面试题与答案

Entity Framework (EF) is an object-relational mapping (ORM) framework that enables developers to work with relational data using domain-specific objects.

DbContext is a class in EF that represents a session with the database, allowing you to query and save data.

You can disable Lazy Loading by setting the LazyLoadingEnabled property of the DbContext to false.

The Include method is used to specify related entities that should be loaded along with the main entity. For example, context.Orders.Include(o => o.Customer).ToList();

The AsNoTracking method is used to disable change tracking for a specific query, which can improve performance when you only need to read data.

The [Table] attribute is used to specify the table name for an entity when it does not match the default convention.

Example:

[Table("MyCustomTableName")] public class MyEntity { /* properties */ }

The [Key] attribute is used to specify the primary key property of an entity when it does not match the default convention.

Example:

[Key] public int MyCustomId { get; set; }

The [NotMapped] attribute is used to specify that a property should not be mapped to a column in the database.

Example:

[NotMapped] public string CalculatedProperty { get { /* calculation logic */ } }

The DbSet.Find method is used to retrieve an entity from the database by its primary key value.

Example:

var entity = context.MyEntities.Find(1);

The [MaxLength] attribute is used to specify the maximum length of a string or binary property when creating the database schema.

Example:

[MaxLength(50)] public string Name { get; set; }

The ToListAsync method is used to asynchronously execute a query and return the result as a List.

Example:

var result = await context.Entities.ToListAsync();

The [Required] attribute is used to specify that a property is required and must have a non-null value when saving to the database.

Example:

[Required] public string Name { get; set; }

The [StringLength] attribute is used to specify the maximum length of a string property when creating the database schema.

Example:

[StringLength(100)] public string Description { get; set; }

The Add method is used to add a new entity to the context, marking it as Added, and inserting it into the database when SaveChanges is called.

Example:

context.Entities.Add(newEntity);

The Remove method is used to mark an entity as Deleted in the context, and the entity will be deleted from the database when SaveChanges is called.

Example:

context.Entities.Remove(entityToDelete);

The AsQueryable method is used to convert an IEnumerable to IQueryable, enabling the use of LINQ expressions to query a collection.

Example:

var queryable = list.AsQueryable();

The Set method is used to get a DbSet for a given entity type, allowing you to perform database operations on that entity type.

Example:

var set = context.Set();

The FindAsync method is used to asynchronously retrieve an entity from the database by its primary key value.

Example:

var entity = await context.MyEntities.FindAsync(1);