public APIController()
{
db = new ApplicationDbContext();
}
ApplicationDbContext db;
[HttpGet]
public List<Category> GetCategories()s
{
return db.Categories.ToList();
}
I am trying to get categories from the Web API. I am using AJAX, but it gives a 500 exception.
Since connection string is right and all setup correctly, There are 2 possible issues in the code I see:
1- Your Api Controller is named APIController which is a reserved word in .NET Api
2- Your get service is trying to return a complete Object from categories which might be related to parent objects and the parent objects are related to other related objects which results in returning the whole database.
I suggest using select new in lambda like this:
[HttpGet]
public List<Category> GetCategories()s
{
return db.Categories.Select(a => new { a.Name, a.ID, a.Description }).ToList();
}
This way you avoid querying the whole database.
Related
I have a WebAPI POST controller like the one below:
[ResponseType(typeof(Product))]
public async Task<IHttpActionResult> PostProduct(Product product)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
db.Products.Add(product);
await db.SaveChangesAsync();
return CreatedAtRoute("DefaultApi", new { id = product.Id }, product);
}
To be valid, it expects several values, lets say Name, Price, URL, ManufactureID, StatusID.
However, the POST will not always contain a value for StatusID for example, and therefore the above will fail, as i cannot be null.
But when the value is not sent by the POST, i want to 'intercept' and set the value in code. Let say to int 1.
How would i go about this?
I have been using DTOes for extraxting data from the API, in a nice and viewable way. Can DToes be used in POST also? If so, how? Or any other approach, to setting data, if it does not excist in the POST?
I would say create your Product request model which will be defined in your WebAPI models and there your can define your StatusID as a nullable. After your receive request you can map your Product request data to ProductDto and in that mapping you set your default values if you need them.
Altough you can intercept request on client side and update it but I'm not sure is that something that will work for you.
You should create a POST product class that is agnostic of the persistence. Don't use the generated Product class of your ORM. Using your example above, you should have a ProductModel class that will only contain the properties that the API client can update. Then do the mapping of the DTO to your product data model.
public async Task<IHttpActionResult> PostProduct(ProductModel model)
{
...
var product = db.Products.New();
//mapping here
product.Name = model.Name;
product.Price = model.Price;
}
In my edmx model are 2 related tables: Challenge and ChallengeNote (has FK back to ChallengeID)
I can do this in breeze all day long
var qry = dataservice.getQuery("Challenges");
However, this fails every time:
var qry = dataservice.getQuery("Challenges").expand("ChallengeNotes");
The searchFailed is called and is the only error information in the console.
return dataservice.execute(qry.inlineCount(true))
.then(seachSucceeded)
.fail(searchFailed);
Does Breeze support relational data like this?
Does one need to write some custom code to support?
What am I missing?
Here's related answered question, but I was already following (unless I missed something) the answer's solution (and why I have the 2 context.Configuration settings in my ContextProvider).
breezejs-error-when-loading-an-entity-with-related-data
Here's another similar question that's been unanswered breeze-expand-query-fails-with-object-object-has-no-method-getproperty
Here's my provider code (want to use the BeforeSaveEntity override further on in the project):
public class ModelProvider : EFContextProvider<ModelEntities>
{
public ModelProvider()
: base()
{
this.Context.Configuration.LazyLoadingEnabled = false;
this.Context.Configuration.ProxyCreationEnabled = false;
}
}
Here's my controller code:
[BreezeController]
public class DataController : ApiController
{
readonly ModelProvider _contextProvider = new ModelProvider();
[HttpGet]
public string Metadata()
{
return _contextProvider.Metadata();
}
[Queryable(AllowedQueryOptions = AllowedQueryOptions.All)]
[HttpGet]
public IQueryable<Challenge> Challenges()
{
return _contextProvider.Context.Challenges.Include(x => x.ChallengeNotes);
}
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
return _contextProvider.SaveChanges(saveBundle);
}
[HttpGet]
public IQueryable<ChallengeNote> ChallengeNotes()
{
return _contextProvider.Context.ChallengeNotes;
}
}
When I browse to the URL, it's including the related entity:
http://localhost:53644/breeze/data/Challenges?$filter=Active%20eq%20true&$top=10&$expand=ChallengeNotes&$inlinecount=allpages
Here is the data coming from the Controller
At this point all things, imo, are pointing to Breeze configuration on either the Server or Client.
TIA
Breeze absolutely does support this, but you do need to make sure that your Entity Framework model is set up correctly. Take a look at the DocCode sample in the Breeze zip for a number of examples of using both expand (client side) or EF include (server side) clauses.
One guess about your problem is that you are using the Breeze camelCasing naming convention and therefore your "expand" clause should be
var qry = dataservice.getQuery("Challenges").expand("challengeNotes");
i.e. "challengeNotes" (note the casing) is the name of the client side property that corresponds to a server side property of "ChallengeNotes". To clarify, "expand" clauses take the names of client side "properties" as parameters and property names are what are transformed as a result of the Breeze.NamingConvention.
In contrast, a query resource name i.e. "Challenges" in your example is the name of the server side resource ( as a result of marking your "Challenges" method with the [HttpGet] annotation. This name is NOT affected by the NamingConvention.
Side notes: Your example has both an expand and an Include clause. Either of these is sufficient all by itself. You do not need both. In general you can either include an "expand" clause in your client side query OR have an Entity Framework "Include" clause on the server. The advantage of the first is that you can control the expand on the client, the advantage of the second is that you can insure that every query for a specified resource always fetches some related entities.
Hope this helps!
I have a database CarsDB with a table Car with some columns (like mileage or model)
And I want to get info from that table in a controller I write:
public ActionResult Index()
{
return View(db.CarsDB.ToList()):
}
But I'm getting an error (something like method CarsDB not found). The error is long and I don't know hot to translate it to English :( Also, when I write db, the only suggetions I'm getting are "Equals", "GetHashCode" and some others, not with CarsDB
Try
db.Cars.ToList()
You need to query the table (cars) - right now you're saying "select everything from the CarsDB database", rather than "select everything from the Cars table in the CarsDB database".
To clarify - your db variable should be an instance of a data context or entities.
Full code should look something like this:
public ActionResult Index()
{
CarsDB db = new CarsDB();
return View(db.Cars.ToList()):
}
If you're using Entity Framework you could do something like:
public ActionResult Index()
{
using (CarsDB dataContext = new CarsDB())
{
return View(dataContext.Cars.ToList()):
}
}
This will also assure automatic disposal of your data context.
I understood how to communicate between Web, Worker role and the flow in MVC architecture.
My question is, after I query the data from a table in web role, how can the controller in MVC get this data to diplay in the view?
I tried using a global static variable in webrole, where the data gets populated, but when I access the static variable from the controller, it only returned 'null'. Why am I getting a null?
Thanks.
ok, in case you use the storage client, the implementation would be like:
Create your Model:
public class MyEntity : Microsoft.WindowsAzure.StorageClient.TableServiceEntity
{
public MyEntity()
{
PartitionKey = DateTime.UtcNow.ToString("MMddyyyy");
RowKey = string.Format("{0:10}_{1}",
DateTime.MaxValue.Ticks - DateTime.Now.Ticks, Guid.NewGuid());
}
// Define the properties.
public string Title { get; set; }
public string Name { get; set; }
}
}
2. Define your context class:
public class MyDataContext : TableServiceContext
{
public MyDataContext(string baseAddress,
StorageCredentials credentials)
: base(baseAddress, credentials)
{ }
public IQueryable GetMyEntity
{
get
{
return this.CreateQuery("MyTableName");
}
}
}
Implement your controller action method:
public ActionResult Index()
{
var context = new MyDataContext(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials);
var results = from g in context.GetMyEntity
where g.PartitionKey ==
DateTime.UtcNow.ToString("MMddyyyy")
select g;
return View(results.FirstOrDefault());
}
this is reference code only, which is very ugly and will hardly work as it is, but it still provides an example of how you can query the table storage in your MVC project.
are we talking about an application whose MVC part is hosted in a worker role and which gets data from a web role which is querying the table storage? Or are we talking about a ASP.NET MVC application here which is hosted in a web role?
static variables is not a good idea at all because of concurrency issues.
in case of scenario 1, how do you communicate with a web role? via web service call directly?
you cold simply call the service from your controller or delegate the call to another layer and then put this data in your model which is then displayed by the corresponding view.
have you tried debugging this application locally using the [azure local dev env][1]
[1]: http://blogs.msdn.com/b/morebits/archive/2010/12/01/using-windows-azure-development-environment-essentials.aspx ? or do you use the real azure infrastructure? Are you sure you are getting the data from your query? maybe the query is wrong? have you observed any exceptions?
we need more information here to be able to help you
I am very new to OData (only started on it yesterday) so please excuse me if this question is too dumb :-)
I have built a test project as a Proof of Concept for migrating our current web services to OData. For this test project, I am using Reflection Providers to expose POCO classes via OData. These POCO classes come from in-memory cache. Below is the code so far:
public class DataSource
{
public IQueryable<Category> CategoryList
{
get
{
List<Category> categoryList = GetCategoryListFromCache();
return categoryList.AsQueryable();
}
}
// below method is only required to allow navigation
// from Category to Product via OData urls
// eg: OData.svc/CategoryList(1)/ProductList(2) and so on
public IQueryable<Category> ProductList
{
get
{
return null;
}
}
}
[DataServiceKeyAttribute("CategoryId")]
public class Category
{
public int CategoryId { get; set; }
public string CategoryName { get; set; }
public List<Product> ProductList { get; set; }
}
[DataServiceKeyAttribute("ProductId")]
public class Product
{
public int ProductId { get; set; }
public string ProductName { get; set; }
}
To the best of my knowledge, OData is going to use LINQ behind the scenes to query these in-memory objects, ie: List in this case if somebody navigates to OData.svc/CategoryList(1)/ProductList(2) and so on.
Here is the problem though: In the real world scenario, I am looking at over 18 million records inside the cache representing over 24 different entities.
The current production web services make very good use of .NET Dictionary and Hashtable collections to ensure very fast look ups and to avoid a lot of looping. So to get to a Product having ProductID 2 under Category having CategoryID 1, the current web services just do 2 look ups, ie: first one to locate the Category and the second one to locate the Product inside the Category. Something like a btree.
I wanted to know how could I follow a similar architecture with OData where I could tell OData and LINQ to use Dictionary or Hashtables for locating records rather than looping over a Generic List?
Is it possible using Reflection Providers or I am left with no other choice but to write my custom provider for OData?
Thanks in advance.
You will need to process expression trees, so you will need at least partial IQueryable implementation over the underlying LINQ to Objects. For this you don't need a full blown custom provider though, just return you IQueryable from the propties on the context class.
In that IQueryable you would have to recognize filters on the "key" properties (.Where(p => p.ProductID = 2)) and translate that into a dictionary/hashtable lookup. Then you can use LINQ to objects to process the rest of the query.
But if the client issues a query with filter which doesn't touch the key property, it will end up doing a full scan. Although, your custom IQueryable could detect that and fail such query if you choose so.