Question

我先使用EF代码 DomesticTask类看起来像

 public class DomesticTask
    {
        public int Id { get; set; }

        [Required]
        public ApplicationUser DomesticClient { get; set; }
        public DateTime DateTime { get; set; }

        [Required]
        [StringLength(500)]
        public string Description { get; set; }

        [Required]
        public Category Category { get; set; }
    }

类别类正在关注

{
    public int Id { get; set; }

    [Required]
    [StringLength(255)]
    public string Name { get; set; }
}

数据库上下文正在关注

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public DbSet<DomesticTask> DomesticTasks { get; set; }
    public DbSet<Category> Categories { get; set; }

我的迁移类看起来像这样

public partial class PopulateCategoriesTable : DbMigration
{
    public override void Up()
    {
        Sql("INSERT INTO Categories (Id, Name) VALUES (1, 'Plumber')");
        Sql("INSERT INTO Categories (Id, Name) VALUES (2, 'Mason')");
        Sql("INSERT INTO Categories (Id, Name) VALUES (3, 'Labour')");
        Sql("INSERT INTO Categories (Id, Name) VALUES (4, 'Milk-man')");
        Sql("INSERT INTO Categories (Id, Name) VALUES (5, 'Electrician')");
    }

    public override void Down()
    {
        Sql("DELETE FROM Categories WHERE Id IN (1, 2, 3, 4, 5)");
    }
}

当我执行update-database时，它会显示以下错误。

错误号：544，状态：1，类：16无法为其插入显式值表格中的标识列＆＃39;类别＆＃39;当IDENTITY_INSERT设置为 OFF。

如何解决错误？

Answer 1

您正在插入作为标识列的类别的Id的值，它应该由sql server插入。

Answer 2

您应该更新迁移脚本，以便在插入时设置identity列值。我当然假设您使用SQL Server作为数据存储，因为以下代码使用的是T-SQL而不是ANSI-92 SQL。

public partial class Seed_Categories : Migration
{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.Sql(@"
            SET IDENTITY_INSERT [dbo].[Categories] ON;

            INSERT INTO [dbo].[Categories] ([ID], [NAME], [CODE])
                VALUES
                    (1, 'Science Fiction',      'SCIFI'),
                    (2, 'Historical Fiction',   'HISFI'),
                    (3, 'Historical',           'HISTO'),
                    (4, 'English Literature',   'ENGLT'),
                    (5, 'Spanish Literature',   'SPALT');

            SET IDENTITY_INSERT [dbo].[Categories] OFF;
            ");
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {

    }
}

标识插入的错误解决方案已设置

2 个答案: