Blazor Server应用System.ObjectDisposedException异常排查求助

错误描述 #

System.ObjectDisposedException: 无法访问已释放的上下文实例。此错误的常见原因是将通过依赖注入解析的上下文实例释放后，又在应用的其他位置尝试使用同一实例。这可能是因为您调用了上下文实例的'Dispose'方法，或是将其包裹在using语句中。如果您使用依赖注入，应让依赖注入容器负责处理上下文实例的释放。
对象名称: 'MyDbContext'。

相关代码 #

模型类 #

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace SAPConnection.Data
{
    public class LeaveModel
    {
        [Key]
        public int Id { get; set; }
        public String Reason { get; set; } = "";
        public DateTime RequestDate { get; set; } = DateTime.Now;
        public DateTime ToDate { get; set; } = DateTime.Now;

        public DateTime FromDate { get; set; } = DateTime.Now;
        public LeaveTypeModel LeaveType { get; set; }
        [NotMapped]
        public byte[] Attachment { get; set; }
    }
}

public enum LeaveTypeModel
{
    Casual, Sick, Annual
}

LeaveService类 #

using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace SAPConnection.Data
{
    public class LeaveService
    {
        private readonly MyDbContext _context;

        public LeaveService(MyDbContext context)
        {
            _context = context;
        }

        public async Task<List<LeaveModel>> GetLeavesAsync()
        {
            return await _context.leaveModel.ToListAsync();
        }

        public async Task<LeaveModel> GetLeaveAsync(int id)
        {
            return await _context.leaveModel.FindAsync(id);
        }

        public async Task CreateLeaveAsync(LeaveModel leave)
        {
            _context.leaveModel.Add(leave);
            await _context.SaveChangesAsync();
        }

        public async Task UpdateLeaveAsync(LeaveModel leave)
        {
            _context.Entry(leave).State = EntityState.Modified;
            await _context.SaveChangesAsync();
        }

        public async Task DeleteLeaveAsync(int id)
        {
            var leave = await _context.leaveModel.FindAsync(id);
            _context.leaveModel.Remove(leave);
            await _context.SaveChangesAsync();
        }
    }
}

提交请假申请函数 #

private async Task submitLeaves()
{
    await leaveService.CreateLeaveAsync(newLeave);
    NavigationManager.NavigateTo("/");
}

Program.cs类 #

using Blazored.Toast;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Web;
using SAPConnection.Data;
using Microsoft.AspNetCore.Identity;
using Microsoft.EntityFrameworkCore;
using SAPConnection.Areas.Identity.Data;
using System.Configuration;

var builder = WebApplication.CreateBuilder(args);
var connectionString = builder.Configuration.GetConnectionString("SAPConnectionContextConnection") ?? throw new InvalidOperationException("Connection string 'SAPConnectionContextConnection' not found.");

builder.Services.AddDbContext<SAPConnectionContext>(options => options.UseSqlServer(connectionString));
builder.Services.AddDbContext<MyDbContext>(options => options.UseSqlServer(connectionString));
builder.Services.AddDefaultIdentity<ApplicationUser>(options => options.SignIn.RequireConfirmedAccount = true).AddEntityFrameworkStores<SAPConnectionContext>();
// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddSingleton<WeatherForecastService>();
builder.Services.AddScoped<LeaveService>();

builder.Services.AddBlazoredToast();
var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

app.UseHttpsRedirection();

app.UseStaticFiles();

app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();

app.MapBlazorHub();
app.MapFallbackToPage("/_Host");

app.Run();

问题排查与解决方案 #

核心原因 #

Blazor Server中，DbContext默认生命周期为Scoped，但Blazor的SignalR长连接作用域和ASP.NET Core传统请求作用域逻辑不同。如果MyDbContext被手动释放（如调用Dispose、用using块包裹创建），或服务/组件中错误管理了上下文生命周期，后续操作就会触发已释放异常。

具体修复步骤 #

1. 确认DbContext注册规范
   当前Program.cs中MyDbContext注册未显式指定生命周期，默认是Scoped，符合Blazor Server要求。可修改为显式注册，提升代码可读性：

   builder.Services.AddDbContext<MyDbContext>(options => options.UseSqlServer(connectionString), ServiceLifetime.Scoped);
   

2. 禁止手动管理DbContext生命周期
   检查所有使用MyDbContext的代码，确保没有调用_context.Dispose()，也没有手动new MyDbContext并在using块中使用的情况。依赖注入的上下文实例，生命周期完全由容器负责。

3. 组件注入方式校验
   确保组件中通过构造函数或属性注入LeaveService，禁止手动创建实例：

   // 组件中正确注入示例
   [Inject]
   public LeaveService leaveService { get; set; }
   [Inject]
   public NavigationManager NavigationManager { get; set; }
   

4. 优化SubmitLeaves方法
   确认newLeave对象无已释放上下文关联引用，NavigationManager.NavigateTo("/")跳转操作不会导致上下文释放，但需保证CreateLeaveAsync执行完成后无异步操作持有上下文引用。

5. 特殊场景：使用DbContext工厂
   若服务需在长生命周期组件中多次使用上下文，可改用IDbContextFactory<MyDbContext>创建实例，使用后手动释放：

   • 修改Program.cs注册：

     builder.Services.AddDbContextFactory<MyDbContext>(options => options.UseSqlServer(connectionString));
     

   • 修改LeaveService：

     public class LeaveService
     {
         private readonly IDbContextFactory<MyDbContext> _contextFactory;
     
         public LeaveService(IDbContextFactory<MyDbContext> contextFactory)
         {
             _contextFactory = contextFactory;
         }
     
         public async Task CreateLeaveAsync(LeaveModel leave)
         {
             using var context = _contextFactory.CreateDbContext();
             context.leaveModel.Add(leave);
             await context.SaveChangesAsync();
         }
         // 其他方法同理，用using块创建上下文
     }
     

内容的提问来源于stack exchange，提问作者abraKajapa