插入else更新

public void InsertUpdateData()
{
//Here TestEntities is the class which is given from "Save entity connection setting in web.config"
TestEntities context = new TestEntities();

var query = from data in context.Employee
            orderby data.name
            select data;

foreach (Employee details in query)
{
    if (details.id == 1)
    {
        //Assign the new values to name whose id is 1
        details.name = "Sanjay";
        details. Surname="Desai";
        details.address=" Desiwadi";
    }
    else if(query==null)
    {
        details.name="Sharad";
        details.surname=" Chougale ";
        details.address=" Gargoti";
    }
}

//Save the changes back to database.
context.SaveChanges();
}

神奇的是在调用SaveChanges()时发生的，这取决于当前的EntityState。如果实体有一个EntityState。如果它有一个EntityState，那么它将被添加到数据库中。修改后，将在数据库中更新。所以你可以实现InsertOrUpdate()方法，如下所示:

public void InsertOrUpdate(Blog blog) 
{ 
    using (var context = new BloggingContext()) 
    { 
        context.Entry(blog).State = blog.BlogId == 0 ? 
                                   EntityState.Added : 
                                   EntityState.Modified; 

        context.SaveChanges(); 
    } 
}

更多关于EntityState的信息

如果你不能检查Id = 0来确定它是否是一个新实体，请检查Ladislav Mrnka的答案。

Ladislav的答案很接近，但我不得不做了一些修改，以使其在EF6(数据库优先)中工作。我用我的AddOrUpdate方法扩展了我的数据上下文，到目前为止，这似乎与分离的对象工作得很好:

using System.Data.Entity;

[....]

public partial class MyDBEntities {

  public void AddOrUpdate(MyDBEntities ctx, DbSet set, Object obj, long ID) {
      if (ID != 0) {
          set.Attach(obj);
          ctx.Entry(obj).State = EntityState.Modified;
      }
      else {
          set.Add(obj);
      }
  }
[....]

使用Any检查现有行。

public static void insertOrUpdateCustomer(Customer customer)
{
    using (var db = getDb())
    {

        db.Entry(customer).State = !db.Customer.Any(f => f.CustomerId == customer.CustomerId) ? EntityState.Added : EntityState.Modified;
        db.SaveChanges();

    }

}

从实体框架4.3开始，在命名空间System.Data.Entity.Migrations中有一个AddOrUpdate方法:

public static void AddOrUpdate<TEntity>(
    this IDbSet<TEntity> set,
    params TEntity[] entities
)
where TEntity : class

医生说:

在调用SaveChanges时按键添加或更新实体。等效 到数据库术语中的“upsert”操作。此方法可以是 在使用迁移播种数据时很有用。

为了回答@Smashing1978的评论，我将从@Colin提供的链接中粘贴相关部分

The job of AddOrUpdate is to ensure that you don’t create duplicates when you seed data during development. First, it will execute a query in your database looking for a record where whatever you supplied as a key (first parameter) matches the mapped column value (or values) supplied in the AddOrUpdate. So this is a little loosey-goosey for matching but perfectly fine for seeding design time data. More importantly, if a match is found then the update will update all and null out any that weren’t in your AddOrUpdate.

也就是说，我有一种情况，我从外部服务中提取数据，并通过主键插入或更新现有值(并且我的消费者本地数据是只读的)-在生产中使用AddOrUpdate已经超过6个月了，到目前为止没有问题。

纠正

public static void InsertOrUpdateRange<T, T2>(this T entity, List<T2> updateEntity) 
        where T : class
        where T2 : class
        {
            foreach(var e in updateEntity)
            {
                context.Set<T2>().InsertOrUpdate(e);
            }
        }


        public static void InsertOrUpdate<T, T2>(this T entity, T2 updateEntity) 
        where T : class
        where T2 : class
        {
            if (context.Entry(updateEntity).State == EntityState.Detached)
            {
                if (context.Set<T2>().Any(t => t == updateEntity))
                {
                   context.Set<T2>().Update(updateEntity); 
                }
                else
                {
                    context.Set<T2>().Add(updateEntity);
                }

            }
            context.SaveChanges();
        }