Brian Cryer

  

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Delphi Troubleshooting

Error Reading Form: Class XXXX not found

Symptom:

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.

Cause:

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.

Remedy:

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".

  1. Identify the Active-X component which is missing. This is the name given in the error message.

    For example:

    Class TWebBrowser not found.

    indicates that the active-X control "TWebBrowser" is missing.

  2. 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:

    1. On the "Component" menu select "Import ActiveX Control..."
    2. Scroll through each control listed until the missing control is listed against "Class names", this is the control that you will need to install.
    3. Once you have found it click the "Install..." button (not the "Create Unit" button), and confirm any prompts which follow.
    4. Restart Delphi and reload the offending project.
  3. 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.