`MessageBox`

In C# programs based on Windows Forms, MessageBox is a dialog. Dialog boxes interrupt users—they force users to respond before further action is taken.

Method notes

MessageBox.Show is useful if a warning or error is important. We must choose the number of arguments to pass to MessageBox.Show—we can use just 1, but often more are needed.

Some examples

Here are examples of MessageBox.Show with 1 to 7 arguments. You can match up the images to the code. For more complex dialogs, we need more arguments.

Tip We control the message body text, the buttons, the icons, the message box title, and the default button focus.

Info MessageBox.Show calls into different implementations of the function based on the parameter lists.

using System.Windows.Forms;

namespace WindowsFormsApp5
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            // Use 1 argument.
            MessageBox.Show("Dot Net Perls is awesome.");

            // Use 2 arguments.
            MessageBox.Show("Dot Net Perls is awesome.",
                "Important Message");

            // Use 3 arguments.
            DialogResult result1 = MessageBox.Show("Is Dot Net Perls awesome?",
                "Important Question",
                MessageBoxButtons.YesNo);

            // Use 4 arguments.
            DialogResult result2 = MessageBox.Show("Is Dot Net Perls awesome?",
                "Important Query",
                MessageBoxButtons.YesNoCancel,
                MessageBoxIcon.Question);

            // Use 5 arguments.
            DialogResult result3 = MessageBox.Show("Is this website awesome?",
                "The Question",
                MessageBoxButtons.YesNoCancel,
                MessageBoxIcon.Question,
                MessageBoxDefaultButton.Button2);

            // Test DialogResult.
            if (result1 == DialogResult.Yes &&
                result2 == DialogResult.Yes &&
                result3 == DialogResult.No)
            {
                MessageBox.Show("You answered yes, yes and no.");
            }

            // Use 7 arguments.
            MessageBox.Show("Dot Net Perls is the best.",
                "Critical Warning",
                MessageBoxButtons.OKCancel,
                MessageBoxIcon.Warning,
                MessageBoxDefaultButton.Button1,
                MessageBoxOptions.RightAlign,
                true);
        }
    }
}

Notes, `static`

The MessageBox.Show method is a static method. This means you do not need to create a new MessageBox() anywhere in your code.

Detail You can type "MessageBox" and press the period, and then select the "Show" entry.

Here The MessageBox.Show method is used in the Form1 constructor, but in your code, you should call it when a dialog is needed.

Also For a parameter such as "MessageBoxButtons", type in "MessageBoxButtons" and press period to see all the options.

using System.Windows.Forms;

namespace WindowsFormsApp5
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            // Type this part.
            MessageBox.Show( //...
        }
    }
}

Parameter order

The order of the parameters in the MessageBox.Show method calls is important. The compiler applies overload resolution to call the best method in the method group.

`DialogResult`

This is an enum. This means you cannot create a new DialogResult with the "new" operator. First assign your variable to the result of MessageBox.Show.

Next Type in "==" and Visual Studio will suggest options from the DialogResult enumeration.

Tip You can compare DialogResult like you would compare an integral type such as int. You can even use it in a switch.

Overloads

There are several more overloads of MessageBox.Show that are not shown in this document. They allow you to specify owner windows, which you do not need to do in simple cases.

Detail The IWin32Window owner parameter is an interface type. Interfaces treat object instances in a more general way.

`HelpNavigator` parameter

The MessageBox.Show method also has overloads that allow you to specify Help options. In my experience, these options are not usually needed.

A summary

MessageBox.Show is an effective approach to dialog boxes in Windows Forms. We looked at screenshots of the results of the MessageBox.Show method.

MessageBox