I have an ASP.NET MVC solution and also a WCF service for data access. In my WebUI I have some enums like this:
public enum CompanyColumsEnumViewModel
{
CompanyName,
CompanyPostCode,
CompanyCity
}
This enum allows me to perform a search based on specific columns. For example: searching for '2000' in the CompanyPostCode field.
When a user submit a search formular, I call my service and I pass several parameters like this:
var companies = _requestServiceClient.GetCompanies(term, column);
Where term = '2000' and column = 'CompanyPostCode'
My question is what is the best:
pass column as en enumeration in the web service? (1)
pass column as simple string in my web service? (2)
(1) IEnumerable< Company> GetCompanies(string term, CompanyColumsEnumViewModel column)
(2) IEnumerable< Company> GetCompanies(string term, string column)
If I work with enumerations I have to declare these enumerations on both side: one in my WebUI and one in my web service?
Thanks.
If your enum is part of your ServiceContract (as in it exists as a parameter) then you need to attribute it up as a DataContract:
[DataContract]
public enum CompanyColumsEnumViewModel
{
[EnumMember]
CompanyName,
[EnumMember]
CompanyPostCode,
[EnumMember]
CompanyCity
}
Then, you can discover this in a service reference on the client side. This, I think, would be prefered to a string column.
You can declare your enum as normal in a separate file. Custom objects can explicitly be given defined data contracts and members, but if the enum is exposed as a parameter in a WCF service, then WCF is smart enough to go back and serialize it out to the WSDL itself.
This works the same for all types. If you have a class as a parameter in a WCF method, and that class has this enum as a property, then the class and the enum would both be exposed through the WSDL, and would be auto-generated on the client.
Related
Scenario A: Suppose you have several databases on the same SQL Server/SQL Azure instance sharing the exact same structure, where the database names are convention based, like db001, db002, ... and a single RESTier service must be able to address the correct database for each REST call, depending on some characteristic to be provided on the request header or on the URI path or query string.
Scenario B: A single RESTier service must be able to address more than one connection string, defined on the web.config file, depending on some characteristic to be provided on the request.
In both scenarios the base issue is the same, a single RESTier service to be able to address requests for more than one database, where the client must submit on each request a hint to the database to be used, a typical multitenant scenario. I'm using RESTier version 0.6 and the entity sets are automatically exposed from a Entity Framework model:
public class Entities : EntityFrameworkApi<SalesEntities> {
Question is, how would you advise to implement this kind of multi-tenant scenarios?
You could use a parameterized routePrefix like below and parse that part of the URL (HttpContext.Current.Request.RawUrl).
config.MapRestierRoute<Entities>("EntitiesApi", "api/{entitiesConfig}", new RestierBatchHandler(server));
Retrieve the correct connectionString from your Web.config and use that to create the DbContext:
Match match = Regex.Match(HttpContext.Current.Request.RawUrl, #"/api/(?<entitiesConfig>[A-Za-z0-9\-]+)/", RegexOptions.IgnoreCase);
string entitiesConfig = "DefaultEntitiesContext";
if (match.Success)
entitiesConfig = match.Groups["entitiesConfig"];
string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings[entitiesConfig].ConnectionString;
var db = new SalesEntities(connectionString);
For your scenario, I think you will have two DbContext, each one connect to one DB instance, then will something like this will work for you?
In the configure method, we call MapRestierRoute twice, and each one will handle one DbContext with different route prefix, and when user initiate the request, the request URL will contain prefix and will auto route to related DB instance.
config.MapRestierRoute>( "TrippinApi", "api/TrippinA", new RestierBatchHandler(server));
config.MapRestierRoute>( "TrippinApi", "api/TrippinB", new RestierBatchHandler(server));
Let me if you have any issues with this.
I am writing a Web API that clients can make requests to to return data in XML format. I am implementing this in .NET using Enterprise Foundation and MVC4.
I am struggling a bit with how to only return a subset of some fields from my Models in my Controllers.
For arguments sake, lets say I have a Product model that contains attributes "Id", "Name", "Price" and "Actual Cost" (I am using an example from http://www.asp.net/web-api/overview/creating-web-apis/using-web-api-with-entity-framework/using-web-api-with-entity-framework,-part-6)
I need to expose a Web API for clients to query a specific Product to get its name and price, but in this response I don't want to return the "Actual Cost" property (because this is our secret).
Now in the link I provide this is exactly the problem they are attempting to solve by the use of DTO's (they define a DTO called ProductDTO that contains only the subsets I want to return). I have implemented this solution and I am indeed now able to return only the fields I specify in the DTO.
The problem is that the naming used for the returned entity in XML is now ProductDTO rather than Product, i.e. the returned XML is
{"ProductDTO":[{"Id":1,"Name":"Tomato Soup","Price":1.39}, {"Id":3,"Name":"Yo yo","Price":6.99]}
rather than
{"Product":[{"Id":1,"Name":"Tomato Soup","Price":1.39}, {"Id":3,"Name":"Yo yo","Price":6.99]}
That means that all of our clients currently using our API and expects a "Product" to be returned will now get a "ProductDTO" returned, which means that they will have to make changes to their code and which is unacceptable. I need to provide them with a "Product" with only the relevant set of sub-fields as they are currently getting. How do I achieve this? I cannot simply "ignore" a data member as suggested in prevent property from being serialized in web api because I also have some API cases where I indeed DO need to return ALL the attributes and not only a subset.
Just some background: We have an existing API server interface that was written in Ruby on Rails and we are now moving this over to C# and .NET MVC4. We also have a bunch of client applications already interfacing to our existing, older, Ruby on Rails API Server and we don't want clients to make any changes to their code. We are simply moving our API server code over from Ruby on Rails to C#. In Ruby on Rails I was simply able to apply a filter to the XML Serializer when I need to only return a subset of attributes on certain calls.
If you want to continue down the DTO route that you have started, which IMHO is a good idea as it gives you control of what you export without polluting your internal classes with export specific stuff, you can add a DataContract attribute to your ProductDTO class.
[DataContract(Name="Product")]
public class ProductDTO
{
[DataMember]
public int Id {get;set;}
[DataMember]
public string Name {get;set;}
}
The default XML formatter used in Web API is the DataContractSerializer.
You can read more about this here
Suppose you have a class like
public class product
{
public string Name{get; set;}
..
}
and you don't want to appear it in the response you can just use [XMLIgnore] attribute
[XMLIgnore]
public string Name{get; set;}
hopes this helps.
In the examples for ServiceStack I don't see a single application that is ASP.NET MVC website first and then made ServiceStack service second.
Let's take a very simple ASP.NET MVC web application that renders products through Views. It uses controllers, views, models and viewmodels.
Let's say we have a model of Product which gets persisted into a document DB. Let's assume we have a viewmodel of ProductViewModel which gets mapped from Product and display within MVC Razor View/PartialView.
so this is a web side of things..now let's assume we want to add a service returning products to various clients like the Windows 8 applications.
Should the request/response classes be completely disconnected from what we already have? Our ProductViewModel might already contain everything we want to return from the service.
Since we already have Product (model class) we can't have another Product class in the API namespace..well we could but that makes things unclear and I'd like to avoid that.
So, should we introduce standalone ProductRequest class and ProductRequestResponse (inherits ProductViewModel) class in the API namespace?
Like so ProductRequestResponse : ProductViewModel?
What i'm saying is, we already have the Model and ViewModel classes and to construct Request and Response classes for the SS service we would have to create another two files, mostly by copying everything from the classes we already have. This doesn't look DRY to me, it might follow the separation of concerns guidelines but DRY is important too, actually more than separating everything (separating everything leads to duplication of code).
What I would like to see is a case where a web application has already been made, it currently features Models and ViewModels and returns the appropriate Views for display on the Web but can be extended into a fully functional service to support programmatic clients? Like AJAX clients etc...with what we already have.
Another thing:
If you take a look at this example https://github.com/ServiceStack/ServiceStack.Examples/blob/master/src/ServiceStack.MovieRest/MovieService.cs
you will see there is Movie Request class and Movies Request class (one for single movie request, the other one for a list of movies). As such, there are also two services, MovieService and MoviesService, one dealing with requests for a single movie, the other one for a genre of movies.
Now, while I like SS approach to services and I think it is the right one, I don't like this sort of separation merely because of the type of request. What if I wanted movies by director? Would I be inventing yet another request class having a Director property and yet another service (MoviesByDirector) for it?
I think the samples should be oriented towards one service. Everything that has to deal with movies need to be under one roof. How does one achieve that with ServiceStack?
public class ProductsService : Service
{
private readonly IDocumentSession _session;
private readonly ProductsHelperService _productsHelperService;
private readonly ProductCategorizationHelperService _productCategorization;
public class ProductRequest : IReturn<ProductRequestResponse>
{
public int Id { get; set; }
}
// Does this make sense?
// Please note, we use ProductViewModel in our Views and it holds everything we'd want in service response also
public class ProductRequestResponse : ProductViewModel
{
}
public ProductRequestResponse GetProducts(ProductRequest request)
{
ProductRequestResponse response = null;
if (request.Id >= 0)
{
var product = _session.Load<Product>(request.Id);
response.InjectFrom(product);
}
return response;
}
}
The Service Layer is your most important Contract
The most important interface that you can ever create in your entire system is your external facing service contract, this is what consumers of your service or application will bind to, i.e. the existing call-sites that often won't get updated along with your code-base - every other model is secondary.
DTOs are Best practices for remote services
In following of Martin Fowler's recommendation for using DTOs (Data Transfer Objects) for remote services (MSDN), ServiceStack encourages the use of clean, untainted POCOs to define a well-defined contract with that should kept in a largely implementation and dependency-free .dll. The benefits of this allows you to be able to re-use typed DTOs used to define your services with, as-is, in your C#/.NET clients - providing an end-to-end typed API without the use of any code-gen or other artificial machinery.
DRY vs Intent
Keeping things DRY should not be confused with clearly stating of intent, which you should avoid trying to DRY or hide behind inheritance, magic properties or any other mechanism. Having clean, well-defined DTOs provides a single source of reference that anyone can look at to see what each service accepts and returns, it allows your client and server developers to start their work straight away and bind to the external service models without the implementation having been written.
Keeping the DTOs separated also gives you the freedom to re-factor the implementation from within without breaking external clients, i.e. your service starts to cache responses or leverages a NoSQL solution to populate your responses with.
It's also provides the authoritative source (that's not leaked or coupled inside your app logic) that's used to create the auto-generated metadata pages, example responses, Swagger support, XSDs, WSDLs, etc.
Using ServiceStack's Built-in auto-mapping
Whilst we encourage keeping separate DTO models, you don't need to maintain your own manual mapping as you can use a mapper like AutoMapper or using ServiceStack's built-in Auto Mapping support, e.g:
Create a new DTO instance, populated with matching properties on viewModel:
var dto = viewModel.ConvertTo<MyDto>();
Initialize DTO and populate it with matching properties on a view model:
var dto = new MyDto { A = 1, B = 2 }.PopulateWith(viewModel);
Initialize DTO and populate it with non-default matching properties on a view model:
var dto = new MyDto { A = 1, B = 2 }.PopulateWithNonDefaultValues(viewModel);
Initialize DTO and populate it with matching properties that are annotated with the Attr Attribute on a view model:
var dto = new MyDto { A=1 }.PopulateFromPropertiesWithAttribute<Attr>(viewModel);
When mapping logic becomes more complicated we like to use extension methods to keep code DRY and maintain the mapping in one place that's easily consumable from within your application, e.g:
public static class MappingExtensions
{
public static MyDto ToDto(this MyViewModel viewModel)
{
var dto = viewModel.ConvertTo<MyDto>();
dto.Items = viewModel.Items.ConvertAll(x => x.ToDto());
dto.CalculatedProperty = Calculate(viewModel.Seed);
return dto;
}
}
Which is now easily consumable with just:
var dto = viewModel.ToDto();
If you are not tied specifically to ServiceStack and just want "fully functional service to support programmatic clients ... with what we already have", you could try the following: Have your controllers return either a ViewResult or a JsonResult based on the request's accept header - Request.AcceptTypes.Contains("text/html") or Request.AcceptTypes.Contains("application/json").
Both ViewResult and JsonResult are ActionResult, so the signature of actions remains the same, and both View() and Json() accept a ViewModel. Furthermore, if you have a ControllerBase you can make a base method (for example protected ActionResult RespondWith(Object viewModel)) which calls either View() or Json() so the change to existing code is minimal.
Of course, if your ViewModels are not pure (i.e. have some html-specific stuff or you rely on some ViewBag magic) then it's a little more work. And you won't get SOAP or other binding types provided by ServiceStack, but if your goal is to support a JSON data interface with minimal code changes to the existing MVC app then this could be a solution.
Lp
My system consists of a back-end part, written in Java, exposing a set of web services which are defined contract-first using WSDL and XSD. Among the data transported over the web services are a large set of product types (they are different kinds of bank accounts, to be precise). Our front-end is a Grails web application. It uses and exposes the data and operations hosted by the back-end. The front-end has no database on its own for security reasons; all data is stored on the back-end. Pretty standard architecture.
Now, the set of products is large, growing, and volatile. Each product type has to be CRUD-ed on the web application user interface. It would be lovely if I could tell Grails to use the XSD specifications of the product types as domain types, and generate views and controllers for them.
I have not found a solution for this puzzle yet, even after extensive experiments and lots of web browsing. I have about a year's worth of professional experience with Grails. Any help or ideas would be appreciated.
Some details:
A product type is a simple POJO data carrier. Some simplified examples:
package jaxbgenerated;
public class Product1 {
protected Account from;
protected Account to;
protected String name;
// + getters and setters
}
public class Product2 {
protected List<Account> accounts;
protected String name;
// + getters and setters
}
public class Account {
protected String id1;
protected String id2;
// + getters and setters
}
Note that "Account" is not a product type but it is a JAXB-generated type. Products can contain such in addition to properties of simple data types like String, int and Date but they never contain other product types.
The end result I am aiming for is a Grails-generated form where a user can edit a Product1 instance with nested forms for editing its constituent Accounts. And likewise for Product2.
My idea is to first manually code a Grails domain class for each JAXB-generated type:
//in grails-app/domain:
import utilities.Copier
class Product1 extends jaxbgenerated.Product1 {
Product1(jaxbgenerated.Product1 jaxb) {
Copier.copy(jaxb, this)
}
static constraints = {
}
}
There is a bit of boilerplate code here but nothing more than I can live with. The Copier.copy() function is (I think) needed to convert a jaxbegenerated.Product instance fetched from the back-end to a Product1 instance which can be used in Grails. It recursively looks for jaxbgenerated properties in the jaxb source, and copies their values to the corresponding Grails domain type. The constructor is invoked from a layer that fetches data from the back-end.
I can use the constraints block to manually add semantic constraints where needed, e.g. that the "from" and "to" accounts are not the same.
Next, I generate controllers and views for all the Grails domain classes thus constructed, and run the application. And get a stack of exceptions:
Caused by MappingException: Could not determine type for: Account, at table:
product1_type, for columns: [org.hibernate.mapping.Column(from)]
I think the trouble here is that Product1's "from" and "to" properties are not of type Account but of type jaxbgenerated.Account.
I have tried different approaches but to no avail. Some notes:
As I said, all data storage happens on my back-end, so I do not need
the GORM/Hibernate aspect of Grails. Therefore I tried adding
"static mapWith = "none" to the domain classes but that did not
help.
I tried explicitly telling Hibernate the type of the Accounts
in Product1 by adding "static mapping = { from type: Account }" but
that did not work either.
Any help or ideas would be appreciated.
/Jan Reher, Systematic A/S, Denmark
I think you have do write a dababase plugin similar in concept to this simpledb
In my ASP.NET MVC project, my actions typically call a Service layer to get data. I use the same dozen or so POCOs for all my models. I also plan on using the Service layer in console applications and maybe expose a web api at some point.
To make my database operations more efficient, my service layer only hydrates the properties in the model that are relevant to the particular method (which at this point is mostly driven by the needs of my controller actions).
So for example I might have a class Order with properties Id, Name, Description, Amount, Items. For a given service call I might only need to populate Id, Name, Items. A consumer of that service won't necessarily know that Amount is 0 only because it didn't populate the property.
Similarly, the consumer won't know whether Items is empty b/c there actually aren't any items, or whether this particular service method just doesn't populate that property.
And for a third example, say one of my views displays an ItemCount. I don't want to fully populate my Items collection, I just need an additional property on my "model". I don't want to add this property to my POCO that other service methods will be using because it's not going to be populated anywhere else.
So the natural solution is to make a POCO designed specifically for that method with only those 3 properties. That way the consumer can know that all properties will be populated with its real values. The downside to this is that I'll end writing tons of similarly shaped models.
Any advice on which method works best?
You could use Nullable Types to indicate the missing properties with a null.
For example:
class Order {
public int Id {get;set;}
public string Name {get;set;}
public string Description {get;set;}
public decimal? Amount {get;set;}
public List<Item> Items {get;set;}
}
And then if Items == null, it wasn't set. If it's an empty new List<Item>(), it's set but empty. Same for Amount. If Amount.HasValue == false, it wasn't set. If Amount.Value is 0.0d, it's set and the item is free.
Why don't you use LINQ projection?
One service method does something like:
return DbContext.Orders.Select(o => new { Id = o.Id, Name = o.Name, Description = o.Description });
while the other service method does something like:
return DbContext.Orders.Select(o => o);
I'm not sure how your application is architected, but this may be a way around creating 100's of POCO's.
Hope this helps! Good luck.
You could pass in a selector Func that returns dynamic:
public IEnumerable<dynamic> GetOrders(Func<Order, dynamic> selector) { ... }
I'm not sure how you are accessing data, but the following shows how this would work using a List<T>:
class Program
{
static void Main(string[] args)
{
var service = new Service();
var orderNames = service.GetOrders(o => new { o.Name });
foreach (var name in orderNames)
Console.WriteLine(name.Name);
Console.ReadLine();
}
}
public class Service
{
private List<Order> _orders = new List<Order>
{
new Order { Id = 1, Name = "foo", Description = "test order 1", Amount = 1.23m },
new Order { Id = 2, Name = "bar", Description = "test order 1", Amount = 3.45m },
new Order { Id = 3, Name = "baz", Description = "test order 1", Amount = 5.67m }
};
public IEnumerable<dynamic> GetOrders(Func<Order, dynamic> selector)
{
return _orders.Select(selector);
}
}
public class Order
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public decimal Amount { get; set; }
}
The use of nullable values is a good solution, however it has the downside you have no way to matk required fields. That is you cannot use a required attribute on any property. So if there is field that is obligatory in some views you have no way to represent it.
If you don't need required fileds validation this is ok. Otherwise, you need a way to represent which fileds are actually used, and then to write a custom validation provider.
A simple way to do this is to use a "Mask" class with the same property names of the original class, but with all fields boolean: a true values means the field is in use.
I used a similar solution in a system where the properties to be shown are configured in a configuration files...so it was the unique option for me since I had no possibility to represent all combination of properties. HOWEVER, I used the "Mask" class also in the View, so I was able to do all the job with just one View..with a lot of ifs.
Now if your 150 service methods and probably about 150 Views...are all different, then maybe it is simpler to use also several classes ...that is in the worst case 150 classes..the extra work to write them is negligible if compared to the effort of preparing 150 different Views.
However this doesnt mean you need 150 POCO classes. You might use an unique POCO class that is copied into an adequate class just into the presentation Layer. The advantage of this approach is that you can put different validation attributes on the various classes and you don't need to write a custom Validation provider.
Return the entire POCO with nullable types as mentioned by #sbolm. You can then create a ViewModel per MVC page view that receives a model with the specific properties it needs. This will take more performance (insignificant) and code, but it keeps your service layer clean, and keeps your views "dumb" in that they are only given what they need and have no direct relation to the service layer.
I.e. (example class from #sbolm)
class Order {
public int Id {get;set;}
public string Name {get;set;}
public string Description {get;set;}
public decimal? Amount {get;set;}
public List<Item> Items {get;set;}
}
// MVC View only needs to know the name and description, manually "map" the POCO properties into this view model and send it to the view
class OrderViewModel {
public string Name {get;set;}
public string Description {get;set;}
}
I would suggest that instead of modifying the models or creating wrapper models, you have to name the service methods such that they are self-explanatory and reveals the consumer what they returns.
The problem with the nullable approach is it makes the user to feel that the property is not required or mandatory and they try inserting instances of those types without setting those properties. Is it won't be bad having nullables every-where?
It won't be a good approach to change the domain models since all you want is just to populate some of the properties instead of that you create service with names and descriptions that are self-explanatory.
Take the Order class itself as the example, say one service method returns the Order with all the items and the other one returns only the details of the Order but not the items. Then obviously you may have to create two service methods GetOrderItems and GetOrderDetail, this sounds so simple, yes it is! but notice the service method names itself tells the client what it is going to return. In the GetOrderDetail you can return an empty items or null (but here I suggest a null) that doesn't matter much.
So for new cases you don't need to frequently change the models but all you got to do is add or remove the service methods and that's fine. Since you are creating a service you can create a strong documentation that says what method does what.
I would not performance optimize this to much unless you realy get performance problems.
I would only distinguish between returning a flat object and an object with a more complete object graph.
I would have methods returning flat objects called something like GetOrder, GetProduct.
If more complete object graphs are requested they would be called : GetOrderWithDetails.
Do you use the POCO classes for the typed views? If yes: try to make new classes that serve as dedicated ViewModels. These ViewModels would contain POCO classes. This will help you keeping the POCO classes clean.
To expand on the nullable idea, you could use the fluentvalidation library to still have validation on the types dependent on whether they are null or not. This would allow you to have a field be required as long as it was not null or any other validation scheme you can think of. Example from my own code as I had a similar requirement:
Imports FluentValidation
Public Class ParamViewModelValidator
Inherits AbstractValidator(Of ParamViewModel)
Public Sub New()
RuleFor(Function(x) x.TextBoxInput).NotEmpty.[When](Function(x) Not (IsNothing(x.TextBoxInput)))
RuleFor(Function(x) x.DropdownListInput).NotEmpty.[When](Function(x) Not (IsNothing(x.DropdownListInput)))
End Sub
End Class