ASP.Net 5升级至7后userManager.FindByNameAsync()抛出空值异常

异常现象 #

• 从ASP.NET 5升级到ASP.NET 7后，调用userManager.FindByNameAsync("Admin")时抛出SqlNullValueException，提示"Data is Null. This method or property cannot be called on Null values."
• 该方法在ASP.NET 5中正常运行，传入参数正确，但执行时直接报错终止调试
• 目标用户由userManager.CreateAsync()创建

关键代码片段 #

User模型 #

namespace API.Models
{
    public class User : IdentityUser<int>
    {
        public string FirstName { get; set; }

        //********** Visa Info**********
        public string ClientName { get; set; }
        public string BankName { get; set; }
        public int AccountNumber { get; set; }
        public string Section { get; set; }
        public int CardNumber { get; set; }
        public string CardName { get; set; }
        public int WalletNumber { get; set; }
        public string lastName { get; set; }
        public string address { get; set; }
        public string ImageID { get; set; } 
        public int TotalProfits { get; set; } = 0;
        public int WithdrawnProfits { get; set; } = 0;

        public virtual ICollection<Product> Products { get; set; }
        public virtual ICollection<Order> Orders { get; set; }
        public ICollection<UserRole> UserRoles { get; set; }
        public ICollection<WithdrawRequest> WithdrawRequests { get; set; }
        public virtual ICollection<UserBill> UserBills { get; set; }
    }
}

调用方法代码 #

private async Task CreateAdmin()
{
    var admin = await _userManager.FindByNameAsync("Admin");

    if (admin == null)
    {
        var newUser = new User
        {
            Email = "admin@admin.com",
            UserName = "Admin",
            PhoneNumber = "0796544854",
            EmailConfirmed = true
        };

        var createAdmin = await _userManager.CreateAsync(newUser, "1234");

        if (createAdmin.Succeeded)
        {
            if (await _roleManager.RoleExistsAsync("Admin"))
                await _userManager.AddToRoleAsync(newUser, "Admin");
        }

        var newShippCompany = new ShippingCompany
        {
            Id = 1,
            companyName = "Not Attached",
            companyPhone = null
        };

        await _souqlyRepo.Add(newShippCompany);
        await _souqlyRepo.SaveAll();
    }
}

完整异常栈 #

{System.Data.SqlTypes.SqlNullValueException: Data is Null. This method or property cannot be called on Null values.
   at Microsoft.Data.SqlClient.SqlBuffer.ThrowIfNull()
   at Microsoft.Data.SqlClient.SqlBuffer.get_String()
   at Microsoft.Data.SqlClient.SqlDataReader.GetString(Int32 i)
   at lambda_method42(Closure, QueryContext, DbDataReader, ResultContext, SingleQueryResultCoordinator)
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()
   at Microsoft.EntityFrameworkCore.Query.ShapedQueryCompilingExpressionVisitor.SingleOrDefaultAsync[TSource](IAsyncEnumerable`1 asyncEnumerable, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.ShapedQueryCompilingExpressionVisitor.SingleOrDefaultAsync[TSource](IAsyncEnumerable`1 asyncEnumerable, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Identity.UserManager`1.FindByNameAsync(String userName)
   at API.Controllers.AuthController.CreateAdmin() in /Users/ahmedgamal/projects/API/Controllers/AuthController.cs:line 84
   at API.Controllers.AuthController.Login(UserForLogin userForLogin) in /Users/ahmedgamal/projects/API/Controllers/AuthController.cs:line 149
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(ActionContext actionContext, IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
   at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

HEADERS
=======
Accept: */*
Connection: keep-alive
Host: localhost:5077
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.9
Content-Type: application/json-patch+json
Cookie: _xsrf=2|7ddc8933|478e981c349410ca2e05fa7b50dcaeee|1671139281; username-localhost-8888="2|1:0|10:1671456298|23:username-localhost-8888|44:NjA1OTkxOTgzZjFhNDE1MWFhOTIxNWQ3ZDczZjU1MjY=|5ae71afcdb82e897faa88c8158ab4ccb4edfbe7e4478f2e6dc88926938171b11"; .AspNetCore.Antiforgery._EomAn3AoJg=CfDJ8Oe9S8Poye1KncOFEtdCmBpov-Z4Szk20KKrAQTFIPoPKPabF-KF8zohP-BZVw8pL_FKLxPvrlxXrZt5K5SBF3YB9-5Lul_q0outcr2kZgyc4glteG-JGf8j0_pq2-a0_DN9WupHrzZo3igvLzqBsoQ; .AspNetCore.Session=CfDJ8Oe9S8Poye1KncOFEtdCmBr0c19qm2tGMZe7b6rkQbgsvt77HALStTx0XC86brZHEp8kf6YdM46RUT1wt0K6Wfa7mMXMXHE58ap382sIuQOtujORzTAnlBVLypOYMuJTwj%2BLmJ4lrUHWyY98ViOI9UdtLv1N6Nifn4%2BfUZE2I9QM
Origin: http://localhost:5077
Referer: http://localhost:5077/swagger/index.html
Content-Length: 116
sec-ch-ua: "Not?A_Brand";v="8", "Chromium";v="108", "Google Chrome";v="108"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "macOS"
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
}

原因分析 #

1. 值类型字段的Null兼容性问题：User模型中AccountNumber、CardNumber、WalletNumber为非可空int类型，但数据库中这些字段存在Null值。ASP.NET 7对应的EF Core 7.0对值类型的Null处理更严格，读取Null值到非可空值类型时直接抛出异常；而ASP.NET 5使用的EF Core 5.0会默认将Null转换为值类型默认值（如0），不会报错。
2. 数据与模型不匹配：升级后数据库结构未同步，或旧数据中存在这些值类型字段为Null的记录，导致查询时无法完成映射。

解决方法 #

方法1：修改模型字段为可空类型 #

将User模型中的非可空int字段改为可空int?，允许数据库Null值映射到模型：

public int? AccountNumber { get; set; }
public int? CardNumber { get; set; }
public int? WalletNumber { get; set; }

修改后生成并执行数据库迁移，更新表结构允许这些字段为Null。

方法2：填充数据库中的Null值 #

如果业务要求这些字段不能为Null，需检查数据库中已有用户记录，将这些int类型字段的Null值填充为合理默认值（如0），确保模型与数据一致。

方法3：调整EF Core配置 #

检查DbContext中是否对这些字段设置了IsRequired()，若业务允许，移除该配置或改为IsRequired(false)。

额外优化 #

创建用户时补充这些值类型字段的默认值（当前CreateAdmin方法中未设置这些字段，导致数据库中为Null），后续新增用户时添加必填校验或默认值赋值逻辑。

内容的提问来源于stack exchange，提问作者Ahmed Gamal