c# – 实体框架自定义数据类型映射

发布时间：2020-12-15 21:17:38 所属栏目：百科来源：网络整理

导读：鉴于此代码： public class Car { public virtual int CarId { get; set; } public virtual string TypeName { get; set; } public ConvertableNullabledouble Price { get; set; }} ConvertableNullable只是Nullable的一种解决方法,但它并不是从它继承的.

鉴于此代码：

public class Car 
{
    public virtual int CarId { get; set; }
    public virtual string TypeName { get; set; }
    public ConvertableNullable<double> Price { get; set; }
}

ConvertableNullable只是Nullable的一种解决方法,但它并不是从它继承的.

现在,这是我的简单上下文,我将汽车类映射到实体,并映射它的每个属性

public class MyDBContext : DbContext {
   public MyDBContext() : base(
       "data source=.;initial catalog=newDB1;integrated security=True;" + 
        "multipleactiveresultsets=True;App=EntityFramework")
   { }

   protected override void OnModelCreating(DbModelBuilder modelBuilder)
   {
       base.OnModelCreating(modelBuilder);

       modelBuilder.Entity<Car>().HasKey(x=>x.CarId);
       modelBuilder.Entity<Car>().Property(x => x.TypeName);
       modelBuilder.Entity<Car>().Property(x => x.Price);
   }

    public DbSet<Car> Cars { get; set; }
}

现在当我尝试处理这个上下文时,它会引发异常

var db = new MyDBContext();

// Throws exception "The property 'Price' is not a declared 
// property on type 'Car'. Verify that the property has not
// been explicitly excluded from the model by using the Ignore
// method or NotMappedAttribute data annotation. Make sure that
// it is a valid primitive property."
var c = db.Cars.ToList();

有什么建议？？

解决方法

唯一的解决方案是使用这样的东西：

public class Car 
{
    public virtual int CarId { get; set; }
    public virtual string TypeName { get; set; }
    // This must be accessible to the mapping 
    public double? PriceData { get; set; } 

    public ConvertableNullable<double> Price 
    { 
        get { // Return data from PriceData }
        set { // Set data to PriceData }
    }
}

您的映射将是：

modelBuilder.Entity<Car>().HasKey(x=>x.CarId);
modelBuilder.Entity<Car>().Property(x => x.TypeName);
modelBuilder.Entity<Car>().Property(x => x.PriceData).HasColumnName("Price");
modelBuilder.Entity<Car>().Ignore(x => x.Price);

问题是EF全局不支持自定义标量类型.

（编辑：李大同）

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