XAF - Customize an XPO Business Model at Runtime

You can extend existing business classes without modifying their source code. For instance, when you work with an assembly that contains persistent classes.

This example modifies business classes declared in a separate project as follows:

• Adds an attribute (DefaultClassOptionsAttribute)
• Creates a simple persistent property (NewIntField)
• Creates reference and collection properties linked by an association (one-to-many relationship between PersistentObject1 and PersistentObject2 classes)

Implementation Details

1. Populate the AdditionalExportedTypes property with types from external storage to add them to the application.

   this.AdditionalExportedTypes.Add(typeof(MyXPOClassLibrary.PersistentObject1));
   this.AdditionalExportedTypes.Add(typeof(MyXPOClassLibrary.PersistentObject2));

2. Modify the added types as follows:

   • Call the AddAttribute method to add an attribute to an existing class.
     Note that by design you cannot dynamically add or remove the OptimisticLocking or DeferredDeletion attribute.

     ITypeInfo typeInfo1 = typesInfo.FindTypeInfo(typeof(PersistentObject1));
     typeInfo1.AddAttribute(new DevExpress.Persistent.Base.DefaultClassOptionsAttribute());

   • Call the CreateMember method to create a new simple persistent property.

     IMemberInfo memberInfo0 = typeInfo1.FindMember("NewIntField");
     if (memberInfo0 == null) {
         typeInfo1.CreateMember("NewIntField", typeof(int));
     }

   • Use both AddAttribute and CreateMember methods to create new reference and collection properties linked by an association.

     ITypeInfo typeInfo2 = typesInfo.FindTypeInfo(typeof(PersistentObject2));
     IMemberInfo memberInfo1 = typeInfo1.FindMember("PersistentObject2s");
     IMemberInfo memberInfo2 = typeInfo2.FindMember("PersistentObject1");
     if (memberInfo1 == null) {
         memberInfo1 = typeInfo1.CreateMember("PersistentObject2s", typeof(DevExpress.Xpo.XPCollection<PersistentObject2>));
         memberInfo1.AddAttribute(new DevExpress.Xpo.AssociationAttribute("PersistentObject1-PersistentObject2s", typeof(PersistentObject2)), true);
         memberInfo1.AddAttribute(new DevExpress.Xpo.AggregatedAttribute(), true);
     }
     if (memberInfo2 == null) {
         memberInfo2 = typeInfo2.CreateMember("PersistentObject1", typeof(PersistentObject1));
         memberInfo2.AddAttribute(new DevExpress.Xpo.AssociationAttribute("PersistentObject1-PersistentObject2s", typeof(PersistentObject1)), true);
     }

3. Call the RefreshInfo(Type) method to refresh metadata for the modified types.

   typesInfo.RefreshInfo(typeof(PersistentObject1));
   typesInfo.RefreshInfo(typeof(PersistentObject2));

Files to Review

• PersistentObject1.cs
• PersistentObject2.cs
• Module.cs

Documentation

• Ways to Add a Business Class
• Use Metadata to Customize Business Classes Dynamically
• Access Business Object Metadata
• How to create business classes at runtime based on predefined configurations or allow user to define custom members via the application UI
• How to define a custom member for a domain component (DC) at runtime?

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