Deleting Site Columns and Content Types Programmatically

Question

I have a feature that adds two site columns to a content type on activation. On deactivation it's supposed to delete them, but I'm getting the following error: "Site columns which are included in content types or on lists cannot be deleted. Please remove all instances of this site column prior to deleting it."

        SPWeb web = properties.Feature.Parent as SPWeb;
        SPContentType cType = web.ContentTypes[Constants.ClientContentTypeName];

        cType.FieldLinks.Delete(Constants.DebtMgmtClientID);
        cType.FieldLinks.Delete(Constants.DebtMgmtCompanyID);
        cType.Update();

        web.Fields.Delete(Constants.DebtMgmtClientID); // This line throws the error
        web.Fields.Delete(Constants.DebtMgmtCompanyID);

I guess I'm doing it in the wrong order. Can anyone help?

Thanks in advance.

Answer 1

You need to remove the Column from every content type that may be using it. For example: If you created a column, and bound it to the Document content type, and pushed it down to all of its children, you'll need to remove it from every one of those children before deleting the custom column.