I do a project in ASP.NET Core 6.0 and try to connect a database.

Program.cs:

using ClanSS.Data;
using ClanSS.Data.Repository;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllersWithViews();
builder.Services.AddScoped<IRepository, Repository>();
builder.Services.AddDbContext<AppDbContext>(options =>
   { 
       options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"));
   });

var app = builder.Build();

if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Home/Error");
    app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.MapControllerRoute(name: "default", pattern: "{controller=Home}/{action=Index}/{id?}");
app.Run();

AppDbContext.cs

using ClanSS.Models;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;

namespace ClanSS.Data
{
    public class AppDbContext : DbContext
    {
        public AppDbContext(DbContextOptions<AppDbContext> options)
         : base(options)
        { Database.EnsureCreated(); }
        public DbSet<Post> Posts { get; set; } 
        public DbSet<Player> Team { get; set; }
    }
}

appsettings.json:

{
"DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=u0925467_myblog;Trusted_Connection=true;MultipleActiveResultSets=true"
}

When I launch the project, the string in Startup is highlighted: options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"));. And the follow error is shown:

Value cannot be null. Arg_ParamName_Name

What's wrong?

CodePudding user response：

Your AppSetting.json should be like this :

"ConnectionStrings": {
      "DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=u0925467_myblog;Trusted_Connection=true;MultipleActi 
       veResultSets=true"
  },

CodePudding user response：

This should be an error caused by not being able to get your DefaultConnection, it may be that your ConnectionStrings are in the wrong location.

appsetting.json should look like this：

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=u0925467_myblog;Trusted_Connection=true;MultipleActiveResultSets=true"
  }
}