c# - 如何捕获 EF 异常

Question

我想从 Entity Framework 中捕获错误。

所以我有下面的代码

 return await _context.SaveChangesAsync(cancellationToken);

如果上面的代码出现问题，我希望它在数据库中被捕获为警告，但截至目前它会自动保存在数据库中作为错误，实际上必须是警告。

下面是我得到的错误

An exception occurred in the database while saving changes for context type 'ValuationsReporting.Models.ValuationsReportingContext'. System.InvalidOperationException: The property 'TemplateTypeId' on entity type 'ValuationFundTemplate' has a temporary value. Either set a permanent value explicitly or ensure that the database is configured to generate values for this property. at Microsoft.EntityFrameworkCore.Update.Internal.CommandBatchPreparer.Validate(ModificationCommand modificationCommand) at Microsoft.EntityFrameworkCore.Update.Internal.CommandBatchPreparer.BatchCommands(IReadOnlyList1
entries)+MoveNext() at
Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(DbContext
_, ValueTuple2 parameters, CancellationToken cancellationToken) at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.ExecuteImplementationAsync[TState,TResult](Func4
operation, Func4 verifySucceeded, TState state, CancellationToken cancellationToken) at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.ExecuteImplementationAsync[TState,TResult](Func4
operation, Func4 verifySucceeded, TState state, CancellationToken cancellationToken) at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IReadOnlyList`1 entriesToSave, CancellationToken cancellationToken) at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken) at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)

System.InvalidOperationException

Microsoft.EntityFrameworkCore.Update

我尝试使用 try catch，但只要它转到那一行，错误就会记录在数据库中。

实际代码:

try
                {
                    foreach (var template in snapshotDto.SnapshopFundTemplateDtos)
                    {
                        if (template.FundId != null)
                        {
                            foreach (var fundId in template.FundId)
                            {
                                var tempTemplate = allFundTemplates.Where(x => x.ValuationId == valuation.Id && x.FundId == fundId && x.TemplateTypeId == template.TemplateTypeId).FirstOrDefault();

                                //var tempTemplate = await _valuationFundTemplateRepository.GetOne(valuation.Id, fundId, template.TemplateTypeId, true, cancellationToken);
                                if (tempTemplate == null)
                                {
                                    tempTemplate = new ValuationFundTemplate();
                                    tempTemplate.CreatedBy = _userRepository.claimsPrincipal.Identity.Name;
                                    tempTemplate.CreatedOn = DateTime.Now.ToUniversalTime();
                                    isTemplateUpdate = false;
                                }
                                //tempTemplate.IsDeleted = false;
                                //if (template.IsDeleted)
                                //{
                                //     _valuationFundTemplateRepository.Delete(tempTemplate);
                                //}
                                //else
                                //{
                                //tempTemplate.IsDeleted = template.IsDeleted;

                                tempTemplate.IsDeleted = false;
                                tempTemplate.IsDefaultFundTemplate = template.IsDefault;
                                tempTemplate.FundId = fundId;
                                tempTemplate.ValuationId = valuation.Id;
                                tempTemplate.TemplateTypeId = 0;
                                tempTemplate.TemplateId = template.TemplateId;
                                tempTemplate.ModifiedBy = _userRepository.claimsPrincipal.Identity.Name;
                                tempTemplate.ModifiedOn = DateTime.Now.ToUniversalTime();
                                tempTemplates.Add(tempTemplate);
                                if (isTemplateUpdate)
                                {
                                    _valuationFundTemplateRepository.Update(tempTemplate);
                                }
                                else
                                {
                                    await _valuationFundTemplateRepository.Insert(tempTemplate, cancellationToken);
                                }
                                //  }

                                await _valuationFundTemplateRepository.SaveAsync(cancellationToken);//here is where the error occurs which i dont want to capture in database.
                                if (!isTemplateUpdate)
                                    valuation.ValuationFundTemplate.Add(tempTemplate);
                            }

                        }
                    }
                }catch(Exception e)
                {
                    var z = e.Message;
                }



public virtual async Task<int> SaveAsync(CancellationToken cancellationToken = default(CancellationToken))
        {
            return await _context.SaveChangesAsync(cancellationToken);
        }

Answer 1

同意@PrashantPimpale 的意见，您可以简单地使用try catch。

但对于高级方法，我建议您可以使用全局错误处理中间件。通过它您可以捕获整个 dotnet API/应用程序中发生的任何错误。

下面只是详细说明:

// Extension method used to add the middleware to the HTTP request pipeline.
    public static class ErrorHandlingMiddlewareExtensions
    {
        public static IApplicationBuilder UseErrorHandlingMiddleware(this IApplicationBuilder builder)
        {
            return builder.UseMiddleware<ErrorHandlingMiddleware>();
        }
    }

然后在 Startup 的 Configure() 方法中添加 app.UseErrorHandlingMiddleware();。

您必须先创建一个 ErrorHandlingMiddleware 类。

 public class ErrorHandlingMiddleware
    {
        private readonly RequestDelegate _next;

        public ErrorHandlingMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task Invoke(HttpContext httpContext)
        {
            try
            {
                await _next(httpContext);
            }
            catch (Exception ex)
            {
                await HandleExceptionAsync(httpContext, ex);
            }
        }

        private static async Task HandleExceptionAsync(HttpContext context, Exception exception)
        {
          // Implement how you want to handle the error.
        }
}