Question

我有一个Asp_Users表和一个Resource表。在实体框架世界中，我有一个Asp_Users POCO和一个Resource POCO。此外，Resource POCO是抽象的，并且是Table-per-Hierarchy模型的一部分。 Table-per-Hierarchy模型具有抽象Resource POCO和几个Concrete POCO，如ILCResource POCO和SectionResource POCO。从Asp_Users POCO（单边）到Resource POCO（多边）之间存在一对多（1到0 ......）的关系。

这是我的aspnet_Users POCO的相关部分：

public partial class aspnet_Users
{
    public aspnet_Users() { }

    public virtual System.Guid ApplicationId { get; set; }
    public virtual System.Guid UserId { get; set; }
    public virtual string UserName { get; set; }
    public virtual string LoweredUserName { get; set; }
    public virtual string MobileAlias { get; set; }
    public virtual bool IsAnonymous { get; set; }
    public virtual System.DateTime LastActivityDate { get; set; }

    public virtual ICollection<Resource> associatedResources { get; set; }
}

这是我对Asp_Users的映射配置

public class Aspnet_UsersMap : EntityTypeConfiguration<PerlsData.Domain.aspnet_Users>
{
    public Aspnet_UsersMap()
    {
        this.ToTable("aspnet_Users", schemaName: "dbo");

        this.HasKey(u => u.UserId);

        this.Property(u => u.UserId)
            .HasColumnName("UserId")
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
        this.HasOptional(u => u.associatedResources);
    }
}

这是我的抽象资源POCO课程的相关部分：

public abstract class Resource
{   
    public Resource(){
       // associatedPerspectives = new HashSet<Perspective>();
    }

    public virtual System.Guid ResourceDatabaseID { get; set; }
    public virtual string ResourceName { get; set; }
    public virtual string DescriptionOfResource { get; set; }
    public virtual System.Guid UserId { get; set; }
    public virtual Nullable<System.Guid> DepartmentDatabaseID { get; set; }
    public virtual string ResourceStatus { get; set; }
    public virtual Nullable<short> isRemoved { get; set; }

    public virtual Department Department { get; set; }

    public virtual System.Guid UserId { get; set; }
    public virtual aspnet_Users aspnet_Users { get; set; }


    public virtual ICollection<ResourceOverToILCResourcesBridge> associatedResourceOverToILCResourcesBridgeEntry { get; set; }
}

这是我的资源的映射配置：

public class ResourceMap : EntityTypeConfiguration<Resource>
{

    public ResourceMap()
    {
        this.ToTable("Resources", schemaName: "dbo");

        this.Property(r => r.ResourceDatabaseID)
            .HasColumnName("ResourceDatabaseID");

        this.HasKey(r => r.ResourceDatabaseID);

        this.Property(x => x.ResourceDatabaseID)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
        // .StoreGeneratedPattern = StoreGeneratedPattern.Identity;
        this.Property(r => r.ResourceName)
            .HasColumnName("ResourceName");

        this.Map<PerlsData.Domain.OtherItem>(m => m.Requires("discriminator").HasValue("otheritems"))
        .Map<PerlsData.Domain.Audioitem>(m => m.Requires("discriminator").HasValue("audioitems"))
        .Map<PerlsData.Domain.Imageitem>(m => m.Requires("discriminator").HasValue("imageitems"))
        .Map<PerlsData.Domain.Videoitem>(m => m.Requires("discriminator").HasValue("videoitems"))
        .Map<PerlsData.Domain.UriItem>(m => m.Requires("discriminator").HasValue("uriitems"))
        .Map<PerlsData.Domain.Documentitem>(m => m.Requires("discriminator").HasValue("documentitems"))
        .Map<PerlsData.Domain.DatabaseFileItem>(m => m.Requires("discriminator").HasValue("databasefileitems"));

        this.HasOptional(res => res.associatedResourceOverToILCResourcesBridgeEntry);

        this.HasRequired(res => res.aspnet_Users)
            .WithMany(u => u.associatedResources)
            .HasForeignKey(res => res.UserId);
    }
}

您能否告诉我为什么会收到以下错误？

在类型上声明的导航属性“associatedResources” “PerlsData.Domain.aspnet_Users”已配置为冲突多重性。

请解释为什么在POCO类中创建映射后它仍为NULL。

enter image description here

Answer 1

this.HasOptional(u => u.associatedResources);

那是错的。 HasOptional表示0..1 你想要HasMany()。

事实上，你可以完全摆脱那条线; EF可以从房产中找到它。

Answer 2

我需要更多地了解IQueryable和/或IEnumerable集合以及用于检索数据的lambda表达式查询，并将它们放在前面提到的IQueryable和/中或IEnumerable。

我的问题是我试图在迭代IQueryable和/或IEnumerable集合的循环中检索特定POCO的关联。

这是有缺陷的代码（我们在迭代IQueryable时访问关联）：

resourcestempIQueryable = context.Resources;
foreach (PerlsData.Domain.Resource tempRes in resourcestempIQueryable)
{
    string[] resourceRow = { tempRes.ResourceName,
                             tempRes.DescriptionOfResource,
                             tempRes.UploadDate.ToString(),
                             tempRes.Iconpath,
                             tempRes.aspnet_Users.UserName, // Error
                             tempRes.ResourceDatabaseID.ToString() };
    tempDataTableForResources.Rows.Add(resourceRow);
}

以下是应该解决问题的正确代码：

using (PerlsData.Context context = new PerlsData.Context())
{
    context.Configuration.LazyLoadingEnabled = true;
    context.Configuration.ProxyCreationEnabled = true;
    resourcesIEnumerable = context.Resources.ToList<PerlsData.Domain.Resource>();

    var entityValuesWithFieldsToShowInAllResourcesPage = context.Resources.Select(res => new { res.ResourceName, res.DescriptionOfResource, res.UploadDate, res.Iconpath, res.aspnet_Users.UserName, res.ResourceDatabaseID });

    foreach (var varForIteratingOverEntityValuesWithFieldsToShowInAllResourcesPage in entityValuesWithFieldsToShowInAllResourcesPage)
    {
        string[] resourceRow = { 
            varForIteratingOverEntityValuesWithFieldsToShowInAllResourcesPage.ResourceName, 
            varForIteratingOverEntityValuesWithFieldsToShowInAllResourcesPage.DescriptionOfResource, 
            varForIteratingOverEntityValuesWithFieldsToShowInAllResourcesPage.UploadDate.ToString(), 
            varForIteratingOverEntityValuesWithFieldsToShowInAllResourcesPage.Iconpath, 
            varForIteratingOverEntityValuesWithFieldsToShowInAllResourcesPage.UserName, 
            varForIteratingOverEntityValuesWithFieldsToShowInAllResourcesPage.ResourceDatabaseID.ToString()
        };
        tempDataTableForResources.Rows.Add(resourceRow);
    }
}

为什么导航属性''在类型'上声明'已经配置了冲突的多重性。出现错误？

2 个答案: