如何解决“实例故障”。 “更新数据库”

Question

我正在为我的应用程序设置非常基本的代码优先方法数据库上下文。我的解决方案下有MVC（UI）和类库（EntityFramework）项目。在Update-Database上收到错误Instance failure.

//迁移配置

internal sealed class Configuration : DbMigrationsConfiguration<UrfPractice.EntityFramework.UrfPracticeDbContext>
{
    public Configuration()
    {
        AutomaticMigrationsEnabled = true;
    }
}

//数据库上下文

public class UrfPracticeDbContext : DbContext
{
    static UrfPracticeDbContext()
    {
        Database.SetInitializer<UrfPracticeDbContext>(null);
    }
    public UrfPracticeDbContext() : base("name=DefaultConnectionString")
    {
    Configuration.AutoDetectChangesEnabled = true;
    Configuration.LazyLoadingEnabled = true;
    Configuration.ProxyCreationEnabled = false;
    }
    public DbSet<Entities.Customer> Customers { get; set; }
}

//客户迁移

public partial class Customer : DbMigration
{
    public override void Up()
    {
        CreateTable(
        "dbo.tblCustomers",
        c => new {
            Id = c.Int(nullable: false, identity: true),
            CustomerId = c.Int(nullable: false),
            Fullname = c.String(nullable: false, maxLength: 256)
        }).PrimaryKey(t => t.Id);
    }
    public override void Down()
    { DropTable("dbo.tblCustomers"); }
}

//实体类

[Table("tblCustomers")] public class Customer {
    [Key]
    public int CustomerId { get; set; }
    [MaxLength(250)]
    public string Fullname { get; set; }
}

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