PRB: Common Dialog Open: Err=20476 Buffer lpstrFile Too Small

   CMDialog1.MaxFileSize = 2048
				

MORE INFORMATION

You can set the Flags property of the Common Dialog to &H200&, or OFN_ALLOWMULTISELECT, to allow multiple selections in the File Name list box. You can select more than one file at run time by pressing the SHIFT key and using the UP and DOWN ARROW keys to select the desired files. The FileName property returns a string containing the names of all selected files. The names in the string are delimited by spaces.

Steps to Reproduce Behavior

1. Start a new project in Visual Basic. Form1 is created by default.
   
   If the common dialog CMDIALOG.VBX file is not automatically loaded by AUTOLOAD.MAK in Visual Basic, load CMDIALOG.VBX as follows: choose Add File from the File menu, and select CMDIALOG.VBX from your WINDOWS\SYSTEM directory.
2. Add a Common Dialog custom control to Form1.
3. Add the following to the Form Load event code:

      Sub Form_Load ()
         CMDialog1.Flags = &H200&   ' Allows selection of more than 1 file.
         CMDialog1.Filter = "ALL|*.*"   ' File types to list in file box.
         ' CMDialog1.MaxFileSize = 2048  ' Add this to correct the behavior.
         CMDialog1.Action = 1      ' Action 1 = standard Open file dialog box
      End Sub
   
   						

4. Start the program (or press F5). Select 20 or files at once by selecting the first article then pressing SHIFT+END. That highlights all files down to the last article. Choose the OK button. The following error message displays if the number of characters in all the selected file names, plus one character for each file name, exceeds 256:
   The buffer at which the member lpstrFile points is too small.
   If error trapping (On Error Goto) is on, the Err function reports error number 20476. In the Visual Basic environment, if you press F5 or choose Continue from the Run menu after getting this error, you get the following error message:
   Invalid filename.

To improve this behavior, add the CMDialog1.MaxFileSize=2048 statement before setting the CMDialog1 Action property to 1. This increases the maximum allowed returned string size from 256 to 2048.