ef-core-3.0

问题 I have this MyEntity table in the database: The data inside MyEntity is the following: The EF Core entity is the following: public class MyEntity { public int Id { get; set; } public int MyInt { get; set; } } I am getting an exception: System.Data.SqlTypes.SqlNullValueException: 'Data is Null. This method or property cannot be called on Null values.' when trying to load the MyEntity from the DbContext : var myEntities = dbContext.Set<MyEntity>.ToList(); What am I doing wrong? 回答1: You are

问题 I'm trying to implement an abstract class for CRUD objects which contains two references to the User class; one for the User which created the object and the other for the User which last modified it. Entity framework is unable to determine the relationship represented by the CreatedBy and ModifiedBy navigation properties on the class inheriting them (Department). A potential additional complication is that the User class also has a property of class Department, which is unrelated to the

问题 In ef core 2.2 I have used DbQuery to map raw sql results to object as following: public partial class AppDbContext{ public DbQuery<SimpleQueryModel> SimpleQM {get;set;} } and then var result=_dbContext.SimpleQM.FromSql(sqlString,params); this wouldn't create any extra table and working just fine. In ef core 3.1 DbQuery is obsolete and telling me to use keyless DbSet instead. I have configured it as following: public partial class AppDbContext{ public DbSet<SimpleQueryModel> SimpleQM {get;set

问题 Currently testing with EF Core version 3.1.1. When I search, I find references to this problem, but I don't see any definitive answers about why this happens, and whether it is a bug that will be fixed or if it's expected behavior. This is just as simple as it looks--the BatchRequest table/entity has an integer column/property called BatchId: var batchRequestGroups = context.BatchRequests.GroupBy(br => br.BatchId).ToList(); When I run this, I get a System.InvalidOperationException, "Client

问题 Currently testing with EF Core version 3.1.1. When I search, I find references to this problem, but I don't see any definitive answers about why this happens, and whether it is a bug that will be fixed or if it's expected behavior. This is just as simple as it looks--the BatchRequest table/entity has an integer column/property called BatchId: var batchRequestGroups = context.BatchRequests.GroupBy(br => br.BatchId).ToList(); When I run this, I get a System.InvalidOperationException, "Client

问题 I have been reading that Repositories should return domain objects only. I am having difficulty with implementing this. I currently have API with Service Layer, Repository and I am using EF Core to access sql database. If we consider User(Id, Name, address, PhoneNumber, Email, Username) and Orders (id, OrderDetails, UserId) as 2 domain objects. One Customer can have multiple Orders. I have created navigation property public virtual User User{ get; set; } and foreign Key. Service layer needs

问题 I need to execute a complex sql query in entity framework core 3.1.1, on researching i found out that keyless entity types is the way to go in code first approach. I see lot of documents for dbquery but this is marked as obsolete in .net core 3.x keyless entity types As per Microsoft documentation it says dbquery is obsolete so use dbset approach instead, but with dbset it is trying to create a new table in database. how to disable table generation in keyless entity types while applying

问题 In EF Core 2.2 I had: var data = await _ArticleTranslationRepository.DbSet .Include(arttrans => arttrans.Article) .ThenInclude(art => art.Category) .Where(trans => trans.Article != null && trans.Article.Category != null && trans.Article.Category.Id == categoryId.Value) .GroupBy(trans => trans.ArticleId) .Select(g => new { ArticleId = g.Key, TransInPreferredLang = g.OrderByDescending(trans => trans.LanguageId == lang).ThenByDescending(trans => trans.LanguageId == defaultSiteLanguage).ThenBy

问题 In EF Core 2.2 I had: var data = await _ArticleTranslationRepository.DbSet .Include(arttrans => arttrans.Article) .ThenInclude(art => art.Category) .Where(trans => trans.Article != null && trans.Article.Category != null && trans.Article.Category.Id == categoryId.Value) .GroupBy(trans => trans.ArticleId) .Select(g => new { ArticleId = g.Key, TransInPreferredLang = g.OrderByDescending(trans => trans.LanguageId == lang).ThenByDescending(trans => trans.LanguageId == defaultSiteLanguage).ThenBy

问题 I am having "TimeClocked" in my database table in the format HH.mm and I want to sum all the "TimeClocked" using LINQ. I have tried this aggregate function. var data = _projectDbContext .Tasks .Where(x => x.Project.CompanyId == companyId && x.Status == true) .Select(e => TimeSpan.Parse(e.TimeClocked)) .Aggregate(TimeSpan.FromMinutes(0), (total, next) => total + next) .ToString(); I am using EF Core 3.0.0 . It's showing error like this. Processing of the LINQ expression 'Aggregate<TimeSpan,