5 Most Common Asked Questions When Using .Net RIA Services

If you're new here, you may want to subscribe to my RSS feed or become a fan of this blog on Facebook. Thanks for visiting!

From the comments on my previous articles on .Net RIA Services and from the search queries that lead to those articles, a pattern of a recurring set of questions showed up and I am sure that most .Net RIA Services enthusiasts face the same issues.

I will try and address a few of this issues in this post.

Oh, and please subscribe to my RSS Feed if you would like to read more on .Net RIA Services and other cool stuff I write about.

How to Exclude a Property with an Unsupported Type

I am sure this happened to most of you. You have a DomainService and you write a method to return one of your custom types that uses an Unsupported Type in .Net RIA Services. You build your solution and you get the following error.

Service operation named ‘GetUser’ does not conform to the required signature. Both return and parameter types must be an entity type or one of the predefined serializable types.

The error message is actually not that helpful as you tend to first think that there is something wrong with the method signature in the DomainService. But as it happens the issue is with the return type or the type of the parameter of that method.

The solution is really simple, all you have to do is add the ExcludeAttribute available in System.Web.DomainServices. For example in your class you have a reference to a MembershipUser in a property and you want to Exclude it your code would look like this

[Exclude]
public MembershipUser MyUser { get; set; }

The exclude attribute Indicates that an entity member should not exist in the code generated client view of the entity, and that the value should never be sent to the client.

How to Consume Services from Different Domains (URIs)

This is a question that came up in the comments of my Hello World .Net RIA Services example.

So the scenario is you have one client Silverlight application but multiple services that you want to consume, these can be on the same server or reside in different datacenters. This scenario can happen in delocalized units in large organizations where the client needs to figure out which server it should query for a specific info.

Luckily the guys behind .Net RIA Services thought about this and offer us a really simple way to achieve it. For each DomainService in our ASP.Net application a DomainContext is generated for the client application.

The generated class has 3 constructors, but the one we are interested in is the one that takes a Uri as a parameter.

/// <summary>
/// Constructor used to specify a data service URI.
/// </summary>
/// <param name="serviceUri">
/// The MyService data service URI.
/// </param>
public MyServiceContext(Uri serviceUri) :
       base(new HttpDomainClient(serviceUri))
{
}

Using this constructor we can specify which Server we want to connect to.

How to Return a String in a DomainService

This does not apply to strings only but for any Supported Type by the framework.

The solution is very simple, even though it took me a few minutes to figure it out. All you have to do is add the ServiceOperationAttribute to your method so that it’s generated in the DomainContext of the client application.

[ServiceOperation]
public string GetMyString()
{
   return "MyString";
}

How to Share a Class with the Silverlight Client

Sometimes we write utility classes that we would like available in our Business Tier as well as in our Presentation Tier. To achieve this in .Net RIA Services what we would do is append the .shared.cs suffix to the file that contains the class.

The generator automatically copies the content of that class that would be compiled both at the ASP.Net application as well as at the Silverlight Client level. Here is an excerpt from the .Net RIA Service overview:

This code can be compiled and executed on both the server and the client tiers. It is important to take a moment to consider why this is so. The .NET RIA Services framework automatically creates client proxy classes in the Silverlight project for all entities exposed by the server’s DomainService class. The framework preserves the entities’ namespace, name, and public properties.

When our sample server project compiles, the entity types are actually those generated by our Entity Framework database. However, when this code compiles on the client, these entity types are the generated client proxies.

In this way, the shared application logic is shared at the source level and compiled separately by the server and client projects. This makes it easy to author code once that can be used across tier boundaries.

What are all the Attributes Available in the .Net RIA Services Framework

Entity Attributes

These are attributes that can be applied to Entities used in your application:

ExcludeAttribute: Indicates that an entity member should not exist in the code generated client view of the entity, and that the value should never be sent to the client.

IncludeAttribute: When applied to an entity association, this attribute indicates that the framework should follow the association when non-null during serialization to send associated objects to the client. This attribute can also be used to specify member projections.

MetadataTypeAttribute: Used for associating a metadata class with the entity class.

Metadata Attributes

The Metadata attributes are used in the Metadata class associated with an entity:

AssociationAttribute: Used to mark an Entity member as an association

ConcurrencyCheckAttribute:This attribute is used to mark the members of a Type that participate in optimistic concurrency checks.

CustomValidationAttribute: Validation attribute that executes a user-supplied method at runtime.

DataTypeAttribute: Allows for clarification of the DataType represented by a given property (such as Password vs URL)

DisplayAttribute: DisplayAttribute is a general-purpose attribute to specify user-visible globalizable strings for types and members. The string properties of this class can be used either as literals or as resource identifiers into a specified ResourceType

DisplayColumnAttribute: Sets the display column, the sort column, and the sort order for when a table is used as a parent table in FK relationships.

DisplayFormatAttribute: Allows overriding various display-related options for a given field. The options have the same meaning as in BoundField.

FilterUIHintAttribute: An attribute used to specify the filtering behavior for a column.

KeyAttribute: Used to mark one or more entity properties that provide the entity’s unique identity

RangeAttribute: Used for specifying a range constraint

RegularExpressionAttribute: Regular expression validation attribute

RequiredAttribute: Validation attribute to indicate that a property field or parameter is required.

StringLengthAttribute: Validation attribute to assert a string property, field or parameter does not exceed a maximum length

TimestampAttribute: This attribute is used to mark a Timestamp member of a Type.

UIHinAttribute: Attribute to provide a hint to the presentation layer about what control it should use.

ValidationAttribute: Base class for all validation attributes.

DomainService Attributes

Note that most of the CRUD operations can be inferred from the name of the method and the is not need to use the attribute.

AuthorizationAttribute: Identifies the permissions required to invoke a DomainOperationEntry.

CustomAttribute: Attribute applied to a DomainService method to indicate that it is a custom method.

DeleteAttribute: Attribute applied to a DomainService method to indicate that it is a delete method.

IgnoreOperationAttribute: Attribute applied to a DomainService method to indicate that code generators should not infer a method as a domain operation.

InsertAttribute: Attribute applied to a DomainService method to indicate that it is an insert method.

MetadataProviderAttribute: Apply this attribute to a DomainService to specify one or more custom TypeDescriptionProvider Types that should be registered for all entity types exposed by the DomainService.

QueryAttribute: Attribute applied to a DomainService method to indicate that it is a query method.

RequiresAuthenticationAttribute: Identifies the authentication requirements needed to invoke a DomainOperationEntry.

RequiresRolesAttribute: Identifies the roles required to invoke a DomainOperationEntry.

ResolveAttribute: Attribute applied to a DomainService method to indicate that it is a resolve method.

ServiceOperationAttribute: Attribute applied to a DomainService method to indicate that it is a service operation.

UpdateAttribute: Attribute applied to a DomainService method to indicate that it is an update method.

Hope this helps.

Hatim