Question

我有一个带有一些属性和行为的基类。此基类由许多其他类扩展/继承。其中一些类应该在它们自己的属性之一和基类的一个属性上创建唯一的多列索引。

public class BaseClass
{ 
    long employeeId {get; set;}
    // and many other things...
}

public class Buzzword : BaseClass
{
    string Name {get;set;} // supposed to be unique for every employee
    // many other things...
}

我现在想要的是这样的，重复我的Buzzword课程：

public class Buzzword : BaseClass
{
    [Index("IX_Buzzword_EmployeeId_Name", IsUnique = true, Order = 1]
    // black magic: inherited property of BaseClass
    [Index("IX_Buzzword_EmployeeId_Name", IsUnique = true, Order = 2]
    string Name {get;set;} // supposed to be unique for every employee
    // many other things...
}

我该怎么做？使employeeId成为虚拟的（因此仍在所有子类中实现）并在类中覆盖它以进行多列索引定义（以及对基本实现的调用）？

亲切的问候，伴侣

Answer 1

如果基类包含多列索引中需要的列，则必须跳过使用注释并使用EntityTypeConfiguration作为映射。

所以在你的DbContext中，你可以这样做：

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<BuzzWord>().Property(b => b.EmployeeId).HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("IX_Buzzword_EmployeeId_Name", 1)));
        modelBuilder.Entity<BuzzWord>().Property(b => b.Name).HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("IX_Buzzword_EmployeeId_Name", 2)));
        base.OnModelCreating(modelBuilder);
    }

或者，如果您不喜欢用大量的映射代码污染您的DbContext，您可以创建一个映射类并告诉您的上下文加载所有这些：

public class BuzzWordMapping : EntityTypeConfiguration<BuzzWord>
{
    public BuzzWordMapping()
    {
        Property(b => b.EmployeeId).HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("IX_Buzzword_EmployeeId_Name", 1)));
        Property(b => b.Name).HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("IX_Buzzword_EmployeeId_Name", 2)));
    }
}

然后你的OnModelCreating会是这样的：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //  This should include any mappings defined in the same assembly as the BuzzWordMapping class
        modelBuilder.Configurations.AddFromAssembly(typeof(BuzzWordMapping).Assembly);
        base.OnModelCreating(modelBuilder);            
    }

继承的，未覆盖的字段

1 个答案: