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();
}

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。

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();

    }

}

如果你正在使用附加对象(从上下文的同一个实例加载的对象)，你可以简单地使用:

if (context.ObjectStateManager.GetObjectStateEntry(myEntity).State == EntityState.Detached)
{
    context.MyEntities.AddObject(myEntity);
}

// Attached object tracks modifications automatically

context.SaveChanges();

如果你可以使用任何关于对象键的知识，你可以使用这样的东西:

if (myEntity.Id != 0)
{
    context.MyEntities.Attach(myEntity);
    context.ObjectStateManager.ChangeObjectState(myEntity, EntityState.Modified);
}
else
{
    context.MyEntities.AddObject(myEntity);
}

context.SaveChanges();

如果你不能通过Id判断对象是否存在，你必须执行查找查询:

var id = myEntity.Id;
if (context.MyEntities.Any(e => e.Id == id))
{
    context.MyEntities.Attach(myEntity);
    context.ObjectStateManager.ChangeObjectState(myEntity, EntityState.Modified);
}
else
{
    context.MyEntities.AddObject(myEntity);
}

context.SaveChanges();

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();
        }

试试这个算法

public void InsertOrUpdate(Item item) 
{ 
    using (var context = new ItemContext()) 
    { 
       var existedItem = context.Items.Where(x => x.Id==item.Id).FirstOrDefault();

       if(existedItem != null)
       {
          context.Entry(existedItem).CurrentValues.SetValues(item);
          
              //or only if you want to update some special properties
                existedItem.Prop1=item.Prop1;
                existedItem.Prop2=item.Prop2
                context.Entry(existedItem).State =EntityState.Modified;
              //-----------

       } 
       else 
       { 
        context.Items.Add(item);
       }

    context.SaveChanges();
   }
}