Question

我正在向数据库编写许多（20多个）父子数据集，并且EF要求我在每个集合之间保存更改，否则它会抱怨无法找出主键。是否可以将数据刷新到SQL Server，以便EF可以从身份中获取主键，并在写入所有更改结束时发送SaveChanges？

foreach (var itemCount in itemCounts)
{
    var addItemTracking = new ItemTracking
    {
        availabilityStatusID = availabilityStatusId,
        itemBatchId = itemCount.ItemBatchId,
        locationID = locationId,
        serialNumber = serialNumber,
        trackingQuantityOnHand = itemCount.CycleQuantity
    };
    _context.ItemTrackings.Add(addItemTracking);
    _context.SaveChanges();
    var addInventoryTransaction = new InventoryTransaction
    {
        activityHistoryID = newInventoryTransaction.activityHistoryID,
        itemTrackingID = addItemTracking.ItemTrackingID,
        personID = newInventoryTransaction.personID,
        usageTransactionTypeId = newInventoryTransaction.usageTransactionTypeId,
        transactionDate = newInventoryTransaction.transactionDate,
        usageQuantity = usageMultiplier * itemCount.CycleQuantity
    };
    _context.InventoryTransactions.Add(addInventoryTransaction);
    _context.SaveChanges();
}

我想在大循环结束时只做一次我的SaveChanges。

Answer 1

如果您使用对象引用新创建的对象而不是ID，则不需要每次都保存更改：

var addItemTracking = new ItemTracking
{
    ...
}
_context.ItemTrackings.Add(addItemTracking);
var addInventoryTransaction = new InventoryTransaction
{
    itemTracking = addItemTracking,
    ...
};
_context.InventoryTransactions.Add(addInventoryTransaction);
...
_context.SaveChanges();

Answer 2

因为它们都是新项而不是

itemTrackingID = addItemTracking.ItemTrackingID,

你可以选择

addItemTracking.InventoryTransaction = addInventoryTransaction;

（或任何相关的导航属性）并将_context.SaveChanges（）完全拉出循环。当一切都是新的时，Entity Framework非常擅长插入对象图。保存包含新项目和现有项目的对象图表时，设置关联的ID始终更安全。

Answer 3

怎么样：

var trackingItems = itemCounts
    .Select(i => new ItemTracking
        {
            availabilityStatusID = availabilityStatusId,
            itemBatchId = i.ItemBatchId,
            locationID = locationId,
            serialNumber = serialNumber,
            trackingQuantityOnHand = i.CycleQuantity
        });
_context.ItemTrackings.AddRange(trackingItems);
_context.SaveChanges();

var inventoryTransactions = trackingItems
    .Select(t => new InventoryTransaction
        {
            activityHistoryID = newInventoryTransaction.activityHistoryID,
            itemTrackingID = t.ItemTrackingID,
            personID = newInventoryTransaction.personID,
            usageTransactionTypeId = newInventoryTransaction.usageTransactionTypeId,
            transactionDate = newInventoryTransaction.transactionDate,
            usageQuantity = usageMultiplier * t.trackingQuantityOnHand
        });
_context.InventoryTransactions.AddRange(inventoryTransactions);
_context.SaveChanges();

但是我已经有很长一段时间没用EF了，上面的代码是用记事本写的，所以我不能保证它

实体框架可以使用单个SaveChanges（）添加许多相关实体吗？

3 个答案: