BUG: Application Error When You Use DoEvents in WebBrowser ProgressChange Event

When you use the DoEvents function in a WebBrowser control ProgressChange event, you may receive the following application error:

There are two ways to work around this problem:

• Use a Timer to yield to the processor.
• Delegate the task to an ActiveX EXE component.

If you delegate the task to an ActiveX EXE component, the task can continue completely independent of your application, and the operating system takes care of multitasking and time slicing.

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

Steps to Reproduce Behavior

1. In Microsoft Visual Basic, create a new standard EXE project. Form1 is created by default.
2. Under Project, click Components, and then select a reference to Microsoft Internet Controls.
3. Add the WebBrowser control to your form.
4. On Form1, add two command button controls (named "Back" and "Forward") and one text box control.
5. In the code window of Form1, paste the following code:

   Private Sub Command1_Click()
   
       On Error Resume Next
       WebBrowser1.GoBack
   
   End Sub
   
   Private Sub Command2_Click()
   
       On Error Resume Next
       WebBrowser1.GoForward
   
   End Sub
   
   Private Sub Form_Load()
   
       WebBrowser1.Navigate2 "http://www.microsoft.com"
       Command1.Caption = "Go Back"
       Command2.Caption = "Go Forward"
   
   End Sub
   
   Private Sub WebBrowser1_DocumentComplete(ByVal pDisp As Object, URL As Variant)
   
       Text1.Text = WebBrowser1.LocationURL
   
   End Sub
   
   Private Sub WebBrowser1_ProgressChange(ByVal Progress As Long, ByVal ProgressMax As Long)
   
       DoEvents
   
   End Sub
   					

6. Run the project on a computer with Internet Explorer 5.5.
7. Browse through a few Web pages to build up the history list.
8. Click Back and Forward quickly to browse through the history. Eventually, you receive the above-mentioned error.

NOTE: This problem occurs both in Visual Basic Integrated Development Environment (IDE) mode and in the compiled version of the project.

For more information about developing Web-based solutions for Microsoft Internet Explorer, visit the following Microsoft Web sites: