System.ObjectDisposedException异常：Swagger过滤器中DbContext已释放问题

1. DbContext生命周期不匹配（核心问题） #

你在Program.cs的using块中创建了服务作用域，取出Senario01DbContext后直接传给OperationFilter。当using块结束时，作用域会被释放，内部的DbContext也会被自动Dispose。而Swagger的OperationFilter是单例生命周期，后续Swagger生成文档调用Apply方法时，持有的DbContext已经被释放，就会触发ObjectDisposedException。

2. 异步方法误用（次要问题） #

Apply方法使用了async void，这是C#异步编程的错误写法：异步操作会脱离当前上下文执行，无法保证DbContext在操作完成前不被释放，还会导致无法捕获异步异常。

方案一：通过IServiceProvider临时获取DbContext（通用兼容方案） #

修改过滤器，注入IServiceProvider，在Apply方法内临时创建作用域获取DbContext，用完自动释放：

public class AddCitiesToUserModelFilter : IOperationFilter
{
    private readonly IServiceProvider _serviceProvider; 

    public AddCitiesToUserModelFilter(IServiceProvider serviceProvider) 
    { 
        _serviceProvider = serviceProvider;
    }

    public void Apply(OpenApiOperation operation, OperationFilterContext context)
    {
        if (IsAddUserEndpoint(context))
        {
            using var scope = _serviceProvider.CreateScope();
            var dbContext = scope.ServiceProvider.GetRequiredService<Senario01DbContext>();
            
            // 修正：获取城市列表应该用Cities表，不是Customers表
            var cities = dbContext.Cities.ToList();

            var cityEnumSchema = new OpenApiSchema
            {
                Type = "integer",
                Enum = cities.Select(city => new OpenApiInteger(city.Id) as IOpenApiAny).ToList(),
            };

            operation.RequestBody.Content["application/json"].Schema.Properties["selectedCityId"] = cityEnumSchema;
        }
    }

    private bool IsAddUserEndpoint(OperationFilterContext context)
    {
        var httpMethod = context.ApiDescription.HttpMethod;
        var relativePath = context.ApiDescription.RelativePath;

        return httpMethod.Equals("POST", StringComparison.OrdinalIgnoreCase) &&
               relativePath.Contains("api/Home/AddUser");
    }
}

修改Program.cs的Swagger注册，让DI自动注入依赖，不再手动创建作用域：

builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "Your API", Version = "v1" });
    // 直接注册过滤器，无需手动传参
    c.OperationFilter<AddCitiesToUserModelFilter>();
});

方案二：使用EF Core的IDbContextFactory（推荐，符合EF最佳实践） #

如果使用EF Core 5及以上版本，推荐注册IDbContextFactory来创建独立的DbContext实例：

1. 先在Program.cs注册DbContextFactory：

builder.Services.AddDbContextFactory<Senario01DbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("YourConnectionString")));

2. 修改过滤器：

public class AddCitiesToUserModelFilter : IOperationFilter
{
    private readonly IDbContextFactory<Senario01DbContext> _contextFactory; 

    public AddCitiesToUserModelFilter(IDbContextFactory<Senario01DbContext> contextFactory) 
    { 
        _contextFactory = contextFactory;
    }

    public void Apply(OpenApiOperation operation, OperationFilterContext context)
    {
        if (IsAddUserEndpoint(context))
        {
            using var dbContext = _contextFactory.CreateDbContext();
            var cities = dbContext.Cities.ToList();

            var cityEnumSchema = new OpenApiSchema
            {
                Type = "integer",
                Enum = cities.Select(city => new OpenApiInteger(city.Id) as IOpenApiAny).ToList(),
            };

            operation.RequestBody.Content["application/json"].Schema.Properties["selectedCityId"] = cityEnumSchema;
        }
    }

    private bool IsAddUserEndpoint(OperationFilterContext context)
    {
        var httpMethod = context.ApiDescription.HttpMethod;
        var relativePath = context.ApiDescription.RelativePath;

        return httpMethod.Equals("POST", StringComparison.OrdinalIgnoreCase) &&
               relativePath.Contains("api/Home/AddUser");
    }
}

3. 同样在Program.cs中直接注册过滤器即可，无需手动传参。

你之前尝试仓储模式无效的原因：如果还是在Program.cs的using块中获取仓储实例传给过滤器，仓储内部持有的DbContext依然会随着作用域释放而被销毁，核心问题是过滤器生命周期与DbContext生命周期不匹配，而非是否使用仓储。

内容的提问来源于stack exchange，提问作者ari23yan