Question

我遇到了简单的foreach问题。我试图从数据库中获取数据到我的列表。

IList<DeliveredTaskModel> deliveredTaskModel = new List<DeliveredTaskModel>();
// lines of code 

if (materialUsed.Count > 0)
{
    foreach (var material in materialUsed)
    {
        var deliveryModel = new DeliveredTaskModel();
        deliveryModel.Info = materialUsed[0].SubPartCode;
        deliveryModel.Description = materialUsed[0].Description;
        deliveryModel.Qty = materialUsed[0].Qty;
        deliveredTaskModel.Add(deliveryModel);
    }
}

当我在foreach上设置断点时。我可以看到它在materialUsed中有4个不同的项目。但是，当我执行此操作时，它只是将相同项目的4倍添加到网格中。

我认为它会不断添加相同的项目，但为什么呢？有人可以解释一下吗？

Answer 1

您始终通过索引零访问。要纠正的选项：

如果您使用foreach，请使用：

foreach (var material in materialUsed)
{
    var deliveryModel = new DeliveredTaskModel();
    deliveryModel.Info = material.SubPartCode;
    deliveryModel.Description = material.Description;
    deliveryModel.Qty = material.Qty;
    deliveredTaskModel.Add(deliveryModel);
}

如果您使用索引器更改为for-loop：

for(int i = 0; i < materialUsed.Count, i++)
{
    var deliveryModel = new DeliveredTaskModel();
    deliveryModel.Info = materialUsed[i].SubPartCode;
    deliveryModel.Description = materialUsed[i].Description;
    deliveryModel.Qty = materialUsed[i].Qty;
    deliveredTaskModel.Add(deliveryModel);
}

然后用户属性初始化程序会更好：

foreach (var material in materialUsed)
{
    deliveredTaskModel.Add(new DeliveredTaskModel
    {
        Info = material.SubPartCode,
        Description = material.Description,
        Qty = material.Qty
    });
}

然后使用linq，您可以使用.Select

来实现它

var deliveredTaskModel = materialUsed.Select(model => new DeliveredTaskModel
    {
        Info = material.SubPartCode,
        Description = material.Description,
        Qty = material.Qty
    }).ToList();

我建议你选择最后一个选项：）

最后一条评论 - 你的if语句(materialUsed.Count > 0)是多余的，因为如果集合为空，它将不会进入循环

Answer 2

您在循环中引用相同的固定索引：

deliveryModel.Info = materialUsed[0].SubPartCode;

您需要使用循环变量：

deliveryModel.Info = material.SubPartCode;

Answer 3

您应该在foreach循环的每次迭代中使用当前项而不是引用列表。试试这个：

IList<DeliveredTaskModel> deliveredTaskModel = new List<DeliveredTaskModel>();

        if (materialUsed.Count > 0)
        {
            foreach (var material in materialUsed)
            {
                var deliveryModel = new DeliveredTaskModel();
                deliveryModel.Info = material .SubPartCode;
                deliveryModel.Description = material .Description;
                deliveryModel.Qty = material .Qty;
                deliveredTaskModel.Add(deliveryModel);
            }
        }

Answer 4

$collection = Mage::getModel('catalog/product')->getCollection()
    ->addStoreFilter($this->_getStoreId($store))
    ->addAttributeToSelect('name');
if($limit) {
    $collection->setOrder('updated_at', 'ASC');
    $collection->setPageSize($limit);
}
/** @var $apiHelper Mage_Api_Helper_Data */
$apiHelper = Mage::helper('api');
$filters = $apiHelper->parseFilters($filters, $this->_filtersMap);
try {
    foreach ($filters as $field => $value) {
        $collection->addFieldToFilter($field, $value);
    }
} catch (Mage_Core_Exception $e) {
    $this->_fault('filters_invalid', $e->getMessage());
}
$result = array();
foreach ($collection as $product) {
    $result[] = array(
        'product_id' => $product->getId(),
        'sku'        => $product->getSku(),
        'name'       => $product->getName(),
        'set'        => $product->getAttributeSetId(),
        'type'       => $product->getTypeId(),
        'category_ids' => $product->getCategoryIds(),
        'website_ids'  => $product->getWebsiteIds(),
        'updated_at'  => $product->getUpdatedAt(),
        'created_at'  => $product->getCreatedAt()
    );
}
return $result;

materialUsed [0]是你列表中的第一项，无论你在第一项列表中有多少项，你都应该把当前项目当作“材料”

C＃Foreach继续将相同的项目添加到列表中

4 个答案: