Erreur API Web: Le type 'ObjectContent`1' n'a pas réussi à sérialiser

Question

J'ai essayé de faire toutes les solutions possibles mais je n'ai toujours pas trouvé la bonne réponse. Ci-dessous mon code:

WebApiConfig.cs

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web.Http; 
using System.Net.Http.Headers; 

namespace WebAPI 
{ 
    public static class WebApiConfig 
    { 
     public static void Register(HttpConfiguration config) 
     { 
      // Web API configuration and services 

      // Web API routes 
      config.MapHttpAttributeRoutes(); 
      //test 
      var json = config.Formatters.JsonFormatter; 
      json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects; 
      config.Formatters.Remove(config.Formatters.XmlFormatter); 

      config.Routes.MapHttpRoute(
       name: "DefaultApi", 
       // routeTemplate: "api/{controller}/{id}", 
       routeTemplate: "institute/{controller}/{id}", 
       defaults: new { id = RouteParameter.Optional }   
      ); 

      //change xml to JSON output 
      // config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html")); 

     } 
    } 
} 

StudentController.cs

using System; 
using System.Collections.Generic; 
using System.Data; 
using System.Data.Entity; 
using System.Data.Entity.Infrastructure; 
using System.Linq; 
using System.Net; 
using System.Net.Http; 
using System.Web.Http; 
using System.Web.Http.Description; 
using WebAPI; 

namespace WebAPI.Controllers 
{ 
    public class StudentsController : ApiController 
    { 
     private InstituteEntities db = new InstituteEntities(); 

     // GET: api/Students 
     public IQueryable<Student> GetStudents() 
     { 
      return db.Students; 
     } 

     // GET: api/Students/5 
     [ResponseType(typeof(Student))] 
     public IHttpActionResult GetStudent(int id) 
     { 
      Student student = db.Students.Find(id); 
      if (student == null) 
      { 
       return NotFound(); 
      } 

      return Ok(student); 
     } 

     // PUT: api/Students/5 
     [ResponseType(typeof(void))] 
     public IHttpActionResult PutStudent(int id, Student student) 
     { 
      if (!ModelState.IsValid) 
      { 
       return BadRequest(ModelState); 
      } 

      if (id != student.Id) 
      { 
       return BadRequest(); 
      } 

      db.Entry(student).State = EntityState.Modified; 

      try 
      { 
       db.SaveChanges(); 
      } 
      catch (DbUpdateConcurrencyException) 
      { 
       if (!StudentExists(id)) 
       { 
        return NotFound(); 
       } 
       else 
       { 
        throw; 
       } 
      } 

      return StatusCode(HttpStatusCode.NoContent); 
     } 

     // POST: api/Students 
     [ResponseType(typeof(Student))] 
     public IHttpActionResult PostStudent(Student student) 
     { 
      if (!ModelState.IsValid) 
      { 
       return BadRequest(ModelState); 
      } 

      db.Students.Add(student); 

      try 
      { 
       db.SaveChanges(); 
      } 
      catch (DbUpdateException) 
      { 
       if (StudentExists(student.Id)) 
       { 
        return Conflict(); 
       } 
       else 
       { 
        throw; 
       } 
      } 

      return CreatedAtRoute("DefaultApi", new { id = student.Id }, student); 
     } 

     // DELETE: api/Students/5 
     [ResponseType(typeof(Student))] 
     public IHttpActionResult DeleteStudent(int id) 
     { 
      Student student = db.Students.Find(id); 
      if (student == null) 
      { 
       return NotFound(); 
      } 

      db.Students.Remove(student); 
      db.SaveChanges(); 

      return Ok(student); 
     } 

     protected override void Dispose(bool disposing) 
     { 
      if (disposing) 
      { 
       db.Dispose(); 
      } 
      base.Dispose(disposing); 
     } 

     private bool StudentExists(int id) 
     { 
      return db.Students.Count(e => e.Id == id) > 0; 
     } 
    } 
} 

Web.config

<?xml version="1.0" encoding="utf-8"?> 
<!-- For more information on how to configure your ASP.NET application, please visit http://go.microsoft.com/fwlink/?LinkId=301879 --> 
<configuration> 
    <configSections> 
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --> 
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" /> 
    </configSections> 
    <appSettings></appSettings> 
    <system.web> 
    <compilation debug="true" targetFramework="4.5.2" /> 
    <httpRuntime targetFramework="4.5.2" /> 
    </system.web> 
    <system.webServer> 
    <modules runAllManagedModulesForAllRequests="true"> 
     <remove name="WebDAVModule"/> 
     <!-- ADD THIS --> 
    </modules> 
    <handlers> 
     <remove name="ExtensionlessUrlHandler-Integrated-4.0" /> 
     <remove name="OPTIONSVerbHandler" /> 
     <remove name="TRACEVerbHandler" /> 
     <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" /> 
    </handlers> 
    </system.webServer> 
    <runtime> 
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"> 
     <dependentAssembly> 
     <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" /> 
     <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" /> 
     </dependentAssembly> 
     <dependentAssembly> 
     <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" /> 
     <bindingRedirect oldVersion="1.0.0.0-5.2.3.0" newVersion="5.2.3.0" /> 
     </dependentAssembly> 
     <dependentAssembly> 
     <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" /> 
     <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" /> 
     </dependentAssembly> 
    </assemblyBinding> 
    </runtime> 
    <system.codedom> 
    <compilers> 
     <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701" /> 
     <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+" /> 
    </compilers> 
    </system.codedom> 
    <connectionStrings> 
    <add name="InstituteEntities" connectionString="metadata=res://*/Institute.csdl|res://*/Institute.ssdl|res://*/Institute.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=BPWSVR01;initial catalog=Institute;persist security info=True;user id=sa;password=sa;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" /> 
    </connectionStrings> 
    <entityFramework> 
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework"> 
     <parameters> 
     <parameter value="mssqllocaldb" /> 
     </parameters> 
    </defaultConnectionFactory> 
    <providers> 
     <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" /> 
    </providers> 
    </entityFramework> 
</configuration> 

mon erreur est ci-dessous:

{ 
    "$id": "1", 
    "Message": "An error has occurred.", 
    "ExceptionMessage": "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.", 
    "ExceptionType": "System.InvalidOperationException", 
    "StackTrace": null, 
    "InnerException": { 
     "$id": "2", 
     "Message": "An error has occurred.", 
     "ExceptionMessage": "The ADO.NET provider with invariant name 'System.Data.SqlClient' is either not registered in the machine or application config file, or could not be loaded. See the inner exception for details.", 
     "ExceptionType": "System.ArgumentException", 
     "StackTrace":" at System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.<GetService>b__0(ArgumentException e, String n) 
      at System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetService(Type type, Object key, Func`3 handleFailedLookup) 
      at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory) 
      at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext() 
      at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) 
      at System.Data.Entity.Infrastructure.DependencyResolution.RootDependencyResolver.GetService(Type type, Object key) 
      at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext() 
      at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) 
      at System.Data.Entity.Infrastructure.DependencyResolution.CompositeResolver`2.GetService(Type type, Object key) 
      at System.Data.Entity.Infrastructure.DependencyResolution.DbDependencyResolverExtensions.GetService[T](IDbDependencyResolver resolver, Object key) 
      at System.Data.Entity.Core.EntityClient.EntityConnection.ChangeConnectionString(String newConnectionString) 
      at System.Data.Entity.Internal.LazyInternalConnection.InitializeFromConnectionStringSetting(ConnectionStringSettings appConfigConnection) 
      at System.Data.Entity.Internal.LazyInternalConnection.TryInitializeFromAppConfig(String name, AppConfig config) 
      at System.Data.Entity.Internal.LazyInternalConnection.Initialize()" 
    } 
} 

Answer 1

Regardez l'exception interne:

The ADO.NET provider with invariant name 'System.Data.SqlClient' is either not registered in the machine or application config file

Il est évident que votre problème est lié à Entity Framework: vous n'êtes pas correctement System.Data.SqlClient déployait ensemble sur votre serveur.

Ces questions peuvent vous aider à trouver comment résoudre ce problème:

• Entity Framework ADO.NET Sql.Data.Client provider not found
• ADO.NET provider with invariant name 'System.Data.SqlClient;' cannot be found (Entity Framework MVC)