Need to get the sibling value - xpath

Question

I need to create a cache using an XML file. Here's the method that I will be using. I want this method to return the id based on the key-product_name. So I want it to create a cache one time programmatically and then only if the key is not found then create a [new entry in the] cache. If everything looks okay the problem is getting the id of product. Please advise. I have included the code and xml file.
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;
}
Here is the xml file:
<Products>
<Product>
<ProductName>PDPArch</ProductName>
<ProductId>57947</ProductId>
</Product>
<Product>
<ProductName>TYFTType</ProductName>
<ProductId>94384</ProductId>
</Product>
</Products>

Answer 1

To get the product id of, say, "TYFTType", you would need this XPath expression:
/Products/Product[ProductName = 'TYFTType']/ProductId
So what about something along the lines of (untested, but you get the idea):
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;
}
The above has two little issues:
It will not remember the non-existent product names.
Product names must not contain a single quote or the XPath expression will break. You should add a check for this condition.