如何找到xml元素的Min和Max值

Question

Can anyone help me with this problem?

I have to find the Min and Max months according to expenses values:

<?xml version="1.0" encoding="UTF-8"?>
<shop>
   <month>Jan</month>
   <expense>2520,50€</expense>
   <month>Feb</month>
   <expense>2900,00€</expense>
   <month>Mar</month>
   <expense>1000,00€</expense>
   <month>Apr</month>
   <expense>1520,00€</expense>
   <month>May</month>
   <expense>500,00€</expense>
   <month>Jun</month>
   <expense>1250,50€</expense>
   <month>Jul</month>
   <expense>300,00€</expense>
   <month>Aug</month>
   <expense>0,00€</expense>
 </shop>

I already tried with XPath but without success...

XmlDocument doc = new XmlDocument();
doc.Load("XML/despesas.xml");

XmlNode node = doc.SelectSingleNode("//shop/expense[not(. <=../preceding-sibling::expense) and not(. <=../following-sibling::expense)]");
int min = Convert.ToInt32(node.Value);

Answer 1

You need to read the xml, then find the Min/Max of the expenses and the corresponding month.

Here is one O(n) way to find the Month with Min/Max expense.

var xmlString = File.ReadAllText(@"C:\YourDirectory\YourFile.xml");

var xDoc = XDocument.Parse(xmlString);
var months = xDoc.Descendants("month");
var expenses = xDoc.Descendants("expense");

var cultureInfo = new CultureInfo("fr-FR");

decimal maxExp = decimal.MinValue;
decimal minExp = decimal.MaxValue;
string maxExpMonth = string.Empty; //=> "Feb"
string minExpMonth = string.Empty; //=> "Aug"
for (int i = 0; i < expenses.Count(); i++)
{
    var exp = decimal.Parse(expenses.ElementAt(i).Value, NumberStyles.Currency, cultureInfo);
    if (exp > maxExp)
    {
        maxExp = exp;
        maxExpMonth = months.ElementAt(i).Value;
    }
    if (exp < minExp)
    {
        minExp = exp;
        minExpMonth = months.ElementAt(i).Value;
    }
}

Answer 2

You could XElement and then getall the expense elements. To get just the interger value, you would need to remove the currency symbol as shown below.

var parsedXml = XElement.Parse(xmlToParse);
var expenses = (from e1 in parsedXml.Elements("expense")
                select int.Parse(Regex.Replace(e1.Value,"[^0-9]", string.Empty))).ToList();
var minValue = expenses.Min();
var maxValue =  expenses.Max();

Answer 3

Instead of using XPath, I suggest to use Linq to XML . You can then parse the elements into memory and query them a lot better. You can use the following sample to get the min and the max values:

void Main()
{
    const string content = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" + 
                                "<shop>" + 
                                   "<month>Jan</month>" + 
                                   "<expense>2520,50€</expense>" + 
                                   "<month>Feb</month>" + 
                                   "<expense>2900,00€</expense>" + 
                                   "<month>Mar</month>" + 
                                   "<expense>1000,00€</expense>" + 
                                   "<month>Apr</month>" + 
                                   "<expense>1520,00€</expense>" + 
                                   "<month>May</month>" + 
                                   "<expense>500,00€</expense>" + 
                                   "<month>Jun</month>" + 
                                   "<expense>1250,50€</expense>" + 
                                   "<month>Jul</month>" + 
                                   "<expense>300,00€</expense>" + 
                                   "<month>Aug</month>" + 
                                   "<expense>0,00€</expense>" + 
                                 "</shop>";
    var doc = XDocument.Parse(content);
    var elements = doc.Element("shop")  // Element shop
                        .Elements()     // All elements under shop
                        .Select((x, i) => new { Index = i, Element = x }) // Get index for grouping
                        .GroupBy(x => x.Index / 2)  // Group by index so that month and expense element are contained in a group
                        .Select(x => new { Month = x.ElementAt(0).Element.Value, Expense = decimal.Parse(x.ElementAt(1).Element.Value, System.Globalization.NumberStyles.Any) })    // Parse into anonymous type
                        .OrderBy(x => x.Expense)    // Order by expense
                        .ToArray(); // Execute query
    var min = elements.FirstOrDefault();
    var max = elements.LastOrDefault();
}

At the beginning, you load the XML into an XDocument. In this sample, I parse the string, but you can also use the Load method to read a file.

The query is a bit complicated; first, you get all the elements under shop . You then select them into an anonymous type that also contains the index of the element. The index is used to build groups that contain month and expense.

Then, a new anonymous type is created that contains both month and expense (as a decimal) in a single object. Please note that parsing the value of expense into a decimal is culture dependent. In the sample, I do not specify a culture, but this might be required in a real world scenario. The resulting list is sorted by Expense in ascending order.

By using FirstOrDefault and LastOrDefault respectively, you can retrieve the min and max values.