从ADO.net检索并创建webApi

Question

我正在尝试创建一个从azure上的sqlserver检索数据的webapi，我收到了这个错误。 我是asp.net webapi的新手这是我的第一次看到教程，我做了他正在做的事情，但我得到了这个错误

堆栈跟踪：

 at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType) 
at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithXsiTypeAtTopLevel(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle originalDeclaredTypeHandle, Type graphType) 
at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) 
at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) 
at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) 
at System.Runtime.Serialization.DataContractSerializer.WriteObject(XmlWriter writer, Object graph) 
at System.Net.Http.Formatting.XmlMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content) 
at System.Net.Http.Formatting.XmlMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken) --- End of stack trace from previous location where exception was thrown --- 
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
at System.Web.Http.WebHost.HttpControllerHandler.<WriteBufferedResponseContentAsync>d__1b.MoveNext()

我的控制器

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using DataBaseAccess;
namespace JoSaleWebApi.Controllers
{
public class BrandController : ApiController
{
   public IEnumerable<brand_Table> Get()
    {
        using (JoSaleDbEntities enitites = new JoSaleDbEntities())
        {
            return enitites.brand_Table.ToList();
        }

    }
    public brand_Table Get(int id)
    {
        using (JoSaleDbEntities enitites = new JoSaleDbEntities())
        {
            return enitites.brand_Table.FirstOrDefault(b => b.brand_id == id);
        }
    }
}}

ADO生成的课程

namespace DataBaseAccess
{
using System;
using System.Collections.Generic;

public partial class brand_Table
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public brand_Table()
    {
        this.branch_Table = new HashSet<branch_Table>();
        this.sale_Table = new HashSet<sale_Table>();
    }

    public int brand_id { get; set; }
    public string brand_name { get; set; }
    public string brand_imageUrl { get; set; }
    public int company_id { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<branch_Table> branch_Table { get; set; }
    public virtual company_Table company_Table { get; set; }
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<sale_Table> sale_Table { get; set; }
}

}

Answer 1

根据您的堆栈跟踪和代码，我发现您没有为您的实体应用DataContract，并且没有为XmlFormatter提供DataContractResolver。另一个问题是序列化与其他实体模型（company_Table）有关系的实体模型（brand_Table）。在将实体序列化为JOSN或xml时，此关系会导致自引用循环异常。要解决这些问题，可以在数据库上下文的构造方法中将LazyLoadingEnabled和ProxyCreationEnabled属性设置为false。

public JoSaleDbEntities()
        : base("name=JoSaleDbEntities ")
{
    this.Configuration.LazyLoadingEnabled = false;
    this.Configuration.ProxyCreationEnabled = false;
}