How to: Implement File Data Properties

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This topic demonstrates how to implement a business class with a file data property and a file collection property. For this purpose, the Resume class, which is used to store and manage an employee's resume information, is implemented. It has three properties: File, Contact and Portfolio. The File property provides a file, the Contact property contains a reference to the Contact class, and the Portfolio property returns a collection of the employee's files.

To add a file data type property and a file collection property to a business object, you should use a type that implements the IFileData interface and one that applies the FileAttachment attribute. In this instance, the FileAttachmentsWindowsFormsModule and/or FileAttachmentsAspNetModule modules should be added to your WinForms and/or ASP.NET Web module projects respectively. In this instance, the FileAttachmentsWindowsFormsModule and/or FileAttachmentsBlazorModule modules should be added to your WinForms and/or Blazor module projects respectively. These modules contain Property Editors for IFileData type properties, and Controllers with Actions that are necessary for file manipulation. For details, refer to the File Attachments Module Overview topic.

To add the FileAttachmentsWindowsFormsModule and/or FileAttachmentsAspNetModule module(s) to the application, invoke the Module Designer for the WinForms and/or ASP.NET module project(s), drag the corresponding item from the Toolbox to the Designer's Required Modules section, and rebuild the solution.

To add the FileAttachmentsWindowsFormsModule and/or FileAttachmentsBlazorModule module(s) to the application, install the DevExpress.WindowsDesktop.XAF.FileAttachment.Win and/or DevExpress.ExpressApp.FileAttachment.Blazor NuGet packages to the WinForms and/or Blazor module project(s). Add the File Attachment Module to the platform-specific module's RequiredModuleTypes collection. (For more information, refer to the Reuse Implemented Functionality topic.) Rebuild the solution.

The following code demonstrates a Resume business object.

public class Resume : BaseObject {
   public Resume(Session session) : base(session) {}
   private Contact contact;
   private FileData file;
   [Aggregated, ExpandObjectMembers(ExpandObjectMembers.Never)]
   public FileData File {
      get { return file; }
      set {
         SetPropertyValue(nameof(File), ref file, value);
   public Contact Contact {
      get { 
         return contact;
      set {
         SetPropertyValue(nameof(Contact), ref contact, value);
  [Aggregated, Association("Resume-PortfolioFileData")]
  public XPCollection<PortfolioFileData> Portfolio {
     get { return GetCollection<PortfolioFileData>(nameof(Portfolio)); }
public class PortfolioFileData : FileAttachmentBase {
   public PortfolioFileData(Session session) : base(session) {}
   private DocumentType documentType;
   protected Resume resume;
   [Persistent, Association("Resume-PortfolioFileData")]
   public Resume Resume {
      get { return resume; }
      set { 
         SetPropertyValue(nameof(Resume), ref resume, value); 
   public override void AfterConstruction() {
      documentType = DocumentType.Unknown;
   public DocumentType DocumentType {
      get { return documentType; }
      set { SetPropertyValue(nameof(DocumentType), ref documentType, value);}
public enum DocumentType { SourceCode = 1, Tests = 2, Documentation = 3, 
   Diagrams = 4, ScreenShots = 5, Unknown = 6 };

To create a collection of an employee's files, the Resume class has the Portfolio property of the XPCollection<PortfolioFileData> type. The PortfolioFileData class is inherited from the FileAttachmentBase class, which in turn, uses the FileAttachment interface. The FileAttachmentBase class, as well as the FileAttachment attribute, is from the Business Objects Library.

The PortfolioFileData class has the DocumentType property that specifies the portfolio file type. This property is initialized in the AfterConstruction method override. The PortfolioFileData class also stores a reference to a Resume object in its Resume property.

The following images show the Resume Detail View in WinForms and ASP.NET Web applications.The following images show the Resume Detail View in WinForms and Blazor applications.




See Also