C# MessageBox.Show

Dialog boxes interrupt users. They force users to respond before further action is taken. This is necessary in some situations. MessageBox.Show is useful if a warning is important or a serious error occurred.

Example

To start, the MessageBox.Show method is a static method, which means you do not need to create a new MessageBox() anywhere in your code. Instead, you can simply type "MessageBox" and press the period, and then select Show.
Static MethodIn this example, the MessageBox.Show method is used in the Form1_Load event handler. To make the Form1_Load event handler, create a new Windows Forms application and double-click on the window in the designer.

Windows Forms program that uses MessageBox: C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
 public Form1()
 {
     InitializeComponent();
 }

 private void Form1_Load(object sender, EventArgs e)
 {
     //
     // The simplest overload of MessageBox.Show. [1]
     //
     MessageBox.Show("Dot Net Perls is awesome.");
     //
     // Dialog box with text and a title. [2]
     //
     MessageBox.Show("Dot Net Perls is awesome.",
  "Important Message");
     //
     // Dialog box with two buttons: yes and no. [3]
     //
     DialogResult result1 = MessageBox.Show("Is Dot Net Perls awesome?",
  "Important Question",
  MessageBoxButtons.YesNo);
     //
     // Dialog box with question icon. [4]
     //
     DialogResult result2 = MessageBox.Show("Is Dot Net Perls awesome?",
  "Important Query",
  MessageBoxButtons.YesNoCancel,
  MessageBoxIcon.Question);
     //
     // Dialog box with question icon and default button. [5]
     //
     DialogResult result3 = MessageBox.Show("Is Visual Basic awesome?",
  "The Question",
  MessageBoxButtons.YesNoCancel,
  MessageBoxIcon.Question,
  MessageBoxDefaultButton.Button2);
     //
     // Test the results of the previous three dialogs. [6]
     //
     if (result1 == DialogResult.Yes &&
  result2 == DialogResult.Yes &&
  result3 == DialogResult.No)
     {
  MessageBox.Show("You answered yes, yes and no.");
     }
     //
     // Dialog box that is right-aligned (not useful). [7]
     //
     MessageBox.Show("Dot Net Perls is the best.",
  "Critical Warning",
  MessageBoxButtons.OKCancel,
  MessageBoxIcon.Warning,
  MessageBoxDefaultButton.Button1,
  MessageBoxOptions.RightAlign,
  true);
     //
     // Dialog box with exclamation icon. [8]
     //
     MessageBox.Show("Dot Net Perls is super.",
  "Important Note",
  MessageBoxButtons.OK,
  MessageBoxIcon.Exclamation,
  MessageBoxDefaultButton.Button1);
 }
    }
}

In Form1_Load, there are eight calls to the MessageBox.Show method using different overloads. The Form1_Load method is executed immediately after the program starts. When run, the program shows all the dialogs in sequential order.
OverloadTyping in the options. The easiest way to use MessageBox.Show is to type in "MessageBox", and then press period, and then select Show. Next, Visual Studio shows a popup with the overload list. You can scroll through the overload lists.
EnumThe order of the parameters in the MessageBox.Show method calls is important. The parameter order gives the compiler the ability to apply overload resolution to call the best method in the method group.

DialogResult

In Windows Forms, DialogResult is not an actual class but is a named constant from an enumeration. 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. You can compare DialogResult like you would compare an integral type such as int. You can even use it in a switch.
DialogResult

More 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. The IWin32Window owner parameter is an interface type.
InterfaceHelpNavigator parameter. The MessageBox.Show method also has overloads that allow you to specify Help options. In my experience, these options are not used most of the time, so I leave the specifics here up to MSDN.

Obtrusive

When designing programs for the end user, it is usually best to make non-critical errors as unobtrusive as possible. The Microsoft User Experience Guidelines provide many tips on dialog boxes.
Error Messages: MSDN

Summary

We saw examples of calling MessageBox.Show in C# programs using Windows Forms. We looked at the actual screenshots of the results of MessageBox.Show method calls, and also tested the DialogResult enumeration.