Our WCF services return Datasets to the webserver,
In the new .NET web site we are going to use MVC 5. Since MVC 5 framework works really well with known business objets (validation framework etc.), we need to convert Datasets to known business objects in the Model classes.
We tried following conversion,
public List<Category> GetCategories()
{
List<Category> cats = new List<Category>();
DataTable dt = //get data table from the dataset;
foreach (DataRow row in dt.Rows)
{
Category cat = new Category();
cat.CategoryID = int.Parse(row["CategoryID"].ToString());
cat.CategoryName = row["CategoryName"].ToString();
cat.Description = row["Description"].ToString();
cat.Picture = GetBytes(row["Picture"].ToString());
cats.Add(cat);
}
return cats;
}
Assume that we retrieve and unpack the data table.
Will this be an expensive conversion if there are 100s' of request per second accessing this code block?
What would be a better way to test the performance under load?
Or is there a better approach to solve this problem?
Really appreciate any help on this.
I would not worry about the time it takes to convert the DataSet to domain objects since it's going to be a fraction of the remote call to get the data through a remote service.
However, for result sets that rarely change I would recommend adding caching around the resolved domain objects to avoid the conversion, but more importantly avoid the WCF call and subsequent DB call.
Related
Which is the best approach for updating multiple records at a time using ASP.NET Web API and OData against an Entity Framework database?
Let's suppose we have a table in our database with a "State" field, and we want to do something similar to this SQL statement: "UPDATE Table set State = 1". Should I do a loop with GET and PUT for each record? I do not like it at all, I guess it must be a better way to accomplish this.
Thank you
It looks like you can't do this natively in OData, but there is one approach that will definitely work; just use a native Web API action to perform the update.
E.g.
[HttpPut]
[Route("resources/state")]
public IHttpActionResult UpdateState(int newState)
{
db.Database.SqlCommand("UPDATE Table SET State = #p0", newState);
}
You'd call this from a client using a PUT /resources/state?newState=1.
It might be clearer to make newState an enum:
public enum State
{
New = 0,
Processed = 1,
Error = 2,
etc.
}
[HttpPut]
[Route("resources/state")]
public IHttpActionResult UpdateState(State newState)
{
db.Database.SqlCommand("UPDATE Table SET State = #p0", (int)newState);
}
Then your call becomes PUT /resources/state?newState=Processed which is a little clearer.
OData supports such kinds of operations. You can use OData Action to update the state.
Blog: odata-actions-and-functions
Sample: ODataActionSample
Following code converts the ViewModel query to model and then converts the returned result back to ViewModel as PageResult. All this works fine but when I try to use include as part of my default query(or even with the latest version as part of querycontext) then OData formatter plays funny and doesn't include child elements. I have debugged and confirmed that it actually contains child elements. This only happens for controllers that I extended from ODataController(so basically for the ones that are extended from ApiController all works fine but i need results in OData format).
Please note that I have also tried with the latest nightly build(Microsoft.Data.OData 5.5.0.0) and still it doesn't work for me.
Any help would highly be appreciated.
public class ProductsController : ODataController
{
APPContext context = new APPContext();
public PageResult<ProductViewModel> Get(ODataQueryOptions QueryOptions)
{
EdmModel model = new EdmModel();
ODataQueryContext queryContext = new ODataQueryContext(model.GetEdmModel(), typeof(Product));
var mappedQuery = new ODataQueryOptions(queryContext, QueryOptions.Request);
var results = new List<ProductViewModel>();
foreach (var result in mappedQuery.ApplyTo(this.context.Serials.Include("Status").Include("Category")))
{
AutoMapper.Mapper.CreateMap(result.GetType(), typeof(ProductViewModel));
results.Add(AutoMapper.Mapper.Map<ProductViewModel>(result));
}
PageResult<ProductViewModel> pr = new PageResult<ProductViewModel>(results.AsEnumerable<ProductViewModel>(), mappedQuery.Request.GetNextPageLink(), mappedQuery.Request.GetInlineCount());
return pr;
}
}
In OData related entities are represented as navigation links. So, if you have a customers feed, the related orders for each customer will not be part of the customers feed. Instead, they would be represented as navigation links. You can explicitly tell the OData service to expand the related entities using the $expand query option. So, if you want the related orders for each customer to be expanded, you should ask for the url ~/Customers?$expand=Orders.
Ok!
I have to say both technology are great. Although there seems that something I do not get it.
You have a data in you database (and let say you want to show data from a table that has references to other tables).
I have a model with List or IEnumerable or IQueryable or whatever...
So in my view I want do foreach through the list of object and take advantage of cool feature of references to other tables. No problem in controller while you are in
using (var datatabse = new MyEntity)
{
}
But when you get out of using db has disposed and you get common error The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.
So i do not see other options as creating in memory copies of entity objects...but you loose all cool EF4 references and you have to manually load data first in your model and then with foreach show it on the view.
So instead of List<(EF4Type)> or IEnumerable<(EF4Type)> or IQueryable<(EF4Type)>
you have to do List<(MyCustomHelperClass)> where MyCustomHelperClass represents a class with properties similiar to entity objects and probably some additional beacuse you do not have access to properties of referenced tables Then you have to do foreach and Load data into this List and the another #foreach on the view with Razor to show all.
Twice as much work and if project is big...you can see a bigger picture of how manny those helperClasses you need. Was all this cool new technology really meant to be used in that way?....or am I missing something.
You are probably getting that error when you reference a lazy loaded property in your view. You should eager load everything you need in the Controller before passing it to the View.
See Loading Related Objects (Entity Framework).
The following example will cause all courses to be retrieved with the departments in the same query. This is eager loading.
// Load all departments and related courses
var departments1 = context.Departments
.Include(d => d.Courses)
.ToList();
Without the Include() part, courses could be retrieved later (possibly after your context has been disposed in the view). This is called lazy loading.
Along with eager loading as remembered by jrummell, there's also another way of loading related entries, it's explicit loading. Let's suppose you have a User entity, with many Groups entities related to it. You can explicitly load them:
var user = context.Users.Find(id); // Load the user.
context.Entry(user)
.Collection(u => u.Groups)
.Load();
This way you don't have to use the .Include(), and you can even filter the Groups:
context.Entry(user)
.Collection(u => u.Groups)
.Query()
.Where(g => g.SomeProperty.Contains("something"))
.Load();
TheMentor,
Depending on whether you have a repository or a db context, this object should only live for the duration of the controller action (Request), so you should be able to do everything required within the confines of the action.
Maybe i've misunderstood, but based on your question, this is what your issue appears to be. If I have misunderstood, then I'd still suggest that the db repository or db context should be referenced across the controller, rather then invoking it inside the action each time.
so you should see something like this in your controller:
public class TasksController : BaseController
{
private readonly TaskService _serviceTasks;
public TasksController(IRepository repository)
{
_serviceTasks = new TaskService(repository);
}
//
// GET: /Tasks/
public ActionResult Index()
{
var viewModel = _serviceTasks.All<Task>();
return View(viewModel);
}
public ActionResult Details(int id)
{
var domainModel = _serviceTasks.GetById<Task>(id);
var viewModel = PopulateDetailsViewModel(domainModel);
return View(viewModel);
}
//.. rest of actions cut
}
I call an ajax enabled wcf service method ,
<script type="text/javascript">
function GetEmployee() {
Service.GetEmployeeData('1','5',onGetDataSuccess);
}
function onGetDataSuccess(result) {
Iteratejsondata(result)
}
</script>
and my method is ,
[OperationContract]
public string GetEmployeeData(int currentPage,int pageSize)
{
DataSet ds = GetEmployeeViewData(currentPage,pageSize);
return GetJSONString(ds.Tables[0]);
}
My Dataset ds contains three datatable but i am using the first one for my records...
Other two datatables have values how can i get them in result...
function onGetDataSuccess(result) {
Iteratejsondata(result)
}
Any suggestion...
The only suggestion: do not use DataSets over WCF!
DataSets are evil - they're huge, they carry lots of overhead, the mix data with behavior - all things you should try to avoid like the plague when doing proper SOA. This is doubly true when you're doing Ajax calls asynchronously - you want to transfer as little data as possible using JSON - and having a DataSet with DataTables does not help you at all for your JSON calls...
So really : get yourself acquainted with some kind of an ORM, and grab objects and lists of objects and toss the DataSets onto the digital recycling heap.....
For a small project, if you're using SQL Server as your backend, why not use Linq-to-SQL? Or if that doesn't work for you, check out Subsonic
I am trying to build an ADO.NET Data Service with lots of entities and a few service operations. On one side I created a ASP.NET Web Application, in which an ADO.NET Entity Data Model and an ADO.NET Data Service are located. On the other side I created a second ASP.NET Web Application that has a Service Reference to the Data Service.
Entities are coming through very well, I can use LINQ to retrieve the data I want:
TestEntities entities = new TestEntities(
new Uri("http://localhost/service/service.svc"));
var query = from customer in entities.Customers
where customer.ID == 1234
select customer;
query.ToList();
This works. However, retrieving information through Service Operations completely eludes me.
Data Service-side code:
public static void InitializeService(IDataServiceConfiguration config) {
config.SetEntitySetAccessRule("*", EntitySetRights.All);
config.SetServiceOperationAccessRule("*", ServiceOperationRights.All);
}
[WebInvoke]
public IQueryable<Customer> GetSomeCustomers() {
TestEntities entities = new TestEntities();
return from customer in entities.Customers
where customer.ID > 0 && customer.ID < 20
select customer;
}
When I added the Service reference to my client project, Visual Studio didn't pick up on any Service Operations. I know I can access them through constructed URIs and the BeginExecute method of either the DataServiceContext object or the TestEntities object (in this case), or something like that, but that is not how I want it.
What I want is to use LINQ to go through the returned data of the Service Operation.
Is this possible? It should be, right?
Simple stuff once you know.
Just a few things to know:
Currently DataServiceClientGenerator (which uses the EntityClassGenerator) doesnt create methods for the service operations.
Using CreateQuery method on the context is not supported for service operations, currently they work because there is no validation on the client side for that (you will notice that if you use CreateQuery the "()" is added to the end of the Query Method like this "http://localhost/service.svc/method()?parameter=2", you can use CreateQuery but it is not recommended.
Not all Service operations return values, but for this example i will only show an example for the ones that do.
public partial class NorthwindEntities
{
public IQueryable<Order> OrdersByRegion(int regionId)
{
return this.Execute<Orders>(new Uri(string.Format("{0}OrdersByCountry?regionId={1}", this.BaseUri, regionId), UriKind.RelativeOrAbsolute));
}
}
If you require more information please feel free to ask any questions.
PS.: On your example you dont need to create a new data context on your service operation (server side) the DataService has already a reference instantiated when the service is called.
You can actually override the create of the data context on the service side like this:
protected override NorthwindEntities CreateDataSource()
{
return new NorthwindEntities();
}