EF 4.1 Fluent API dB first 关系映射问题答案

【问题标题】：EF 4.1 Fluent API dB first relationship mapping problemEF 4.1 Fluent API dB first 关系映射问题
【发布时间】：2011-04-09 01:01:20
【问题描述】：

我有以下表格，

产品(pro_iIDX[PK], pro_sName)
制造商(man_iIDX[PK], man_sName)
ProductManufacturer(pma_iIDX[PK], pma_iProductRef[FK], pma_iManufacturerRef[FK], pma_bAvailable)

我有以下 POCO，

public class ProductInfo  
{  
    public int IDX { get; set; }  
    public string Name { get; set; }

    public virtual ICollection<ProductManufacturerInfo> C0ProductManufacturers 
        { get; set; }  
}  

public class ManufacturerInfo  
{  
    public int IDX { get; set; }  
    public string Name { get; set; }  

    public virtual ICollection<ProductManufacturerInfo> C0ProductManufacturers 
        { get; set; }  
}  

public class ProductManufacturerInfo  
{  
    public int IDX { get; set; }  
    public bool Available { get; set; }  

    public virtual ManufacturerInfo C0Manufacturer { get; set; }  
    public virtual ProductInfo C0ProductInfo { get; set; }  
}

我使用了以下映射但没有成功，

public ProductManufacturerConfiguration()  
{  
    ToTable("ProductManufacturer");  
    HasKey(p => p.IDX);  
    Property(p => p.IDX).HasColumnName("pma_iIDX");  
    Property(p => p.Available).HasColumnName("pma_bAvailable");  
    Property(p => p.ProductRef).HasColumnName("pma_iProductRef");  
    Property(p => p.ManufacturerRef).HasColumnName("pma_iManufacturerRef");  

    //I have tried  
    HasRequired(p => p.ManufacturerInfo)
            .WithMany(c => c.C0ProductManufacturers)
            .Map(m => m.MapKey("pma_iManufacturerRef"));  
    HasRequired(p => p.ProductInfo)
            .WithMany(c => c.C0ProductManufacturers)
            .Map(m => m.MapKey("pma_iProductRef"));  

    //As well as  
    HasRequired(p => p.C0Manufacturer)
            .WithMany(c => c.C0ProductManufacturers)
            .HasForeignKey(p => p.ManufacturerRef);  
    HasRequired(p => p.C0Product)
            .WithMany(c => c.C0ProductManufacturers)
            .HasForeignKey(p => p.C0Product);
}

在我的试验中，当我执行以下操作时，dB 首先抱怨找不到ManufacturerInfo_IDX，

var query = from p in _context.Product  
    select p;

如果我走代码优先路线，则会创建下表，

ProductManufacturer(
            pma_iIDX[PK], 
            pma_iProductRef, 
            pma_iManufacturerRef, 
            pma_bAvailable, 
            ManufacturerInfo_IDX, 
            ProductInfo_IDX)

我们将不胜感激。

【问题讨论】：

发生异常时您实际执行了哪些代码？您的 ProductManufacturerConfiguration 甚至无法使用您在上面提供的 POCO 类进行编译。您能否编辑您的问题以明确哪些代码不起作用？

标签： c# entity-framework-4.1 fluent-interface database-first

【解决方案1】：

我几乎不相信您提供的示例是您的真实代码，因为它甚至无法编译。复制一个真实的代码来显示一个问题就这么难吗？

这行得通：

public class ProductInfo
{
    public int IDX { get; set; }
    public string Name { get; set; }

    public virtual ICollection<ProductManufacturerInfo> C0ProductManufacturers
    { get; set; }
}

public class ManufacturerInfo
{
    public int IDX { get; set; }
    public string Name { get; set; }

    public virtual ICollection<ProductManufacturerInfo> C0ProductManufacturers
    { get; set; }
}

public class ProductManufacturerInfo
{
    public int IDX { get; set; }
    public bool Available { get; set; }

    public int ManufacturerRef { get; set; }        
    public virtual ManufacturerInfo C0Manufacturer { get; set; }

    public int ProductRef { get; set; }
    public virtual ProductInfo C0ProductInfo { get; set; }
}

public class ProductManufacturerConfiguration : EntityTypeConfiguration<ProductManufacturerInfo>
{
    public ProductManufacturerConfiguration()  
    {  
        ToTable("ProductManufacturer");  
        HasKey(p => p.IDX);  
        Property(p => p.IDX).HasColumnName("pma_iIDX");  
        Property(p => p.Available).HasColumnName("pma_bAvailable");
        Property(p => p.ProductRef).HasColumnName("pma_iProductRef");
        Property(p => p.ManufacturerRef).HasColumnName("pma_iManufacturerRef");  

        //I have tried  
        HasRequired(p => p.C0Manufacturer)
                .WithMany(c => c.C0ProductManufacturers)
                .Map(m => m.MapKey("pma_iManufacturerRef"));
        HasRequired(p => p.C0ProductInfo)
                .WithMany(c => c.C0ProductManufacturers)
                .Map(m => m.MapKey("pma_iProductRef"));  

        //As well as  
        HasRequired(p => p.C0Manufacturer)
                .WithMany(c => c.C0ProductManufacturers)
                .HasForeignKey(p => p.ManufacturerRef);  
        HasRequired(p => p.C0ProductInfo)
                .WithMany(c => c.C0ProductManufacturers)
                .HasForeignKey(p => p.ProductRef);
    }
}

【讨论】：

【解决方案2】：

主要问题是您的 ProductManufacturerInfo 的密钥不应该是 IDX。 IDX 更像是您的多对多关联中的“有效负载”。解决这个问题的一种方法是指定一个真正的键，然后映射很容易：

public class ProductManufacturerInfo
{
    public int IDX { get; set; }
    public bool Available { get; set; }

    public int C0ManufacturerIDX { get; set; }
    public virtual ManufacturerInfo C0Manufacturer { get; set; }

    public int C0ProductInfoIDX { get; set; }
    public virtual ProductInfo C0ProductInfo { get; set; }
}

然后你的映射：

public class ProductManufacturerConfiguration 
    : EntityTypeConfiguration<ProductManufacturerInfo>
{
    public ProductManufacturerConfiguration()
    {
        ToTable("ProductManufacturer");
        HasKey(p => new { p.C0ManufacturerIDX, p.C0ProductInfoIDX });
        Property(p => p.IDX)
           .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
    }
}

【讨论】：