog in the Toolbox. (You use that one in the next tutorial step.) You should see an area at the bottom of Windows Forms Designer (beneath the Picture Viewer form) that has an icon for each of the two dialog components that you added, as shown in the following picture.
Choose the openFileDialog1 icon in the area at the bottom of the Windows Forms Designer. Set two properties:
Set the Filter property to the following (you can copy and paste it):
JPEG Files (*.jpg)|*.jpg|PNG Files (*.png)|*.png|BMP Files (*.bmp)|*.bmp|All files (*.*)|*.*
Set the Title property to the following: Select a picture file
The Filter property settings specify the kinds of file types that will display in the Select a picture file dialog box.
To see an example of the Open File dialog box in a different application, open Notepad or Paint, and on the menu bar, choose File, Open. Notice how there's a Files of type drop-down list at the bottom. You just used the Filter property in the OpenFileDialog component to set that up. Also, notice how the Title and Filter properties are bold in the Properties window. The IDE does that to show you any properties that have been changed from their default values.
To continue or review
To go to the next tutorial step, see Step 8: Write Code for the Show a Picture Button Event Handler.
To return to the previous tutorial step, see Step 6: Name Your Button Controls.