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A Windows Forms based text editor with HTML output

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2 Jul 2013CPOL
A Windows Forms based text editor with HTML output, implemented with a browser control in edit mode.


NOTICE: As of 10/28/2017, a new version is available. 

Includes the following features:

  • Requires .NET 4.5.1.
  • Fixes save as and load bugs that fired browser dialogs.
  • Insert inline images either by URL or through the file system. File system images are embedded in the resulting HTML.
  • Full programmatic access to HTML, Body HTML, Body Text
  • Set the background color of the body.
  • Insert images.
  • Resize images.
  • Add and edit hyperlinks from text.
  • Add and edit hyperlinks from images.
  • Support for Windows XP SP2 to Windows 8.
  • Support for all versions of IE. 



Sample Image - editor.png



A while ago, I was working on a chat application where one of the chat clients was web based and written with ASP.NET 2.0. The other chat client was a Windows Forms based .NET application written in C#. I needed a rich text editor for my WinForms client that could output HTML, so that the ASP.NET client could display the formatting from the WinForms client. This was ruled out while using the RTF text box.

The solution I worked out was to use a WebBrowser control in edit mode within my WinForms client. Formatting buttons on a toolbar above the web browser are synchronized to the current selection in the WebBrowser control.

This article explains solutions to most of the issues involved in building an editor control from a WebBrowser control. I won't go into everything, as the source code isn't that difficult to browse. But, I do cover some of the tricks necessary to get this to work.

Using the Control

The control is an executable.

You can run it directly with it's main form, or you can embed it as a control in your own app.

To embed it into your own app, simply reference the EXE as if it were a DLL from your app in Visual Studio. 

It should show up in the Toolbox Window in Visual Studio.  

Check the source code for examples of how to access it from your code.

It's a .NET 2.0 control, so it should work in older projects. 

Setting Design Mode 

Applying design mode and establishing an editing template for the document occurs automatically when using the component. But, for reference, here is a brief explanation of how it works.

Applying design mode requires using a COM interface: adding a reference to "Microsoft HTML Object Library", which resolves to MSHTML, and adding a 'using' of 'MSHTML'.

It is necessary to add a body to the control before you can apply changes to the DOM document. To do this, you can simply apply some text to the DocumentText property of the WebBrowser control.

webBrowser1.DocumentText = "<html><body></body></html>"

Next, get a reference to the new DomDocument COM interface, and set the design mode to "On".

IHTMLDocument2 doc =
webBrowser1.Document.DomDocument as IHTMLDocument2;
doc.designMode = "On";

Finally, I replace the context menu for the web browser control so the default IE browser context menu doesn't show up.

webBrowser1.Document.ContextMenuShowing += 
new HtmlElementEventHandler(Document_ContextMenuShowing);

The browser is now in design mode, with a custom method to display the context menu.

Applying Formatting

You can apply formatting and editor functions to a browser control in design mode with the ExecCommand method on browser.Document.

Here are several examples:

public void Cut()
    webBrowser1.Document.ExecCommand("Cut", false, null);
public void Paste()
    webBrowser1.Document.ExecCommand("Paste", false, null);
public void Copy()
    webBrowser1.Document.ExecCommand("Copy", false, null);

Some commands will toggle the formatting state of the current selection.

public void Bold()
    webBrowser1.Document.ExecCommand("Bold", false, null);

public void Italic()
    webBrowser1.Document.ExecCommand("Italic", false, null);

Synchronizing Formatting Buttons with Selected Text

This is a bit more tricky than applying formatting commands to the browser control. I literally query the state of the browser editor selection every 200 ms, and set the toolbar formatting buttons based on this.

private void timer_Tick(object sender, EventArgs e)
    boldButton.Checked = IsBold();
    italicButton.Checked = IsItalic();
    underlineButton.Checked = IsUnderline();
    orderedListButton.Checked = IsOrderedList();
    unorderedListButton.Checked = IsUnorderedList();
    linkButton.Enabled = SelectionType == SelectionType.Text;

    if (Tick != null) Tick();

You'll notice that there is a Tick event that is fired at the end of the timer's tick event. External components can subscribe to this event to update the state of their GUI. For example, they may update the Enabled state of cut/copy/paste/undo/redo buttons based on the state of the Editor control.

I do this by using the COM document interface retrieved from the WebBrowser control with:

IHTMLDocument2 doc = webBrowser1.Document.DomDocument as IHTMLDocument2;

Then I use queryCommandState to determine the state of the current selection:

public bool IsBold()
    return doc.queryCommandState("Bold");

public bool IsItalic()
    return doc.queryCommandState("Italic");

public bool IsUnderline()
    return doc.queryCommandState("Underline");

The link button and font controls are managed in a similar way, but I'll leave that for you to check out in the code.


Focusing the control isn't necessarily simple either. The WebBrowser control itself will not accept focus. Neither will the WebBrowser control's document. But, the body will focus, assuming there is a body element on the control.

private void SuperFocus()
    if (webBrowser1.Document != null && 
        webBrowser1.Document.Body != null)

Of course, you never need to call this method directly. Calling the Focus method on the control will place the focus on the editor control containing the WebBrowser control. The editor control will transfer focus to the WebBrowser's document body automatically, when it receives the GotFocus event.

Retrieving Text or HTML

The BodyHtml and BodyText methods retrieve the body HTML and text, respectively.

Linking to the Component Assembly

In Visual Studio 2005, you can link to an assembly (add a reference), even if the assembly is an executable. The editor is written as a component embedded in a form, so you can add this component to the control palette and drag and drop into your application. The control's name is Editor, under namespace Design.


The .NET 2.0 WebBrowser control can effectively be used as a text editor. This is useful when you need an editor control that can be used as an HTML editor. The implementation is not completely straightforward in some areas. This article attempts to show some of the tricks necessary to get it to work.


  • 10/04/2006 - various bug fixes and design updates / designer support.
  • 10/19/2006 - more bug fixes and more designer support.
  • 10/28/2017 - Upgrade to .net 4.5.1 and VS 2015


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

kevin delafield
United States United States
No Biography provided

Comments and Discussions

NewsBetter way of handling selection change & any other DOM event Pin
John Hind20-Aug-07 2:38
MemberJohn Hind20-Aug-07 2:38 
Generalsystem.invalidoperationexception [modified] Pin
Manoher13-Aug-07 7:55
MemberManoher13-Aug-07 7:55 
GeneralRe: system.invalidoperationexception Pin
Manoher16-Aug-07 7:38
MemberManoher16-Aug-07 7:38 
GeneralRe: system.invalidoperationexception Pin
sanong17-Aug-07 23:50
Membersanong17-Aug-07 23:50 
GeneralExactly what I was looking for, but need it in VB... Pin
Karl Rhodes11-Aug-07 3:16
MemberKarl Rhodes11-Aug-07 3:16 
GeneralRe: Exactly what I was looking for, but need it in VB... Pin
Karl Rhodes13-Aug-07 11:44
MemberKarl Rhodes13-Aug-07 11:44 
GeneralRe: Exactly what I was looking for, but need it in VB... Pin
DumBleBee27-Aug-07 4:36
MemberDumBleBee27-Aug-07 4:36 
GeneralRe: Exactly what I was looking for, but need it in VB... Pin
John Couture25-Jan-08 5:41
MemberJohn Couture25-Jan-08 5:41 
QuestionRe: Exactly what I was looking for, but need it in VB... Pin
Tim Stokes4-Oct-07 1:41
MemberTim Stokes4-Oct-07 1:41 
QuestionError when closing form Pin
thachvv1819-Jul-07 8:45
Memberthachvv1819-Jul-07 8:45 
AnswerRe: Error when closing form Pin
shackrat24-Jul-07 5:07
Membershackrat24-Jul-07 5:07 
AnswerRe: Error when closing form Pin
mbleske3-Apr-08 13:35
Membermbleske3-Apr-08 13:35 
QuestionHow to set the cursor in the WebBrowser to the top Pin
DanCooperstock26-Jun-07 7:55
MemberDanCooperstock26-Jun-07 7:55 
GeneralInsert Bull Pin
Tossi20-Jun-07 23:53
MemberTossi20-Jun-07 23:53 
QuestionIs there any event that content has been changed? Pin
Andrey Nikulin28-May-07 23:35
MemberAndrey Nikulin28-May-07 23:35 
AnswerRe: Is there any event that content has been changed? Pin
Chagel16-Mar-08 7:33
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GeneralRe: Is there any event that content has been changed? Pin
seenit26-Apr-11 14:02
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QuestionShow Problem Pin
xspjob20-May-07 15:52
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GeneralProblem because Printing is asynchronous Pin
DanCooperstock14-May-07 17:24
MemberDanCooperstock14-May-07 17:24 
GeneralRe: Problem because Printing is asynchronous Pin
DanCooperstock26-Jun-07 7:52
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GeneralPerformance Pin
rensdenobel200013-May-07 23:22
Memberrensdenobel200013-May-07 23:22 
GeneralHTML Source index Pin
Manchovski7-May-07 11:12
MemberManchovski7-May-07 11:12 
QuestionHowTo suppress "document changed" MsgBox? Pin
lightwaver30-Apr-07 10:17
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AnswerRe: HowTo suppress "document changed" MsgBox? Pin
lightwaver30-Apr-07 10:43
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AnswerRe: HowTo suppress "document changed" MsgBox? Pin
DerekAndDomino7-Aug-07 8:27
MemberDerekAndDomino7-Aug-07 8:27 

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Posted 12 Sep 2006


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