在实体框架代码中，如何对多列使用 KeyAttribute

我正在创建一个 POCO 模型，首先用于实体框架代码 CTP5。我用这个装饰做了一个属性映射到一个 PK 列。但是如何在多个列上定义 PK，特别是如何控制索引中列的顺序？它是否是类中属性顺序的结果？

谢谢！

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最佳答案

You can specify the column order in the attributes, for instance:

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


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


[Key, Column(Order=2)]
public string MyThirdKeyProperty { get; set; }


// other properties
}

If you are using the Find method of a DbSet you must take this order for the key parameters into account.

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To complete the correct answer submitted by Slauma, you can use the HasKey method to specify an order for composite primary keys as well:

public class User
{
public int UserId { get; set; }
public string Username { get; set; }
}


public class Ctp5Context : DbContext
{
public DbSet<User> Users { get; set; }


protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<User>().HasKey(u => new
{
u.UserId,
u.Username
});
}
}
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If, like me, you prefer to use a configuration file you can do that in this way (based on Manavi's example):

public class User
{
public int UserId { get; set; }
public string Username { get; set; }
}


public class UserConfiguration : EntityTypeConfiguration<User>
{
public UserConfiguration()
{
ToTable("Users");
HasKey(x => new {x.UserId, x.Username});
}
}

Obviously you have to add the configuration file to your context:

public class Ctp5Context : DbContext
{
public DbSet<User> Users { get; set; }


protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new UserConfiguration());
}
}
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Use as a anonymous object:

modelBuilder.Entity<UserExamAttemptQuestion>().ToTable("Users").HasKey(o => new { o.UserId, o.Username });

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