Question 86394 in ASP.NET Question posted in
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Error with database – "Value cannot be null. Arg_ParamName_Name" – Asp.net

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?

Tags:

2

Answers


  1. 0

    Your AppSetting.json should be like this :

    "ConnectionStrings": {
      "DefaultConnection": "Server=(localdb)\MSSQLLocalDB;Database=u0925467_myblog;Trusted_Connection=true;MultipleActi 
       veResultSets=true"
  },
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  2. 0

    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"
  }
}
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