entity-framework - 关于 System.Data.EntityState.Add 和 DbSet.Add 之间差异(如果有)的令人困惑的文章和文档

Question

我正在使用 EF 5 开发 C# ASP.NET MVC 5 Web 应用程序。使用 EF 映射我的数据库表会生成 DbContext类和 .edmx文件。今天，我正在阅读a great article about creating generic DAL classes ，但我停在了以下句子上:

Note that using the Entry method to change the state of an entity will only affect the actual entity that you pass in to the method. It won’t cascade through a graph and set the state of all related objects, unlike the DbSet.Add method.

这与这些问题中提到的内容相矛盾:

http://forums.asp.net/p/2015170/5803192.aspx

http://forums.asp.net/p/2060606/5943259.aspx

Difference between DbSet.Add(entity) and entity.State = EntityState.Added

What is the difference between IDbSet.Add and DbEntityEntry.State = EntityState.Added?

在以上所有问题的回答中，所有用户都提到使用 System.Data.EntityState.Added与使用 DbSet.Add 完全相同.但是我首先提到的文章指出使用 System.Data.EntityState.Added不会通过图形级联。

根据我的测试，我得出结论，使用 System.Data.EntityState.Added将级联通过与 DBset.Add 相同的图形案件。是文章错了，还是我的测试和问答？

Answer 1

这些方法是相同的，您可以通过常规测试进行验证，或者，如果您想完全确定 - 通过对 EF 6 代码的一些探索。

DbSet.Add方法 ( http://entityframework.codeplex.com/SourceControl/latest#src/EntityFramework/DbSet.cs )

public virtual TEntity Add(TEntity entity)
{
    Check.NotNull<TEntity>(entity, "entity");
    this.GetInternalSetWithCheck("Add").Add((object) entity);
    return entity;
}

这叫 InternalSet<T>.Add(object)方法。

DbEntityEntry<T>.State属性(property) ( http://entityframework.codeplex.com/SourceControl/latest#src/EntityFramework/Infrastructure/DbEntityEntry.cs )

public EntityState State
{
    get { return _internalEntityEntry.State; }
    set { _internalEntityEntry.State = value; }
}

哪里 _internalEntityEntry是 InternalEntityEntry类型。
InternalEntityEntry.State属性(property) ( http://entityframework.codeplex.com/SourceControl/latest#src/EntityFramework/Internal/EntityEntries/InternalEntityEntry.cs )

    public virtual EntityState State
    {
        get { return IsDetached ? EntityState.Detached : _stateEntry.State; }
        set
        {
            if (!IsDetached)
            {
                if (_stateEntry.State == EntityState.Modified
                    && value == EntityState.Unchanged)
                {
                    // Special case modified to unchanged to be "reject changes" even
                    // ChangeState will do "accept changes".  This keeps the behavior consistent with
                    // setting modified to false at the property level (once that is supported).
                    CurrentValues.SetValues(OriginalValues);
                }
                _stateEntry.ChangeState(value);
            }
            else
            {
                switch (value)
                {
                    case EntityState.Added:
                        _internalContext.Set(_entityType).InternalSet.Add(_entity);
                        break;
                    case EntityState.Unchanged:
                        _internalContext.Set(_entityType).InternalSet.Attach(_entity);
                        break;
                    case EntityState.Modified:
                    case EntityState.Deleted:
                        _internalContext.Set(_entityType).InternalSet.Attach(_entity);
                        _stateEntry = _internalContext.GetStateEntry(_entity);
                        Debug.Assert(_stateEntry != null, "_stateEntry should not be null after Attach.");
                        _stateEntry.ChangeState(value);
                        break;
                }
            }
        }
    }

您会看到，如果实体已分离(您的情况)并且状态已添加 - 相同 InternalSet<T>.Add(object)叫做。

至于通过测试验证:

using (var ctx = new TestDBEntities()) {
    // just some entity, details does not matter
    var code = new Code();
    // another entity
    var error = new Error();
    // Code has a collection of Errors
    code.Errors.Add(error);
    var codeEntry = ctx.Entry(code);
    // modify code entry and mark as added
    codeEntry.State = EntityState.Added;
    // note we did not do anything with Error
    var errorEntry = ctx.Entry(error);
    // but it is marked as Added too, because when marking Code as Added -
    // navigation properties were also explored and attached, just like when
    // you do DbSet.Add
    Debug.Assert(errorEntry.State == EntityState.Added);                
}