为什么我得到值不能为空。 (Parameter 'connectionString') 添加迁移后的错误消息

Question

我在尝试 Add-Migration 时收到错误消息，我收到错误消息

值不能为空。 (参数'connectionString')

到目前为止，我检查了 Startup.cs 文件并写了一些东西

using Microsoft.EntityFrameworkCore;
using ToDoS.Models;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");

builder.Services.AddDbContext<TodoContext>(opt =>
   opt.UseSqlServer(connectionString));

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

所以我添加了这部分

var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");

builder.Services.AddDbContext<TodoContext>(opt =>
   opt.UseSqlServer(connectionString));

这是我的连接字符串

{
  "Logging": {
    "ConnectionStrings": {
      "DefaultConnection": "Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=ToDoApp;Integrated Security=True"
    },
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*"
}

和 TodoContext

using Microsoft.EntityFrameworkCore;

namespace ToDoS.Models
{
    public class TodoContext : DbContext
    {
        public TodoContext(DbContextOptions<TodoContext> options) : base(options) { }
        public DbSet<Todo> Todos { get; set; }

    }
}

添加迁移 InitCreate 后我收到错误消息。我在哪里弄错了？我在这里缺少什么？

Answer 1

连接字符串在 appsettings.json 的 Logging 元素中定义。它应该在根元素中定义：

{
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=ToDoApp;Integrated Security=True"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*"
}

或者，您应该可以使用 GetValue:

获取字符串

var connectionString = builder.Configuration.GetValue<string>("Logging:ConnectionStrings:DefaultConnection");

为什么我得到值不能为空。 (Parameter 'connectionString') 添加迁移后的错误消息

Why I get Value cannot be null. (Parameter 'connectionString') error message after Adding Migrations

c#

asp.net-web-api

asp.net-core-mvc