Ef Core-使用Automapper从无键视图获取数据

如何解决Ef Core-使用Automapper从无键视图获取数据

我需要知道是否有可能使用Automapper从数据库视图映射DTO属性。也许在DbContext模型配置中是可能的。假设我有一个包含其他相关数据的视图是一个商业目的，但是为了简洁起见，我使类变得简单

相关Nugets

• EF Core v3.1.7
• AutoMapper v10.0.0

我有一个实体

public class Foo {
    public int Id { get; set; }
    public string Name { get; set; }
}

我有一个无钥匙视图

public class BarVW {
    public int FooId { get; set; }
    public string FooName { get; set; }
}

该视图内置于DB Initializer类中

context.Database.ExecuteSqlRaw(
    @"CREATE OR REPLACE VIEW v_Bar AS 
        select
            f.Id as FooId,f.[Name] as FooName
        from
            Foo f
        -- where some logic that makes a Foo appear in view"
);

然后将视图分配给DbContext类中的DbSet

modelBuilder.Entity<BarVW>(eb =>
    {
        eb.HasNoKey();
        eb.ToView("v_Bar");
    });

public DbSet<BarVW> BarVW { get; set; }

在我的FooDto中，我需要为实体类添加一个附加属性，以指示该Foo存在于数据库视图v_Bar

中。

public class FooDto {
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsBar { get; set; }
}

对于Automapper配置，我有以下内容，但是我不知道有什么方法可以从BarVW DbSet映射dto IsBar属性

CreateMap<Foo,FooDto>()
   .ForMember(dto => dto.IsBar,opt => ??? ); // don't know what to put here

解决方法

完成所需操作的一种简单方法是引入导航属性（例如Bars）并将其用于映射配置（例如opt.MapFrom(src => src.Bars.Any())）。

这是一个可以正常运行的示例控制台程序，它演示了这种方法：

using System.Diagnostics;
using System.Linq;
using AutoMapper;
using AutoMapper.QueryableExtensions;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

namespace IssueConsoleTemplate
{
    public class Foo
    {
        public int Id { get; set; }
        public string Name { get; set; }
        
        public BarVW Bar { get; set; }
    }

    public class BarVW
    {
        public int FooId { get; set; }
        public string FooName { get; set; }
        
        public Foo Foo { get; set; }
    }
    
    public class Context : DbContext
    {
        public virtual DbSet<Foo> Foo { get; set; }
        public virtual DbSet<BarVW> BarVW { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder
                .UseSqlServer(
                    @"Data Source=.\MSSQL14;Integrated Security=SSPI;Initial Catalog=So63850736")
                .UseLoggerFactory(LoggerFactory.Create(b => b
                    .AddConsole()
                    .AddFilter(level => level >= LogLevel.Information)))
                .EnableSensitiveDataLogging()
                .EnableDetailedErrors();
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Foo>()
                .HasData(
                    new Foo {Id = 1,Name = "Fo"},new Foo {Id = 2,Name = "Foo"},new Foo {Id = 3,Name = "Fooo"});

            modelBuilder.Entity<BarVW>(
                eb =>
                {
                    eb.HasKey(e => e.FooId);
                    eb.ToView("v_Bar");
                    eb.HasOne(e => e.Foo)
                        .WithOne(e => e.Bar)
                        .HasForeignKey<BarVW>(e => e.FooId);
                });
        }
    }
    
    public class FooDto
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public bool IsBar { get; set; }
    }

    internal static class Program
    {
        private static void Main()
        {
            using var context = new Context();

            context.Database.EnsureDeleted();
            context.Database.EnsureCreated();
            
            context.Database.ExecuteSqlRaw(
                @"CREATE VIEW [v_Bar] AS 
    select
        f.[Id] as [FooId],f.[Name] as [FooName]
    from
        [Foo] f
    where
        f.[Id] >= 1 and f.[Id] <= 2"
            );
            
            var config = new MapperConfiguration(
                cfg => cfg
                    .CreateMap<Foo,FooDto>()
                        .ForMember(dto => dto.IsBar,opt => opt.MapFrom(src => src.Bar != null)));
            
            var result = context.Foo
                .ProjectTo<FooDto>(config)
                .ToList();
            
            Debug.Assert(result.Count == 3);
            Debug.Assert(result.Count(dto => dto.IsBar) == 2);
        }
    }
}

为查询生成的SQL如下所示：

SELECT [f].[Id],CASE
    WHEN [v].[FooId] IS NOT NULL THEN CAST(1 AS bit)
    ELSE CAST(0 AS bit)
END AS [IsBar],[f].[Name]
FROM [Foo] AS [f]
LEFT JOIN [v_Bar] AS [v] ON [f].[Id] = [v].[FooId]

您可以使用.NET Fiddle运行示例代码。