Question

我首先要掌握EF4代码，并且喜欢它到目前为止。但是我无法将实体映射到具有复合主键的表。

我尝试过的配置如下：

public SubscriptionUserConfiguration()

    {
                Property(u => u.SubscriptionID).IsIdentity();
                Property(u => u.UserName).IsIdentity();
    }

抛出此异常：无法推断实体类型'SubscriptionUser'的密钥。

我错过了什么？

Answer 1

您也可以使用

HasKey(u => new { u.SubscriptionID, u.UserName });

编辑：

我发现的一个限制是以下不起作用：

public ProjectAssignmentConfiguration()
{
    HasKey(u => u.Employee.EmployeeId);
    HasKey(u => u.Project.ProjectId);
}

或

public ProjectAssignmentConfiguration()
{
    HasKey(u => new { u.Employee.EmployeeId, u.Project.ProjectId });
}

那么如何设置一个实体，其中连接表有一个由外键组成的主键？

Answer 2

我将尝试使用以下实体逐步解释它

public class Account
{
    public int AccountId1 { get; set; }
    public int AccountId2 { get; set; }
    public string Description { get; set; }
}

创建一个派生自EntityTypeConfiguaration<TEntity>对象的类以覆盖约定

class AccountEntityTypeConfiguration : EntityTypeConfiguration<Account>
{

    public AccountEntityTypeConfiguration()
    {
      // The Key
      // The description of the HasKey Method says
      // A lambda expression representing the property to be used as the primary key.
      // If the primary key is made up of multiple properties then specify an anonymous type including the properties.
      // Example C#: k => new { k.Id1, k.Id2 }
      // Example VB: Function(k) New From { k.Id1, k.Id2 }
      this.HasKey(k => new { k.AccountId1, k.AccountId2 } );  // The Key

      // Maybe the key properties are not sequenced and you want to override the conventions
      this.Property(p => p.AccountId1).HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.None);
      this.Property(p => p.AccountId2).HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.None);

      this.Property(p => p.Description).IsRequired();  // This property will be required
      this.ToTable("Account");  // Map the entity to the table Account on the database
    }
}

创建从DbContext对象派生的类时，重写OnModelCreating方法并将新的AccountEntityTypeConfiguration对象添加到模型构建器的配置中。

public class MyModelAccount : DbContext
{
    public DbSet<Account> Accounts { get; set;}

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // Add a new AccountEntityTypeConfiguration object to the configuration of the model, that will be applied once the model is created. 
        modelBuilder.Configurations.Add(new AccountEntityTypeConfiguration());
    }

}

希望它可以帮到你！

Answer 3

您还可以使用Column属性

public class UserProfileRole
{
    [Key, Column(Order = 0)]
    public int UserId { get; set; }

    [Key, Column(Order = 1)]
    public int RoleId { get; set; }
}

Answer 4

解决它：我应该使用HasKey，而不是身份。这有效：

public SubscriptionUserConfiguration()
{
     HasKey(u => u.SubscriptionID);
     HasKey(u => u.UserName);
}

如何首先在Entity Framework 4代码中映射复合主键？

4 个答案: