The Help Class encapsulates the HTML Help 1.0 engine. You can use the Help object to show compiled Help files (.chm) or HTML files in the HTML Help format. Compiled Help files provide table of contents, index, search, and keyword links in pages. Shortcuts work only in compiled Help files. You can generate HTML Help 1.x files with a free tool from Microsft called HTML Help Workshop.

An easy way to show a compiled help file in a second window:

C#

Help.ShowHelp(this, helpProviderMain.HelpNamespace);

VB.NET

Help.ShowHelp(Me, hlpProviderMain.HelpNamespace)

You can provide help for message box in different ways. You can configure a MessageBox to show a Help button or not. Also you can configure MessageBox in a way that when the user requests for help by click on Help button or by pressing F1, it show a CHM file or navigate to a URL or perform a custom action. Here are some examples in this topic.

In all below examples, the MessageBox would be like this:

Show a CHM file and navigate to a keyword (index)

MessageBox.Show("Some Message", "Title", MessageBoxButtons.YesNoCancel,
    MessageBoxIcon.Question, MessageBoxDefaultButton.Button3, 0,
    "help.chm", HelpNavigator.KeywordIndex, "SomeKeyword");

Show a CHM file and navigate to a topic

MessageBox.Show("Some Message", "Title", MessageBoxButtons.YesNoCancel,
    MessageBoxIcon.Question, MessageBoxDefaultButton.Button3, 0,
    "help.chm", HelpNavigator.Topic, "/SomePath/SomePage.html");

Show a CHM file and navigate first help page in table of contents

MessageBox.Show("Some Message", "Title", MessageBoxButtons.YesNoCancel,
    MessageBoxIcon.Question, MessageBoxDefaultButton.Button3, 0,
    "help.chm");

Open default browser and navigate to a URL

MessageBox.Show("Some Message", "Title", MessageBoxButtons.YesNoCancel,
    MessageBoxIcon.Question, MessageBoxDefaultButton.Button3, 0,
    "http://example.com");

Perform custom action on when pressing Help Button or F1 Key

In this case you should handle HelpRequested event of parent of MessageBox and perform custom operation:

private void Form1_HelpRequested(object sender, HelpEventArgs hlpevent)
{
    // Perform custom action, for example show a custom help form
    var f = new Form();  
    f.ShowDialog();
}

Then you can show the MessageBox with Help button:

MessageBox.Show("Some Message", "Title", MessageBoxButtons.YesNoCancel,
    MessageBoxIcon.Question, MessageBoxDefaultButton.Button3, 0, true);

Or show it without Help button:

MessageBox.Show("Some Message", "Title", MessageBoxButtons.YesNoCancel,
    MessageBoxIcon.Question, MessageBoxDefaultButton.Button3, 0, false);

You can provide help for OpenFileDialog, SaveFileDialog and ColorDialog. To do so set ShowHelp property of dialog to true and handle HelpRequest event for dialog:

void openFileDialog1_HelpRequest(object sender, EventArgs e)
{
    //Perform custom action
    Help.ShowHelp(this, "Http://example.com");
}

Note

• The event will be raised only if you set ShowHelp to true.
• The event will be raised only by click on Help button and will not raise using F1 key.

In the image below you can see an OpenFileDialog with a Help button:

When a user press F1 on a control or click on Help button of form (?) and then clicks on a control the HelpRequested event will be raised.

You can handle this event to provide custom action when user requests help for controls or form.

The HelpRequested supports bubble up mechanism. It fires for your active control and if you don't handle the event and not set Handled property of its event arg to true, then it bubbles up to the parent control hierarchy up to form.

For example if you handle HelpRequested event of the form like below, then when you press F1 a message box will pop up and show name of active control, but for textBox1 it will show a different message:

private void Form1_HelpRequested(object sender, HelpEventArgs hlpevent)
{
    var c = this.ActiveControl;
    if(c!=null)
        MessageBox.Show(c.Name);
}
private void textBox1_HelpRequested(object sender, HelpEventArgs hlpevent)
{
    hlpevent.Handled = true;
    MessageBox.Show("Help request handled and will not bubble up");
}

You can perform any other custom action like using navigating to a URL or showing a CHM file using Help class.

You can use Help class in code, to provide these kinds of help:

• Show a help pop-up for a control
• Open a CHM file based on context (Show table of content, Show a keyword or index, show a topic)
• Navigate to a URL using default browser

Show Help pop-up window

You can use Help.ShowPopup to display a help pop-up window:

private void control_MouseClick(object sender, MouseEventArgs e)
{
    var c = (Control)sender;
    var help = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, " +
               "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
    if (c != null)
        Help.ShowPopup(c, "Lorem ipsum dolor sit amet.", c.PointToScreen(e.Location));
}

It will show such help pop-up at your mouse pointer location:

Show CHM Help file

You can use different overloads of Help.ShowHelp method, to show a CHM file and navigate to a keyword, a topic, index or table of content:

Show Help Table of Content

Help.ShowHelp(this, "Help.chm"); 

Show Help for specific Keyword (index)

Help.ShowHelp(this, "Help.chm", HelpNavigator.Index, "SomeKeyword");

Show Help for specific Topic

Help.ShowHelp(this, "Help.chm", HelpNavigator.Topic, "/SomePath/SomePage.html");

Show Url

You can show any URL in default browser using ShowHelp method:

Help.ShowHelp(this, "Http://example.com");

You can show a Help Button at title-bar of a Form. To do so, you should:

1. Set HelpButton property of form to true.
2. Set MinimizeBox and MaximizeBox to false.

Then a help button will appear on title-bar of Form:

Also when you click on Help button, the cursor will be changed to a ? cursor:

Then if you click on a Control or Form, the HelpRequested event will be raised and also if you have setup a HelpProvider, the help for the control will be shown using HelpProvider.

If you have a Form with MinimizeBox and MaximizeBox set to true, then you can not show Help button on title-bar of Form and will lose the feature of click on help button to convert it to help cursor to be able to click on controls to show help.

You can make a menu item on MenuStrip act like standard Help Button. To do so, add a MenuStrip to the form and add a ToolStripMenuItem to it, then handle Click event of the item:

private const int WM_SYSCOMMAND = 0x0112;
private const int SC_CONTEXTHELP = 0xF180;
[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
private void helpToolStripMenuItem_Click(object sender, EventArgs e)
{
    SendMessage(this.Handle, WM_SYSCOMMAND, SC_CONTEXTHELP, 0);
}

Note: If you want to do it using a Button, you also need to set button1.Capture = false; before sending the message. But it's not necessary for a ToolStripMenuItem.

Then when you click on the help menu, the cursor will be changed to ? cursor and will act like when you click on standard Help button:

You can detect when a user Clicked on a HelpButton on title-bar of form by handling HelpButtonClicked. You can let the event continue or cancel it by setting Cancel property of its event args to true.

private void Form1_HelpButtonClicked(object sender, CancelEventArgs e)
{
    e.Cancel = true;
    //Perform some custom action
    MessageBox.Show("Some Custom Help");
}