entity-framework

问题 I have some .NET Core code that does some bulk loading of the DB with random sample data. I'm getting 20 inserts/second on localhost, and looking to improve my performance. I'm doing the basic stuff like calling _dbContext.SaveChanges() only once, etc. A number of posts like this indicate gains can be had by manipulating properties on the DbContext's Configuration, such as Configuration.AutoDetectChangesEnabled and Configuration.ValidateOnSaveEnabled . My .NET Core MVC app's DbContext is a

问题 I've got a class User which has an attribute Name that must be unique. So far I've investigated 3 ways of checking this: Annotations [StringLength(100)] [Index(IsUnique = true)] public string Name { get; set; } Problem is, by trying to insert a user with a repeated name it throws this ex: as you can see, I would have to navigate into the inner exceptions (which I don´t know if it is possible, but I assume it is) and the last inner exception´s message is not user friendly at all. Fluent Api

问题 I have set up a self referential entity using EF Core which looks like this: Entity public class DetailType { public int DetailTypeId { get; set; } public string Name { get; set; } public int? ParentTypeId { get; set; } public DetailType ParentType { get; set; } public IEnumerable<DetailType> ChildTypes { get; set; } } Binding modelBuilder.Entity<DetailType>() .ToTable("detailtype") .HasOne(x => x.ParentType) .WithMany(x => x.ChildTypes) .HasForeignKey(x => x.ParentTypeId); I am retrieving

问题 For a business application, I am providing a base entity model. Thereafter the end user should be able to extend the model for his specific needs. For the base model I want to use database-first approach. But I don't know how to accommodate for allowing user to extend it. One part is to provide a UI for entity model editing and the other is to reflect the changes in the model and database thereafter. Please offer suggestions. EDIT : - Once the entity model is edited and saved, all EF

问题 For a business application, I am providing a base entity model. Thereafter the end user should be able to extend the model for his specific needs. For the base model I want to use database-first approach. But I don't know how to accommodate for allowing user to extend it. One part is to provide a UI for entity model editing and the other is to reflect the changes in the model and database thereafter. Please offer suggestions. EDIT : - Once the entity model is edited and saved, all EF

问题 I am trying to use stored procedures in Entity Framework Core. When executing a stored procedure, I am passing two input parameters and one output parameter. I keep getting this error: The SqlParameterCollection only accepts non-null SqlParameter type objects, not SqlParameter objects. This is my code: public string InsertCardsData(DateTime RecordingStartDate, DateTime RecordingEndDate) { try { // DateTime DRecEndDate = Convert.ToDateTime(RecordingEndDate); DateTime DRecEndDate =

问题 In our application, we have an api which will store some data to a database. We are using Entity Framework Core 3.1.1 . After this entity has been stored, a message is posted to Azure Servicebus and a consumer will read this message a store the message to another table in the same DbContext . As far as I understand, a LifetimeScope is defined per request to the api. The LifetimeScope will start when the api request hits the ApiController and finishes when the endpoint is done processing the

问题 I have a table called Article: -Id -Title -Content -Tags (This is a comma seperated list of tags e.g. 'Sports,Italy,Ferrari') Using entity framework i want to be able to find all articles that have certain tags. List<Article> GetArticles(List<String> tags) { //do an entity framework query here to find all articles which have the tags specified } The returned entries should contain all the tags specified. e.g. If the input to the function was 'car','blue', then all entries with these at least

问题 How do I override the serial/sequence in an ID field when adding records with Entity Framework on a PostgreSQL database? The serial/sequence auto incrementing ID works fine, when adding records, but I need to write a migration script where the old records I migrate must maintain their old ID's. It works fine if I just shoot an INSERT query directly to the server, but when doing with with Entity Framework, they just start from 1, 2, 3 etc. 回答1: You should to reset sequence in the database

问题 I use Visual Studio 2013 and need to use Entity Framework code first approach in a project. I used NuGet Manager to install EF v6.1 into my project. But I can't create an empty code first model or even a code first model from database although there are two other choices (DB first and Model first). How I can add Entity Framework code first feature to my project? 回答1: Here is a beginners tutorial for using entity framework code first: An Absolute Beginner's Tutorial for understanding Entity