I have the following Product class:
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
}
and the following Web API controller class:
public class ProductController : ApiController
{
public IQueryable<Product> Get()
{
var products = new List<Product>
{
new Product {Id = 1, Name = "Beans"},
new Product {Id = 2, Name = "Sausages"},
new Product {Id = 3, Name = "Bread"}
};
return products.AsQueryable();
}
}
I am using Fiddler to make requests to it. These work just fine:
localhost:49629/API/Product
localhost:49629/API/Product?$orderby=Name
But when I try to use filtering, such as:
localhost:49629/API/Product?$filter=Id gt 2
a null reference occurs. There is no source code available in the debugger, so I am unsure what has gone wrong. Can anyone help?
For Fiddler you need to encode the request:
localhost:49629/API/Product?$filter=Id%20gt%202
Related
Hi i have a C# model class. This class i need to pass as json response by setting his property . one property name Product of this class have type of another product class, when there is no data for Product i am getting all inner property value as blank but instead of that i want blank json property .
For Exp My Class is
public class Profile_BO
{
public int Id { get; set; }
public string Username { get; set; }
public Product product{ get; set; }
public class Product
{
public int Id { get; set; }
public string Type { get; set; }
}
}
i am initializing this class from C# data table like below : -
Profile_BO profile_BO = new Profile_BO();
foreach (DataRow dr in result.Tables[0].Rows)
{
profile_BO.Id = Convert.ToInt32(dr[0]);
profile_BO.Username = Convert.ToString(dr[1]);
}
Product product = new Product();
foreach (DataRow dr1 in result.Tables[1].Rows)
{
product.Id = Convert.ToInt32(dr1[0]);
product.Type = Convert.ToString(dr1[1]);
}
profile_BO.product = product;
Finally when i am passing as a response to method : -
public async Task<HttpResponseMessage> GetUserInfo(Profile_Request profile_Request)
{
return request.CreateResponse(HttpStatusCode.OK, profile_BO);
}
And when calling on client side i am getting response json if data is present in table like : -
{
"Id": "1",
"Username": "abc",
"product": {
"Id": "232",
"Type": "34cvdcbv"
}
}
But when i have no data in product table i am getting below : -
{
"Id": "1",
"Username": "abc",
"product": {
"Id": 0,
"Type": ""
}
}
But if no data i want output like below : -
{
"Id": "1",
"Username": "abc",
"product": {}
}
One other question is : - Is it right way for binding response model from dataset ?
the problem you are facing, is that you are initializing an instance of Product regardless of the fact, that there might be no product at all. this results, to its properties getting initialized with default values. Int32 defaults to 0. System.String as a reference type is null.
Profile_BO profile_BO = new Profile_BO();
foreach (DataRow dr in result.Tables[0].Rows)
{
profile_BO.Id = Convert.ToInt32(dr[0]);
profile_BO.Username = Convert.ToString(dr[1]);
}
//I am assuming you only expect one row, since oyur model uses a single Product
//and no collection of products. No need for a loop then.
if(result.Tables[1].Rows.Count == 1) {
Product product = new Product();
var dr1 = result.Tables[1].Rows[0];
product.Id = Convert.ToInt32(dr1[0]);
product.Type = Convert.ToString(dr1[1]);
profile_BO.product = product;
}
This should result in the following JSON being returned:
{
"Id": "1",
"Username": "abc",
"product": null
}
EDIT: If you really must have product : {}, then you need ot change your model.
public class Profile_BO
{
public int Id { get; set; }
public string Username { get; set; }
public object product { get; set; }
}
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
}
Declare product as an object. Since all classes inherit from object, you can instantiate it as an object or Product, depending on your case:
if(result.Tables[1].Rows.Count == 1) {
Product product = new Product();
var dr1 = result.Tables[1].Rows[0];
product.Id = Convert.ToInt32(dr1[0]);
product.Type = Convert.ToString(dr1[1]);
profile_BO.product = product;
}
Or:
if(result.Tables[1].Rows.Count == 0) {
var product = new object();
profile_BO.product = product;
}
This will then result in:
{"Id":1,"Username":"Foo Bar","product":{}}
However I strongly advise to go with the first approach, because this will make testing and modifications easier, since you keep your strongly typed approach.
My previous answer doesn't contribute to your final question. So here is my edited solution.
A Better Solution
May be better solution is using Custom Message Handler.
A delegating handler can also skip the inner handler and directly
create the response.
Custom Message Handler:
public class NullJsonHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var updatedResponse = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = null
};
var response = await base.SendAsync(request, cancellationToken);
if (response.Content == null)
{
response.Content = new StringContent("{}");
}
else if (response.Content is ObjectContent)
{
var contents = await response.Content.ReadAsStringAsync();
if (contents.Contains("null"))
{
contents = contents.Replace("null", "{}");
}
updatedResponse.Content = new StringContent(contents,Encoding.UTF8,"application/json");
}
var tsc = new TaskCompletionSource<HttpResponseMessage>();
tsc.SetResult(updatedResponse);
return await tsc.Task;
}
}
Register the Handler:
In Global.asax file inside Application_Start() method register your Handler by adding below code.
GlobalConfiguration.Configuration.MessageHandlers.Add(new NullJsonHandler());
Now all the Asp.NET Web API Response which contains null will be replaced with empty Json body {}.
References:
1.
2.
I'm trying to allow my entities to be ordered by the Last-Modified property in their metadata, using OData query options.
I tried using a transformer as described in Converting to JSON and accessing metadata, but when I apply ODataQueryOptions to the resulting IQueryable, I get an empty array.
The model and view-model:
public class Foo
{
public int Id { get; set; }
}
public class FooViewModel
{
public string Id { get; set; }
public DateTime LastModified { get; set; }
}
The transformer:
public class Foos_WithLastModified : AbstractTransformerCreationTask<Foo>
{
public Foos_WithLastModified()
{
TransformResults = foos => from foo in foos
let metadata = MetadataFor(foo)
select new
{
Id = foo.Id.ToString(CultureInfo.InvariantCulture),
LastModified = metadata.Value<DateTime>("Last-Modified")
};
}
}
The relevant method in FooController (_session is an IAsyncDocumentSession):
public async Task<ICollection<FooViewModel>> Get(ODataQueryOptions<FooViewModel> options)
{
var settings = new ODataValidationSettings();
settings.AllowedOrderByProperties.Add("LastModified");
options.Validate(settings);
var foos = _session.Query<Foo>()
.TransformWith<Foos_WithLastModified, FooViewModel>();
var odataFoos = (IQueryable<FooViewModel>)options.ApplyTo(foos);
return await odataFoos.ToListAsync();
}
When I hit /api/Foo, the results are as expected:
[
{
"Id": "foos/456",
"LastModified": "2015-11-23T08:43:10.913662Z"
},
{
"Id": "foos/123",
"LastModified": "2015-11-23T08:50:34.0907996Z"
}
]
But when I add OData query options (/api/Foo?$orderby=LastModified), I get an empty array: [].
I also tried changing _session to an IDocumentSession and modifying Get as follows,
[EnableQuery(AllowedOrderByProperties = "LastModified")]
public IQueryable<FooViewModel> Get()
{
return _session.Query<Foo>()
.TransformWith<Foos_WithLastModified, FooViewModel>();
}
but I get the same results.
Are transformers the wrong approach? How can I sort by Last-Modified using OData query options?
I do not know how to handle the OData stuff, never tried that, but in order to query for entities, ordered by the metadata value "Last-Modified" using only RavenDB techniques you can do the following:
Create an index for your entity (in my example a Customer). In this index we add the field LastModified that's using the document's metadata value for Last-Modified.
public class Customer_ByLastModified : AbstractIndexCreationTask<Customer>
{
public class QueryModel
{
public DateTime LastModified { get; set; }
}
public Customer_ByLastModified()
{
Map = customers => from customer in customers
select new
{
LastModified = this.MetadataFor(customer).Value<DateTime>("Last-Modified")
};
}
}
The QueryModel isn't mandatory, but it makes querying via the client API easier, imo. You can then add a Transformer to be able to use the metadata value in your return model:
public class Customers_WithLastModified : AbstractTransformerCreationTask<Customer>
{
public Customers_WithLastModified()
{
TransformResults = results => from customer in results
select new CustomerViewModel
{
Id = customer.Id,
Name = customer.Name,
LastModified = MetadataFor(customer).Value<DateTime>("Last-Modified")
};
}
}
And then query it like this:
using (var session = documentStore.OpenSession())
{
var customers = session.Query<Customer_ByLastModified.QueryModel, Customer_ByLastModified>()
.OrderByDescending(x => x.LastModified)
.TransformWith<Customers_WithLastModified, CustomerViewModel>()
.ToList();
}
Hope this helps!
I'm new in Entity Framework and I'm testing a simple application but it doesn't work.
Let me explain step by setp what I'm doing:
1- Create a Console App using VS 2013 Express
2- Include a reference to EF6 by Nuget
3- Create the Student Class:
namespace CSharp_CodeFirst
{
public class Student
{
public int Id { get; set; }
public string name { get; set; }
public string email { get; set; }
}
}
4- Create the context class
using System.Data.Entity;
namespace CSharp_CodeFirst
{
public class StudentDataContext : DbContext
{
public StudentDataContext() : base()
{
}
public DbSet<Student> Students;
}
}
5- Create the code in Program.cs
namespace CSharp_CodeFirst
{
class Program
{
static void Main(string[] args)
{
using (var ctx = new StudentDataContext())
{
Student stud = new Student() { name = "New Student", email="test#test.com" , Id=1 };
ctx.Students.Add(stud);
ctx.SaveChanges();
}
}
}
}
6- Build without errors
7- When I execute the project I get the error :
An unhandled exception of type 'System.NullReferenceException' occurred in CSharp_CodeFirst.exe
Object reference not set to an instance of an object.
The error occur in this line of code : ctx.Students.Add(stud);
I'm using the sample in this site : http://www.entityframeworktutorial.net/code-first/simple-code-first-example.aspx
I Feel Like I'm Forgetting Something, but What ???
Thanks
I just followed an MVC tutorial on creating an image Gallery, which connects the Controller to the data connection, like this:
ImageController.cs:
...
private CustomMembershipDB db = new CustomMembershipDB();
public ViewResult Index()
{
return View(db.lm_pics.ToList());
}
...
Instead of connecting directly to CustomMembershipDB, I'd like to use my own Model named GalleryModel.cs. I'm thinking this would allow me to create more functionality that just direct data access.
I am not sure how to write this model, or how to reference it in the controller so that it behaves the same way as a direct database connection does now.
Currently, my GalleryModel.cs file looks lke this (edited to correct error):
namespace LMProj_MVC.Models
{
public class GalleryModel
{
public string Picname { get; set; }
public string Decription{ get; set; }
public int Userid { get; set; }
}
public class PicDBContext : CustomMembershipDB
{
public DbSet<GalleryModel> GalleryModel { get; set; }
}
}
I'd like to be able to show the gallery using an iEnumberable list as I am doing now, in addition to creating other methods. Could someone tell me what I'm missing?
You need to create an instance of your model object for each of your database pictures. You could use LINQ to do this, for example:
var picSummaries = db.lm_pics.Select(pic => new GalleryModel{
Picname = pic.Name,
Description = pic.Description,
Userid = pic.User.Id
});
Or you could use a for each loop:
var picSummaries = new List<GalleryModel>();
foreach (var pic in db.lm_pics)
{
picSummaries.Add(new GalleryModel{
Picname = pic.Name,
Description = pic.Description,
Userid = pic.User.Id
});
}
then return the view as before:
return View(picSummaries);
Perhaps there is an easy solution for my problem but I simply cannot seem to find it. I have read lots of tutorials about Knockout so I get the basics but I ask this question because my entity-structure is a bit more complicated than a person with a name and a list of friends which may or may not be on Twitter (Video on Channel9: Helping you build dynamic JavaScript UIs with MVVM and ASP.NET). Here's my situation:
I have a class PersonnelClass with this basic structure:
[Serializable]
//The interface is for the implementation of 'Name' and 'Description'
public class PersonnelClass : IPersonnelClassOrPerson
{
public PersonnelClass() : this(Guid.NewGuid(), "", "") { }
public PersonnelClass(Guid id, String name, String description = null)
{
if (id == Guid.Empty) { throw new ArgumentNullException("id"); }
Id = id;
Name = name;
Description = description;
Properties = new PropertyCollection();
}
public Guid Id { get; private set; }
public String Name { get; set; }
public String Description { get; set; }
public PropertyCollection Properties { get; private set; }
}
The PropertyCollection class and associated AbstractProperty class look like this:
[Serializable]
public class PropertyCollection: List<AbstractProperty> { }
[Serializable]
public abstract class AbstractProperty: IEntity, IProperty
{
public AbstractProperty(String name, String description = null) : this(Guid.NewGuid(), name, description) { }
public AbstractProperty(Guid id, String name, String description = null)
{
if (id == Guid.Empty) { throw new ArgumentNullException("id"); }
if (String.IsNullOrEmpty(name)) { throw new ArgumentNullException("name"); }
Id = id;
Name = name;
Description = description;
}
public Guid Id { get; private set; }
public String Name { get; private set; }
public String Description { get; private set; }
}
In my Controller, I create an instance of a PersonnelClassViewModel that has this structure:
public class PersonnelClassViewModel
{
public PersonnelClass PersonnelClass { get; set; }
public List<AbstractProperty> Properties { get; set; }
}
I fill this viewmodel with a new PersonnelClass and two test-properties to pass to my View like this:
var properties = new List<AbstractProperty>
{
new TextProperty("prop1", "descr1"),
new TextProperty("prop2", "descr2")
//TextProperty is derived from AbstractProperty
};
var vm = new PersonnelClassViewModel { Properties = properties };
return View(vm);
I get everything in my View as I wanted. From the View I want to create a new PersonnelClass with a set of selected properties. I have the fields for Name and Description and to add the properties I have a ListBox with the properties that already exist (for demo-purpose they came from the controller now). Through a bit of Knockout JavaScript code I can select items from this list and populate an HTML select-control () with the selected properties to add to the PersonnelClass. This all works fine, until I want to build up an object to pass back to the Controller and create the PersonnelClass.
My question is: what Knockout JS code is needed to build up this object and pass it to the Controller by submitting the form and in my Controller how should I receive this object, meaning: what type of object should this be (PersonnelClass, PersonnelClassViewModel, ...) ?
If any more info/code is needed, please do ask. Thanks in advance!
Update after answer of 'B Z':
I followed a few more of Steven Sanderson's tutorials about this to be sure I understand this, especially the one you provided in your answer. Now I have following code in my View to start with:
var initialData = #Html.Raw(new JavaScriptSerializer().Serialize(Model));
var viewModel = {
personnelClassViewModel : ko.mapping.fromJS(initialData),
properties : personnelClassViewModel.Properties,
selectedProperties : ko.observableArray([]),
addedProperties : ko.observableArray([])
};
ko.applyBindings(viewModel);
The variable 'initialData' contains the values I expect it to have but then I get the following error:
Microsoft JScript runtime error: 'personnelClassViewModel' is undefined
I have no clue anymore. Can anyone help me fix this?
Steven Sanderson has an example of how to to work with variable length lists and knockoutjs
http://blog.stevensanderson.com/2010/07/12/editing-a-variable-length-list-knockout-style/
Having said that, I think your problem isn't so much on the knockout side and more on the how to databind the data correctly on the server side. In the link above, Steven uses a FromJson attribute to model bind which you may find useful...
HTH