Error Reading Form: Class XXXX not found
When opening a form (typically on a PC other than the one it was originally produced on), a dialog box is displayed showing the following error:
Error Reading Form
Class XXXX not found. Ignore the error and continue? NOTE: Ignoring the error may cause components to be deleted or property values to be lost.
where: XXXX is the name of a component.
The form is using an Active-X component which is not available.
Typically this indicates that the Delphi was originally written on one pc where an Active-X component was available but is being recompiled on a PC where the component is not available.
DO NOT CLICK "IGNORE". If you ignore the error then the component is replaced by a panel, and thus all functionality associated with it will be lost. Instead click "Cancel".
- Identify the Active-X component which is missing. This is
the name given in the error message.
Class TWebBrowser not found.
indicates that the active-X control "TWebBrowser" is missing.
- In some cases the Active-X component may be available on the
PC but not imported into Delphi.
For example TWebBrowser can be made available by importing "Microsoft Internet Controls" - full instructions for TWebBrowser can be found here.
In general the procedure is to:
- On the "Component" menu select "Import ActiveX Control..."
- Scroll through each control listed until the missing control is listed against "Class names", this is the control that you will need to install.
- Once you have found it click the "Install..." button (not the "Create Unit" button), and confirm any prompts which follow.
- Restart Delphi and reload the offending project.
- If the Active-X component is not available on the local PC then you will need to identify where it originally came from and arrange to obtain a (licensed) copy of it.
These notes are believed to be correct for Delphi 6 and Delphi 7, and may apply to other versions as well.
About the author: Brian Cryer is a dedicated software developer and webmaster. For his day job he develops websites and desktop applications as well as providing IT services. He moonlights as a technical author and consultant.