Question

我需要使用XML文件创建缓存。这是我将要使用的方法。我希望此方法基于key-product_name返回id。所以我希望它以编程方式一次创建一个缓存，然后只有在找不到密钥时才创建一个[缓存中的新条目]。如果一切看起来都没问题，问题在于获得产品的ID。请指教。我已经包含了代码和xml文件。

public static string getProductId(string product_name)
    public static string getTechId(string fieldName)
    {
        Cache cache = HttpContext.Current.Cache;  //neeed to change this.
        string cacheNameEpm = product_name + "PrdName";

        if (cache[cacheNameEpm] == null)
        {
            XPathDocument doc = new XPathDocument(HttpContext.Current.Request.MapPath("inc/xml/prd.xml"));
            XPathNavigator navigator = doc.CreateNavigator();
            string selectName = "/Products/Product/ProductName";
            XPathNodeIterator nodes = navigator.Select(selectName);

            while (nodes.MoveNext())
            {
                switch (nodes.Current.Name)
                {
                    case "ProductName":
                        cacheNameEpm = nodes.Current.Value + "PrdName";
                        navigator.Select("/Products/Product/ProductId");
                        navigator.MoveToNext();
                        if (nodes.Current.Name == "ProductId")
                        {
                            id = navigator.Value;
                        }
                        cache.Add(cacheNameEpm, id, null, DateTime.Now + new TimeSpan(4, 0, 0), System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.Default, null);
                        break;
                }
            }
        }

        return cache[cacheNameEpm] as string;
    }

这是xml文件：

<Products>
    <Product>
        <ProductName>PDPArch</ProductName>
        <ProductId>57947</ProductId>
    </Product>
    <Product>
        <ProductName>TYFTType</ProductName>
        <ProductId>94384</ProductId>
    </Product>
</Products>

Answer 1

要获取"TYFTType"的产品ID，您需要此XPath表达式：

/Products/Product[ProductName = 'TYFTType']/ProductId

那么（未经测试，但你得到了想法）的事情是什么：

public static string getProductId(string product_name)
{
  Cache cache = HttpContext.Current.Cache;

  string cacheNameEpm = product_name + "PrdName";
  if (cache[cacheNameEpm] == null)
  {
    // let's cache the navigator itself as well
    string cacheNameNav = "prd.xml_Navigator";
    XPathNavigator navigator = cache[cacheNameNav] as XPathNavigator;

    if (navigator == null)
    {
      XPathDocument doc = new XPathDocument(
        HttpContext.Current.Request.MapPath("inc/xml/prd.xml")
      );
      navigator = doc.CreateNavigator();
      cache.Add(
        cacheNameNav,
        navigator,
        null,
        DateTime.Now + new TimeSpan(4, 0, 0),
        Cache.NoSlidingExpiration,
        CacheItemPriority.Default,
        null
      );
    }

    string xpath = String.Format(
      "/Products/Product[ProductName = '{0}']/ProductId", product_name
    );

    XPathNavigator product_id = navigator.SelectSingleNode(xpath);

    if (product_id.IsNode)
    {
      cache.Add(
        cacheNameEpm,
        product_id.Value,
        null,
        DateTime.Now + new TimeSpan(4, 0, 0),
        Cache.NoSlidingExpiration,
        CacheItemPriority.Default,
        null
      );
    }
  }

  return cache[cacheNameEpm] as string;
}

以上有两个小问题：

它不会记住不存在的产品名称。
产品名称不得包含单引号，否则XPath表达式将中断。您应该添加一个检查此条件。

需要获得兄弟姐妹的价值

1 个答案: