Entity Framework Core 2.0 mapping enum to tinyint in SQL Server throws exception on query

问题:

I get the following exception when I try to map an enum to smallint in OnModelCreating:

InvalidCastException: Unable to cast object of type 'System.Byte' to type 'System.Int32'.

I want to do this because in SQL Server an int is 4 bytes while a tinyint is 1 byte.

Relevant code: Entity:

namespace SOMapping.Data {     public class Tag     {         public int Id { get; set; }          public TagType TagType { get; set; }     }      public enum TagType     {         Foo,         Bar     } } 

DbContext:

using Microsoft.AspNetCore.Identity.EntityFrameworkCore; using Microsoft.EntityFrameworkCore;  namespace SOMapping.Data {     public class ApplicationDbContext : IdentityDbContext     {         public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)             : base(options)         {         }          public DbSet<Tag> Tags { get; set; }          protected override void OnModelCreating(ModelBuilder builder)         {             builder.Entity<Tag>().Property(m => m.TagType).HasColumnType("smallint");              base.OnModelCreating(builder);         }     } } 

Query:

using System.Linq; using Microsoft.AspNetCore.Mvc; using SOMapping.Data;  namespace SOMapping.Controllers {     public class HomeController : Controller     {         private ApplicationDbContext _applicationDbContext;          public HomeController(ApplicationDbContext applicationDbContext)         {             _applicationDbContext = applicationDbContext;         }          public IActionResult Index()         {             var tags = _applicationDbContext.Tags.ToArray();             return View();         }     } } 

Is there a way I can make this work so that I don't have to use 4 times as much space with all my enums?

回答1:

Base type of enum and type of column must be same. Start from changing base type for your enum:

public enum TagType: byte 

And your need remove

... .HasColumnType("smallint"); 

then column would be automaticaly tinyint, or set it manualy:

.HasColumnType("tinyint");  

文章来源: Entity Framework Core 2.0 mapping enum to tinyint in SQL Server throws exception on query