I'm developing small app to pratice and I'm having a problem understanding why the object I pass is Null.
I have a main ViewModelPage where I have a Button:
[RelayCommand]
private async Task CellDoubleTapped()
{
Patient patient = new Patient(Id, Date);
var navigationParameter = new Dictionary<string, object>
{
{ "obj", patient }
};
await Shell.Current.GoToAsync($"//{nameof(EditingPage)}", navigationParameter);
}
With this button I wanted to open a new page "EditingPage", where I pass my patient object, and there I present the user with fields to edit.
My EditingViewModel:
[QueryProperty(nameof(obj), "obj")]
public partial class EditingViewModel: BaseViewModel
{
public Patient obj { get; set; }
public string Date { get; set; }
public EditingViewModel()
{
ShowFields();
}
private void ShowFields()
{
Date = obj.Date;
}
}
I recieve an Exception stating my obj is NULL. "object reference not set to an instance of an object"
Can you help me understand which concepts I'm not understanding.
I expected to access the object I created in a page in another page. I'm trying to pass it through Navigation like presented in the documentation from Microsoft. Maybe my error is not about that but there's a concept about passing classes I'm consfusing
I am playing around with Blazor right now. And I found a strange behaviour and I am not quite sure, if it's my, Azure's or Blazor's (it's still experimental, so it's possible) fault. My project is ASP.NET core hosted (on Azure, but I already told that).
I've got the following model:
namespace MyProject.Shared
{
public class Emoji
{
public List<string> UnicodeCharacters { get; set; }
public string Description { get; set; }
public Emoji()
{
UnicodeCharacters = new List<string>();
}
}
}
The following controller:
namespace MyProject.Server.Controllers
{
[Route("api/[controller]")]
public class EmojiPickerController : Controller
{
[HttpGet("[action]")]
public IEnumerable<Emoji> GetEmojis()
{
var emojis = new List<Emoji>();
var emoji = new Emoji();
emoji.Description = "Foo";
emoji.UnicodeCharacters.Add("Bar");
return emojis;
}
}
}
And finally my component:
namespace MyProject.Client.Classes
{
public class EmojiPicker : BlazorComponent
{
[Inject]
protected HttpClient Http { get; set; }
public List<Emoji> Emojis = new List<Emoji>();
protected override async Task OnInitAsync()
{
var emojiArray = await Http.GetJsonAsync<Emoji[]>("api/EmojiPicker/GetEmojis");
Emojis = emojiArray.ToList<Emoji>();
}
}
}
Everything works just fine when I launch it locally. I've got the object in my view and can do stuff with it (e.g. printing "foo" and "bar" on the screen ;)).
But it's not like that on my Azure WebApp. It just doesn't work:
The WeatherCast sample works btw on both platforms. Any ideas?
Okay, after restarting my Azure application everything works just fine. Weird.
I am working with ASP.NET MVC 5 Web Api. I want consult all my users.
I wrote api/users and I receive this:
"The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'"
In WebApiConfig, already I added these lines:
HttpConfiguration config = new HttpConfiguration();
config.Formatters.XmlFormatter.SupportedMediaTypes.Remove(appXmlType);
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
But it still doesn't work.
My function for return data is this:
public IEnumerable<User> GetAll()
{
using (Database db = new Database())
{
return db.Users.ToList();
}
}
If you are working with EF, besides adding the code below on Global.asax
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
GlobalConfiguration.Configuration.Formatters
.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
Dont`t forget to import
using System.Data.Entity;
Then you can return your own EF Models
Simple as that!
When it comes to returning data back to the consumer from Web Api (or any other web service for that matter), I highly recommend not passing back entities that come from a database. It is much more reliable and maintainable to use Models in which you have control of what the data looks like and not the database. That way you don't have to mess around with the formatters so much in the WebApiConfig. You can just create a UserModel that has child Models as properties and get rid of the reference loops in the return objects. That makes the serializer much happier.
Also, it isn't necessary to remove formatters or supported media types typically if you are just specifying the "Accepts" header in the request. Playing around with that stuff can sometimes make things more confusing.
Example:
public class UserModel {
public string Name {get;set;}
public string Age {get;set;}
// Other properties here that do not reference another UserModel class.
}
Given right answer is one way to go, however it is an overkill when you can fix it by one config settings.
Better to use it in the dbcontext constructor
public DbContext() // dbcontext constructor
: base("name=ConnectionStringNameFromWebConfig")
{
this.Configuration.LazyLoadingEnabled = false;
this.Configuration.ProxyCreationEnabled = false;
}
Asp.Net Web API Error: The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'
Add this code to global.asax below on Application_Start:
Update from .Ignore to .Serialize . It must work.
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Serialize;
GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
public class UserController : ApiController
{
Database db = new Database();
// construction
public UserController()
{
// Add the following code
// problem will be solved
db.Configuration.ProxyCreationEnabled = false;
}
public IEnumerable<User> GetAll()
{
return db.Users.ToList();
}
}
I resolved it using this code to WebApiConfig.cs file
var json = config.Formatters.JsonFormatter;
json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
config.Formatters.Remove(config.Formatters.XmlFormatter);
I don't like this code:
foreach(var user in db.Users)
As an alternative, one might do something like this, which worked for me:
var listOfUsers = db.Users.Select(r => new UserModel
{
userModel.FirstName = r.FirstName;
userModel.LastName = r.LastName;
});
return listOfUsers.ToList();
However, I ended up using Lucas Roselli's solution.
Update: Simplified by returning an anonymous object:
var listOfUsers = db.Users.Select(r => new
{
FirstName = r.FirstName;
LastName = r.LastName;
});
return listOfUsers.ToList();
Adding this in your Application_Start() method of Global.asax file should solve the problem
protected void Application_Start()
{
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
GlobalConfiguration.Configuration.Formatters
.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
// ...
}
METHOD 2: [Not recommended]
If you are working with EntityFramework, you can disable proxy in your DbContext class constructor. NOTE: this code wll be removed if you update the model
public class MyDbContext : DbContext
{
public MyDbContext()
{
this.Configuration.ProxyCreationEnabled = false;
}
}
There's also this scenario that generate same error:
In case of the return being a List<dynamic> to web api method
Example:
public HttpResponseMessage Get()
{
var item = new List<dynamic> { new TestClass { Name = "Ale", Age = 30 } };
return Request.CreateResponse(HttpStatusCode.OK, item);
}
public class TestClass
{
public string Name { get; set; }
public int Age { get; set; }
}
So, for this scenario use the [KnownTypeAttribute] in the return class (all of them) like this:
[KnownTypeAttribute(typeof(TestClass))]
public class TestClass
{
public string Name { get; set; }
public int Age { get; set; }
}
This works for me!
My personal favorite: Just add the code below to App_Start/WebApiConfig.cs. This will return json instead of XML by default and also prevent the error you had. No need to edit Global.asax to remove XmlFormatter etc.
The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8
config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
Just put following lines in global.asax:
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
Import
using System.Data.Entity;
Use AutoMapper...
public IEnumerable<User> GetAll()
{
using (Database db = new Database())
{
var users = AutoMapper.Mapper.DynamicMap<List<User>>(db.Users);
return users;
}
}
Use the following namespace:
using System.Web.OData;
Instead of :
using System.Web.Http.OData;
It worked for me
Add the below line
this.Configuration.ProxyCreationEnabled = false;
Two way to use ProxyCreationEnabled as false.
Add it inside of DBContext Constructor
public ProductEntities() : base("name=ProductEntities")
{
this.Configuration.ProxyCreationEnabled = false;
}
OR
Add the line inside of Get method
public IEnumerable<Brand_Details> Get()
{
using (ProductEntities obj = new ProductEntities())
{
this.Configuration.ProxyCreationEnabled = false;
return obj.Brand_Details.ToList();
}
}
Use [Serializable] for class:
Example:
[Serializable]
public class UserModel {
public string Name {get;set;}
public string Age {get;set;}
}
It worked for me!
Solution that worked for me:
Use [DataContract] for class and [DataMember] attributes for each property to serialize. This is enough to get Json result (for ex. from fiddler).
To get xml serialization write in Global.asax this code:
var xml = GlobalConfiguration.Configuration.Formatters.XmlFormatter;
xml.UseXmlSerializer = true;
Read this article, it helped me to understand serialization:
https://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization
To add to jensendp's answer:
I would pass the entity to a user created model and use the values from that entity to set the values in your newly created model. For example:
public class UserInformation {
public string Name { get; set; }
public int Age { get; set; }
public UserInformation(UserEntity user) {
this.Name = user.name;
this.Age = user.age;
}
}
Then change your return type to: IEnumerable<UserInformation>
While all these answers above are correct, one may want to check the InnerException > ExceptionMessage.
If it says something like this "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.". This could be an issue because of default behavior of the EF.
By assigning LazyLoadingEnabled = false in your DbContext constructor will do the trick.
public class MyDbContext : DbContext
{
public MyDbContext()
{
this.Configuration.LazyLoadingEnabled = false;
}
}
For more detailed reading about EagerLoading and LazyLoading behavior of EF refer this MSDN Article.
In my case I have had similar error message:
The 'ObjectContent`1' type failed to serialize the response body for
content type 'application/xml; charset=utf-8'.
But when I dig deeper in it, the issue was:
Type 'name.SomeSubRootType'
with data contract name
'SomeSubRootType://schemas.datacontract.org/2004/07/WhatEverService'
is not expected. Consider using a DataContractResolver if you are
using DataContractSerializer or add any types not known statically to
the list of known types - for example, by using the KnownTypeAttribute
attribute or by adding them to the list of known types passed to the
serializer.
The way I solved by adding KnownType.
[KnownType(typeof(SomeSubRootType))]
public partial class SomeRootStructureType
This was solved inspired from this answer.
Reference: https://msdn.microsoft.com/en-us/library/ms730167(v=vs.100).aspx
I basically add one line which they are
entities.Configuration.ProxyCreationEnabled = false;
to UsersController.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using UserDataAccess;
namespace SBPMS.Controllers
{
public class UsersController : ApiController
{
public IEnumerable<User> Get() {
using (SBPMSystemEntities entities = new SBPMSystemEntities()) {
entities.Configuration.ProxyCreationEnabled = false;
return entities.Users.ToList();
}
}
public User Get(int id) {
using (SBPMSystemEntities entities = new SBPMSystemEntities()) {
entities.Configuration.ProxyCreationEnabled = false;
return entities.Users.FirstOrDefault(e => e.user_ID == id);
}
}
}
}
You will have to define Serializer Formatter within WebApiConfig.cs available in App_Start Folder like
Adding config.Formatters.Remove(config.Formatters.XmlFormatter);
// which will provide you data in JSON Format
Adding config.Formatters.Remove(config.Formatters.JsonFormatter);
// which will provide you data in XML Format
Another case where I received this error was when my database query returned a null value but my user/view model type was set as non-nullable. For example, changing my UserModel field from int to int? resolved.
This also happens when the Response-Type is not public!
I returned an internal class as I used Visual Studio to generate me the type.
internal class --> public class
Visual Studio 2017 or 2019 is totally unthoughtful on this, because Visual Studio itself requires the output to be in json format, while Visual Studio's default format is "XmlFormat" (config.Formatters.XmlFormatter).
Visual Studio should do this automatically instead of giving developers so much trouble.
To correct this problem, go to the WebApiConfig.cs file, and add
var json = config.Formatters.JsonFormatter;
json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
config.Formatters.Remove(config.Formatters.XmlFormatter);
after "config.MapHttpAttributeRoutes();" in the Register(HttpConfiguration config) method. This would allow your project to produce json output.
In my case I solved recreating the database.
I made some changes in a model and launching Update-Database in Package Manager Console I got the following Error:
"The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Activities_dbo.Projects_ProjectId". The conflict occurred in database "TrackEmAllContext-20190530144302", table "dbo.Projects", column 'Id'."
In case: If adding code to WebApiConfig.cs or Global.asax.cs doesn't work for you:
.ToList();
Add .ToList() function.
I tried out every solution but following worked for me:
var allShops = context.shops.Where(s => s.city_id == id)**.ToList()**;
return allShops;
I hope, it helps.
in my case, it was fixed when I removed the virtual keyword before my navigation properties,
I mean the reference tables.
so I changed
public virtual MembershipType MembershipType { get; set; }
to:
public MembershipType MembershipType { get; set; }
I'm working on a website, where I need to retrieve pricelists, from another database on the same SQL Server as my Umbraco database.
It's a requirement that it has to be in a separate database.
I have made a new connection string Pricelist and used EF database-first.
PriceList repository:
namespace UmbracoCMS.Repository{
using System;
using System.Collections.Generic;
public partial class Prisliste
{
public string Kode { get; set; }
public string Speciale { get; set; }
public string Ydelsesgruppe { get; set; }
public string Gruppe { get; set; }
public string Ydelse { get; set; }
public string Ydelsestekst { get; set; }
public string Anaestesi { get; set; }
public string Indlæggelse { get; set; }
public Nullable<double> Listepris { get; set; }
public Nullable<int> WebSort { get; set; }
public string YdelsesTekstDK { get; set; }
public string Frapris { get; set; }
public Nullable<int> Sortering { get; set; }
}
}
PriceListController class:
using System;
using System.Linq;
using System.Web.Mvc;
using UmbracoCMS.Repository;
namespace UmbracoCMS.Controllers{
public class PriceListController : Umbraco.Web.Mvc.SurfaceController {
[HttpGet]
public PartialViewResult GetPriceList(string contentTitle){
var db = new PricelistContext();
var query = from b in db.Prislistes orderby b.Speciale select b;
Console.WriteLine("records in the database:");
foreach (var item in query)
{
Console.WriteLine(item.Speciale);
}
return PartialView("~/views/partials/PriceList.cshtml");
}
}
}
What I want is to load the prices for a treatment, based on a property on the document type. I'm just not sure how do this in umbraco since I'm fairly new a umbraco.
So when a treatment page is requested, I need to take the property ContentTitle value. Use it to retrieve all records with the same Speciale and display them in a list/table.
With a query
.where(b.Speciale = contentTitle)
It would be great if someone could help a little, or lead me in the right direction.
Also is it possible to do it in the same http request? Or should I use partial view or macros to both get the properties of the document type, from the umbraco database, and the records from the pricelist database at the same time when a user go to the treatment page?
Or is there a better way to do this?
Update:
Thanks a lot, for the great answer Ryios.
I got a question more.
using System;
using System.Linq;
using System.Web.Mvc;
namespace UmbracoCMS.Controllers
{
public class PriceListSurfaceController : Umbraco.Web.Mvc.SurfaceController
{
public ActionResult GetPriceList(string contentTitle)
{
PricelistContext.RunInContext(db =>
{
var result = db.Prislistes.OrderBy(p => p.Speciale);
});
return View(result);
}
}
}
I got it working, so it call the method and the data from the Pricelist Database is shown in:
var result = db.Prislistes.OrderBy(p => p.Speciale);
Now I just need to get the list of prices out to the view again, so I can show a list or table of the prices.
Do you have a suggestion on how I can this in Umbraco. Normally I would return a ViewModel in MVC like:
return View(new ListViewModel(result));
and use it in the view like:
#model Project.ViewModels.ListViewModel
So I can loop through it.
But I want to still have the properties from the the "Home"/"TreatmentPage" Document type.
Should I do it with a partialView or is there a better way?
Solved
I thought I wanted to share it, if anyone else is in a similar situaction.
Controller:
namespace UmbracoCMS.Controllers
{
public class PriceListSurfaceController : Umbraco.Web.Mvc.SurfaceController
{
public PartialViewResult PriceList(string contentTitle)
{
List<Prisliste> result = null;
PricelistContext.RunInContext(db =>
{
result = db.Prislistes.Where(p => p.Speciale == contentTitle)
.OrderBy(p => p.Speciale).ToList();
});
var model = result.Select( pl => new PrislistVm()
{
Speciale = pl.Speciale,
Listepris= pl.Listepris
});
return PartialView(model);
}
}
}
ViewModel:
namespace UmbracoCMS.ViewModels
{
public class PrislistVm
{
public PrislistVm()
{
Results = new List<Prisliste>();
}
public List<Prisliste> Results { get; set; }
public string Speciale { get; set; }
public double listepris { get; set; }
}
}
View/PriceListSurface:
#model IEnumerable<UmbracoCMS.ViewModels.PrislistVm>
#{
ViewBag.Title = "PriceList";
}
<h2>PriceList</h2>
#foreach (var item in Model)
{
#item.Speciale
#item.Listepris
}
Your going to have a memory leak if you load your EF context like that. I recommend creating a method to wrap it for you with a llambda callback. Put it in your context class.
public static void RunInContext(Action<PricelistContext> contextCallBack)
{
PricelistContext dbContext = null;
try
{
dbContext = new PricelistContext();
contextCallBack(dbContext);
}
finally
{
dbContext.Dispose();
dbContext = null;
}
}
//Example Call
PricelistContext.RunInContext(db => {
var result = db.PrisListes.OrderBy(p => p.Speciale);
//loop through your items
});
To get the Value of the DocumentType, it depends on the calling context. Assuming you are using a Razor Template that is attached to the document type, that is associated with a Content Page.
#inherits Umbraco.Web.Mvc.UmbracoTemplatePage
#{
Layout = "ContentPageLayout.cshtml";
}
#* Call GetPriceList on PriceListController with Parameter contentTitle *#
#Html.Action("GetPriceList", "PriceListSurface", new { contentTitle = Model.Content.GetPropertyValue<string>("ContentTitle") });
In the above example, I have created a document type with a property called ContentTitle that is associated with a view called ContentPage. Then I created content in the backoffice Content section called "Home" that uses the document type. Giving me a url like
http://localhost/home
Also, your SurfaceController will not work. Umbraco's logic for mapping the routes for surface controllers has some requirements for your surface controller's naming conventions. You have to end the name of the class with "SurfaceController" and then it get's called PriceListSurfaceController, then it maps the controller with a name of "PriceListSurface".
Here's the documentation for the SurfaceController features.
http://our.umbraco.org/documentation/Reference/Mvc/surface-controllers
Using a surface controller is the right logic. It's not good practice to have your Data Layer code calls in the UmbracoTemplatePage. 1, because RazorTemplates are interpreted/compiled and SurfaceController's are JIT compiled int the dll, so SurfaceController code is WAY faster. 2 Because you can make asynchronous Controller calls in MVC Razor. If it was all in the view it would make it really difficult to convert everything to be asynchronous. It's best to keep server side logic in a controller.
Optionally, you can Hijack an Umbraco route and replace it with a custom controller that doesn't have to inherit from SurfaceController, which makes it possibly to surface content to the browser that is or isn't part of umbraco.
http://our.umbraco.org/documentation/Reference/Mvc/custom-controllers
You can also create a new section in the backoffice to manage your Price List "the ui framework for building one is written against AngularJS"
http://www.enkelmedia.se/blogg/2013/11/22/creating-custom-sections-in-umbraco-7-part-1.aspx
I have the following error when I try to query my MVC 4 WebApi service
Extra content at the end of the document
Below is a rendering of the page up to the first error.
55Author Namehttp://images.myserver.com/authorspictures/nophoto.jpg
I looked into the Author class generated by Linq To Sql and found out that the next property of the Author object just after the image URL is this one:
[Association(Name = "Author_Quote", Storage = "_Quotes", ThisKey = "Id", OtherKey = "AuthorId")]
public EntitySet<Quote> Quotes { get; set; }
My undertanding is that there is some problem when generating the XML for this property causing the above error. However I don't know how I can prevent that and make it working correctly. Most examples I found regarding webApi were using POCO lists so they can't help me on this matter.
Any advices?
Below is my code
public class AuthorController : ApiController
{
IAuthorRepository repository;
public AuthorController(IAuthorRepository repository)
{
this.repository = repository;
}
[ResultLimit(20)]
public IQueryable<Author> GetAuthors(){
return repository.GetAuthors();
}
}
public class DBAuthorRepository : IAuthorRepository
{
public IQueryable<Author> GetAuthors()
{
using (var context = new QuotesDataContext())
{
return context.Authors.ToList().AsQueryable();
}
}
}
I found out that it was caused by deffered loading. So I added the following and now it works.
public class DBAuthorRepository : IAuthorRepository
{
public IQueryable<Author> GetAuthors()
{
using (var context = new QuotesDataContext())
{
context.DeferredLoadingEnabled = false; // Added this line
return context.Authors.ToList().AsQueryable();
}
}
}
i'm getting the above error in mvc4 webapi, form #alexandrekow answer, i found the solution:
entity = new BrewedlifeEntities();
entity.ContextOptions.ProxyCreationEnabled = false; // Added this line