ef-code-first

问题 Is it possible to control eager loading of child objects. If I had a parent class that has 20,000 child objects and I only wanted to retrieve a subset of those child objects is it possible? How would I write the query to do that if it is? For Example: I have an Entity called Book which has a number of related Reviews: public class Book { public int BookId { get; set; } public string BookName { get; set; } public ICollection<Review> Reviews { get; set; } } public class Review { public int

问题 I'm using EF6 code first with .NET4(I should deliver the project on win xp so I couldn't configure it with .NET4.5) in a win Form project. I have a BaseEntity class that all other entities inherited from it: public abstract class BaseEntity { public int Id {get; set;} public int X {get; set;} public int Y {get; set;} } public class Calendar:BaseEntity { // properties } How could I Ignore X,Y properties in my all entities without writing following code for each entity? modelBuilder.Entity

问题 im new to mvc and im trying out some stuff with code first. im currently having problems with my dbase, whenever i build my application the build finishes successfully but i dont see my dbase get created whenever i check my local server. was wondering if there's something im missing on my connection string. <connectionStrings> <add name="mydbase" connectionString="Data Source=localhost;Database=mydbase;Trusted_Connection=yes;" providerName="System.Data.SqlClient" /> </connectionStrings> or

问题 Suppose I have code like: public void TestWhenSqlFires() { var db = new Db(); // EF DbContext var items = db.SimpleObjects; // SimpleObject implements interface IId var byId = WhereId(items, 1); var array = byId.ToArray(); } protected IEnumerable<IId> WhereId(IEnumerable<IId> items, int id) { return items.Where(i => i.Id == id); } At what line in TestWhenSqlFires() will SQL actually be run against the database? (This is a question that spun off from comments on this answer) 回答1: One way to

问题 The problem Query BaseClass and Include information from derived types. For example: Base class Offer has two types one with a Card only ( CardOffer ) and with Multiple Cards ( CarouselOffer ). Question: How to query the BaseClass and Include the information from the derived types CardOffer and CarouselOffer? In the manner shown below: _dbContext.Offers.Include(...).ToList(); Currently I solved this by querying each inherited type var cards = await _dbContext.CardOffers .Include(c => c.Card)

问题 I have problems mapping a overrided property from a POCO object to database using TPH in Code First. My code is similar to these classes: public abstract class Vehicle { public int ID { get; set; } public abstract NumberOfWheels { get; set;} } public class Motorbike: Vehicle { public override NumberOfWheels { get; set; } } When I try to save the Motorbike class to Database I get the next message The property 'NumberOfWheels' is not a declared property on type 'Motorbike'. Verify that the

问题 I am still new in EF code first, so please be lenient with me. I have these entity classes: public class User { public int UserId { get; set; } public string UserName { get; set; } public string EmailAddress { get; set; } public string Password { get; set; } public virtual ICollection<Task> Tasks { get; set; } public virtual ICollection<Task> TaskAssignees { get; set; } public User() { Tasks = new List<Task>(); } } public class Task { public int TaskId { get; set; } public string Name { get;

问题 I am working on asp.net mvc with EF code first model. I am trying to apply migrations using EF code first to my project. I am using MySql database. currently i am using EF 4.3.1 version and mysql connector/.net of 6.6.4.0 version. I am successfully add migrations to my project that means i execute series of commands that gave no errors for me. I have followed these steps, PM> Enable-Migrations PM> Add-Migration InitialMigration PM> update-database -verbose these steps create Migration folder

问题 After the first execution of the update-database command to populate the database with seed data: Found that all int Id columns started with zero (0) rather than the expected one (1). Added the following 2 lines of code for each entity/table to the top of the Seed method in Configuration.cs: [Note: Because of the foreign key constraints, I deleted all rows in descendent tables, and then worked my way up the ancestral chain.] context.Database.ExecuteSqlCommand("delete from Widgets"); context

问题 I have below entity with a calculated/computed column: public EntityA { [Key(), Required] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Id { get; set; } ..... [DatabaseGenerated(DatabaseGeneratedOption.Computed)] public virtual string RefId { get { return this.Id.ToString().PadLeft(7, '0'); } private set { } } } RefId is a computed column that depends on the Id value. After performing commit changes to database with SaveChanges I can check that Id and RefId have been set