entity-framework-core

问题 How can I combine BinaryExpression and Expression<Func<dynamic / T, bool>> ? For example: void AddGlobalFilter<T>(Expression<Func<T, bool>> expr) { var parameter = Expression.Parameter(type, "t"); var member = Expression.Property(filter.Parameter, field); var constant = Expression.Constant(null); var body = Expression.Equal(member, constant); var combine = Expression.AndAlso(body, expr); } I am trying to define global filter for Entity Framework (EF) Core. The problem is I must manually

问题 Can a relationship one-to-one be created only one way? public class Class1 { [Key] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Class1Id { get; set; } ... } public class Class2 { [Key] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Class2Id { get; set; } public int? RelationshipId { get; set; } public virtual Class1 Relationship { get; set; } ... } And the configuration looks like this public void Configure(EntityTypeBuilder<Class2> builder) { builder

问题 Can a relationship one-to-one be created only one way? public class Class1 { [Key] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Class1Id { get; set; } ... } public class Class2 { [Key] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Class2Id { get; set; } public int? RelationshipId { get; set; } public virtual Class1 Relationship { get; set; } ... } And the configuration looks like this public void Configure(EntityTypeBuilder<Class2> builder) { builder

问题 We are porting an ASP.NET MVC 4.x application to ASP.NET Core 3.1 . The current application is using EF 6.x DB first approach. As a part of this migration we are going to use EF Core 3.1 as an alternative to the current EF 6.x . So the question is: Does EF Core 3.1 support DB First approach? If not, what are the options? Are we left with only code first approach? Appreciate your helps. 回答1: Yes. It supports DB First Approach since .NET Core 1.0 until now. You need to download 4 from nugets

问题 Creating a new user, fetching the user again with usermanager for testing, and then using the method AddLoginAsync with the recently fetched user gives the error ConcurrencyFailure, Optimistic concurrency failure, object has been modified. When fetching the user the "ConcurrencyStamp" has the correct etag, but after the "AddLoginAsync" I can see the user object has an invalid etag, the ConcurrencyStamp is a GUID. I have followed the documentation and added this to the IdentityUser model

问题 I am trying to build a structure using repository pattern in entity framework core. I have an generic interface and a service for general operations. They simply do CRUD transactions. My interface: public interface IGeneralService<TEntity> where TEntity : class { void Delete(TEntity entityToDelete); void Delete(object id); IEnumerable<TEntity> Get( Expression<Func<TEntity, bool>> filter = null, Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null, string includeProperties = ""

问题 I am trying to build a structure using repository pattern in entity framework core. I have an generic interface and a service for general operations. They simply do CRUD transactions. My interface: public interface IGeneralService<TEntity> where TEntity : class { void Delete(TEntity entityToDelete); void Delete(object id); IEnumerable<TEntity> Get( Expression<Func<TEntity, bool>> filter = null, Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null, string includeProperties = ""

问题 After migrating from .NET Core 2.x to .NET Core 5.0, we are facing this problem. Error: (Added as a CODE for better readability) The LINQ expression 'OUTER APPLY Projection Mapping: ( SELECT e0.Id, e0.FirstName, e0.MiddleName, e0.LastName FROM Employees AS e0 WHERE (((e0.Status != 4) && EXISTS ( Projection Mapping: SELECT 1 FROM FunctionRoles AS f0 WHERE t.Id == f0.SchoolId)) && (e0.FunctionRoleId == (Projection Mapping: EmptyProjectionMember -> 0 SELECT TOP(1) f1.Id FROM FunctionRoles AS f1

问题 I have this Project class: public class Project { public int Id { get; set; } public int? ParentId { get; set; } public List<Project> ChildProjects { get; set; } // more properties } This is my attempt to load all descendants of any given project: private async Task<List<Project>> LoadDescendantsOf(Project project) { project.ChildProjects = await db.Projects .Where(p => p.ParentId == project.Id) .ToListAsync(); foreach (Project childProject in project.ChildProjects) { yield return

问题 I have an ASP.NET Core 5 project (migrated from ASP.NET Core 3.1). The project uses EF Core. EF Core 5 has built-in support for Many-to-Many. The main reason I first migrated from 3.1 to 5.0. Now my project has a One-to-Many relationship, which I want to convert to a Many-to-Many. Is such a relationship migration possible? Current code: public class File { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] [Key] public int Id { get; set; } [DatabaseGenerated(DatabaseGeneratedOption