c# - 通用插入或更新方法

Question

我有一个更新或插入和实体的通用方法。我不明白这里 if 语句的目的。该评论告诉我它的用途，但我不清楚。

为什么要根据 System.Data.Entity.DynamicProxies 检查命名空间。我以为通过实体框架检索到的所有实体都在这个命名空间下？为什么我们要检查基类型是否为空？

public virtual T InsertOrUpdate(T e)
{
DbSet<T> dbSet = Context.Set<T>();

DbEntityEntry<T> entry;
if (e.GetType().BaseType != null 
    && e.GetType().Namespace == "System.Data.Entity.DynamicProxies")
{
    //The entity being added is already a proxy type that supports lazy 
    //loading - just get the context entry
    entry = Context.Entry(e);
}
else
{
    //The entity being added has been created using the "new" operator. 
    //Generate a proxy type to support lazy loading  and attach it
    T instance = dbSet.Create();
    instance.ID = e.ID;
    entry = Context.Entry(instance);
    dbSet.Attach(instance);

    //and set it's values to those of the entity
    entry.CurrentValues.SetValues(e);
    e = instance;
}

entry.State = e.ID == default(int) ?
                        EntityState.Added :
                        EntityState.Modified;

    return e;
}

标签： c#.netentity-framework