entity-framework

问题 I have some similar entities and I want to create a generic abstract class for CRUD operations for them, but I don't know how can access to entities in generic class. For example: public abstract class HeaderRepository<T> { public HeaderRepository() { } public virtual byte[] Insert(T item) { using (MyEntities context = new MyEntities()) { context.***** <-- What I should write to add an object to entity T } } } I hope I've got it. 回答1: You need to set your DB set. It would be better to have a

问题 My persons class: public class User { public int Id { get; private set; } public string Isim { get; set; } public string Soyad { get; set; } public User(string isim, string soyad) { Isim = isim; Soyad = soyad; } } My UserBusiness class: public sealed class UserBusiness { JuqueryDbEntities entity = new JuqueryDbEntities(); private static volatile UserBusiness instance; private static readonly object syncRoot = new Object(); private UserBusiness() { } public static UserBusiness Instance { get {

问题 get-migrations shows full list of all my migrations but only half of them is in the _MigrationHistory and the database has changes from these half of them. No errors , all migrations applied successfully. issue comes while applying migrations having int to float changes were i had to manually add Sql("ALTER TABLE xxx DROP CONSTRAINT DF__TBL_OPRTN__OPRTN__6497E884"); . Is there any possible reason for these kind of behaviour from ef , any way to debug this? thanks 来源： https://stackoverflow.com

问题 I'm trying to add an entity to my database with the following code: public void StoreElectronicSignatureType(ElectronicSignatureTypeModel model) { [...] ElectronicSignatureType electronicSignatureType = new ElectronicSignatureType(); Entity entity = GetEntity("Test"); electronicSignatureType.Entity = entity; Add(electronicSignatureType); public void Add(object entity) { DbContext.Entry(entity).State = System.Data.EntityState.Added; //DbContext.Set(entity.GetType()).Add (entity); DbContext

问题 I have some records which I fetch from database (normally about 100-200). I also need to get the corresponding Place for every record and fill in the Description of the Place in the record. I would normally do that in my .Select function but I need to check if Place isn't null before trying to take the Description . My code goes like this: var places = db.Places.Where(p => p.Active && p.CustomerID == cust_ID).ToArray(); foreach (var result in query) result.Description = places.Where(Place.Q

问题 When var codeFirstRepositor = new Donors(); var list = codeFirstRepositor.CampaignReps.Select(c => c).ToList(); When I put a breakpoint inside the CampaignRep class constructor it is not called at all - the exception seems to occur before object instantiation Context public class Donors : DbContext { public Donors() { // Needed for WCF serialization to work Configuration.ProxyCreationEnabled = false; } public DbSet<CampaignRep> CampaignReps { get; set; } } EntitySqlException 'CampaignsReps'

问题 I made a view so the back hand of my website is more coherent. Then i tried to map it to my entity schema. I had the message : No primary key defined, could not deduce a primary key, table excluded So i made one ! I made sure it was something unique by combining 3 columns that cannot be identical when combined. And i called that new column "id". Entity dosen't seems to agree with the unique aspect of my "id" because the error message wont go away and i can't import my view... 回答1: Well, i had

问题 I'm used to using code first where I can do: db.Users.Attach(user); db.Entry(user).Property(propertyName).IsModified = true; How do I do this with a DataModel approach? I do not have the Entry method on my datacontext. 回答1: Use: context.Users.Attach(user); ObjectStateEntry entry = context.ObjectStateManager.GetObjectStateEntry(user); entry.SetModifiedProperty(propertyName); 来源： https://stackoverflow.com/questions/6947950/entity-framework-4-update-specific-properties

问题 Yesterday I asked this question about changing the name of the __Migration History table generated by Entity Framework when using a Code First approach. The provided link was helpful in saying how to do what we want (and by "want" I mean what we're being forced into by our DBAs), however also left a somewhat non-specific and dire-sounding warning that says, Words of precaution Changing the migration history table is powerful but you need to be careful to not overdo it. EF runtime currently

问题 I have a metadata class with some custom properties for easier data access. One problem that I have run across though, is that when I try to use this property in LINQ statements I get this error. The specified type member 'CrewCodesStr' is not supported in LINQ to Entities. I know why I get it, I'm wondering if there is another way to do this to allow the property to be used in LINQ statements. Here is the property: public string CrewCodesStr { get { return string.Join(", ", CrewCodesList); }