当使用asp.net core和ef core时,我在调用add-migration init
时没有问题。但是当我在下面的控制台应用程序上应用相同的方法时,我收到一条错误消息:
Unable to create an object of type 'StudentContext'. Add an implementation of 'IDesignTimeDbContextFactory' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time.
解决此问题的最简单方法是什么?
.net core控制台应用项目如下:
应用设置.json
{
"ConnectionStrings": {
"Storage": "Data Source=storage.db"
}
}
EFCore.csproj
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>netcoreapp2.0</TargetFramework>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="Microsoft.EntityFrameworkCore" Version="2.0.1" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="2.0.1" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.0.1" />
<PackageReference Include="Microsoft.Extensions.Configuration" Version="2.0.0" />
<PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="2.0.0" />
<PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="2.0.0" />
</ItemGroup>
</Project>
学生.cs
namespace EFCore.Models
{
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
}
}
StudentContext.cs
要求:我不想通过默认无参数构造函数或OnConfiguring
方法在StudentContext
类中对连接字符串进行硬编码。
using Microsoft.EntityFrameworkCore;
namespace EFCore.Models
{
public class StudentContext : DbContext
{
public StudentContext(DbContextOptions<StudentContext> options) : base(options) { }
public DbSet<Student> Students { get; set; }
}
}
程序.cs
using EFCore.Models;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using System.IO;
namespace EFCore
{
class Program
{
static void Main(string[] args)
{
var configurationBuilder = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
IConfigurationRoot configuration = configurationBuilder.Build();
string connectionString = configuration.GetConnectionString("Storage");
DbContextOptionsBuilder<StudentContext> optionsBuilder = new DbContextOptionsBuilder<StudentContext>()
.UseSqlite(connectionString);
using (StudentContext sc = new StudentContext(optionsBuilder.Options))
{
sc.Database.Migrate();
sc.Students.AddRange
(
new Student { Name = "Isaac Newton" },
new Student { Name = "C.F. Gauss" },
new Student { Name = "Albert Einstein" }
);
sc.SaveChanges();
}
}
}
}
最佳答案
重要:不要将程序集命名为 ef
(或 eF
或 Ef
或 EF
) 来避免 this exception .
经过几个小时的努力,我找到了解决方案如下:
using EFCore.Models;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;
using Microsoft.Extensions.Configuration;
using System.IO;
namespace EFCore
{
class Program : IDesignTimeDbContextFactory<StudentContext>
{
public StudentContext CreateDbContext(string[] args)
{
var configurationBuilder = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
IConfigurationRoot configuration = configurationBuilder.Build();
string connectionString = configuration.GetConnectionString("Storage");
DbContextOptionsBuilder<StudentContext> optionsBuilder = new DbContextOptionsBuilder<StudentContext>()
.UseSqlite(connectionString);
return new StudentContext(optionsBuilder.Options);
}
static void Main(string[] args)
{
Program p = new Program();
using (StudentContext sc = p.CreateDbContext(null))
{
sc.Database.Migrate();
sc.Students.AddRange
(
new Student { Name = "Isaac Newton" },
new Student { Name = "C.F. Gauss" },
new Student { Name = "Albert Einstein" }
);
sc.SaveChanges();
}
}
}
}
我希望它对其他人也有用!
关于c# - 如何允许控制台应用程序迁移?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/48363173/