System.ArgumentNullException: '值不能为空。 （参数'connectionString'）'2

Question

这行导致我的项目出错：

options.UseSqlServer(Configuration.GetConnectionString("SchoolContext")));

错误：

System.ArgumentNullException: '值不能为空。 (参数'connectionString')'

我已经在网上阅读了一堆类似的问题，但我找不到有效的更改。 UseSqlServer() 中的参数似乎返回 null。这让我相信我有一个配置错误。

这是我的启动文件和 json 文件的代码：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using ContosoUniversity.Data;

namespace ContosoUniversity
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddRazorPages();

            services.AddDbContext<SchoolContext>(options =>
               options.UseSqlServer(Configuration.GetConnectionString("SchoolContext")));

            services.AddDatabaseDeveloperPageExceptionFilter();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseMigrationsEndPoint();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapRazorPages();
            });
        }
    }
}

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=(***;Database=***;Trusted_Connection=True;MultipleActiveResultSets=true"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information",
      "Microsoft.EntityFrameworkCore.Database.Command": "Information"
    }
  },
  "AllowedHosts": "*"
}

感谢您提供任何帮助。谢谢。

Answer 1

您正在尝试获取一个名为SchoolContext 的连接字符串，但配置中只有一个名为DefaultConnection 的连接字符串。所以要么修复你的代码：

services.AddDbContext<SchoolContext>(options =>
           options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

或者修复你的配置：

{
  "ConnectionStrings": {
    "SchoolContext": "Server=....."
  },
  // etc...