FIX: Unexpected behavior occurs when a user selects a folder that has a long path in a Folder dialog box in a .NET Framework 1.1 Windows Forms application

The FolderBrowserDialog class is included in the Microsoft Windows Forms Library that is included with the Microsoft .NET Framework 1.1. You can use the FolderBrowserDialog class to display a folder selection dialog box that is named Folder in a Windows Forms application.

However, in the Folder dialog box, if a user selects a folder that has more than 130 characters in its full path, the user may experience one of the following:

• The user receives a NullReferenceException error message.
• The user receives an OutofRangeException error message.
• The user receives no error message and the application stops responding (hangs).
• The user receives no error message and the application quits unexpectedly (crashes).

This behavior occurs because the heap is overwritten in the FolderBrowserDialog class implementation.

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section of this article.

For additional information about the terminology that is used to describe Microsoft product updates, click the following article number to view the article in the Microsoft Knowledge Base:

Steps to reproduce the behavior

1. Create a folder that has a full path that is more than 130 characters long. For example, in the root folder, create a folder that is named 0000000001000000000100000000010000000001000000000100000000010000000001000000000100000000010000000001000000000100000000010000000001.
   
   If your root folder is named C, the path of this folder is the following:
   C:\0000000001000000000100000000010000000001000000000100000000010000000001000000000100000000010000000001000000000100000000010000000001
2. In Microsoft Visual Studio .NET 2003, use C# to create a Windows Forms Application project. By default, a form that is named Form1 is created.
3. Add a Button control to the Form1 form. By default, a Button control that is named Button1 is created.
4. Create a Click event handler for the Button1 control.
5. Implement the button1_Click event handler by using the following code:

   private void button1_Click(object sender, System.EventArgs e)
   {
       FolderBrowserDialog fbd;
       fbd = new FolderBrowserDialog();
       fbd.ShowDialog();
   }

6. Build and then run the application.
7. Click Button1. The Folder dialog box appears.
8. In the Folder dialog box, do the following:
   1. Click the folder that you created in step 1.
   2. Click a different folder.
9. Repeat step 8 many times.

The behavior that the "Symptoms" section describes occurs when you repeatedly select a folder that has more than 130 characters in its full path.