c＃LINQ-to-XML更新（保存）订购后文件中的元素列表

Question

I have an XML file as such:

<?xml version="1.0" encoding="utf-8"?>
<FooMgr>
    <BlargDate>2017-03-06 10:26:21</BlargDate>
    <Bars>
        <Bar>
            <BarId>222</BarId>
            <BarVal>QWERTY</BarVal>
        </Bar>
        <Bar>
            <BarId>77</BarId>
            <BarVal>DVORAK</BarVal>
        </Bar>
        <Bar>
            <BarId>9999</BarId>
            <BarVal>AZERTY</BarVal>
        </Bar>
    </Bars>
</FooMgr>

and I am:

• reading it in
• adding a 'Bar' element
• ordering it descending by BarId
• attempting to save the updated/sorted xml back to the file.

although the added element is in the list after I save it, it does not keep the order I defined in code when saving. Here's what i go so far (mostly working valid code)

//read in the xml file
XDocument doc = XDocument.Load(...);

//add a new 'Bar' element
XElement bar1 = new XElement("Bar",
                      new XElement("BarId", 101),
                      new XElement("BarVal", "HCESAR"));
doc.Element("FooMgr").Element("Bars").Add(bar1);

//sort descending by BarId
IEnumerable<XElement> allBars = doc.Descendants("FooMgr")
                                   .Select(x => x.Element("Bars"))
                                   .Descendants("Bar")
                                   .ToArray();
allBars = allBars.OrderByDescending(s => int.Parse(s.Element("BarId").Value));

//save file
doc.Save(...);

// note: at this point the file successfully saves (along with the 
// new 'bar' value, but the order that is set for allBars does not 
// make it back into the file.

although this line:

allBars = allBars.OrderByDescending(s => int.Parse(s.Element("BarId").Value));

does seem to properly sort the 'Bars' elements in code, when I save it back to the file the order is not persisted.

Any thoughts?

Answer 1

You can do this before you call Save method:

//Remove bar elements from your doc
doc.Element("FooMgr").Element("Bars").Elements("Bar").Remove();
//Add the ordered bar nodes
doc.Element("FooMgr").Element("Bars").Add(allBars);

//save file
doc.Save(...);

More info about Remove extension method and Add method

Answer 2

First of all, your xml is not valid, i gues the right one will be:

<?xml version="1.0" encoding="utf-8"?>
<FooMgr>
    <BlargDate>2017-03-06 10:26:21</BlargDate>
    <Bars>
        <Bar>
            <BarId>222</BarId>
            <BarVal>QWERTY</BarVal>
        </Bar>
        <Bar>
            <BarId>77</BarId>
            <BarVal>DVORAK</BarVal>
        </Bar>
        <Bar>
            <BarId>9999</BarId>
            <BarVal>AZERTY</BarVal>
        </Bar>
    </Bars>
</FooMgr>

Your allBars is just a collection of nodes it doesn't belongs to any node, so you need to hang it under Bars, i would suggest first remove all items there:

XElement bar1 = new XElement("Bar",
    new XElement("BarId", 101),
    new XElement("BarVal", "HCESAR"));
doc.Element("FooMgr").Element("Bars").Add(bar1);

//sort descending by BarId
IEnumerable<XElement> allBars = doc.Descendants("FooMgr")
    .Select(x => x.Element("Bars"))
    .Descendants("Bar")
    .ToArray();

allBars = allBars.OrderByDescending(s => int.Parse(s.Element("BarId").Value));

doc.Element("FooMgr").Element("Bars").RemoveAll();
doc.Element("FooMgr").Element("Bars").Add(allBars);

Answer 3

In VB this would be

    Dim doc As XElement
    ' to load from a file
    'xe = XElement.Load(yourpath)
    ' for testing
    doc = <FooMgr>
              <BlargDate>2017-03-06 10:26:21</BlargDate>
              <Bars>
                  <Bar>
                      <BarId>222</BarId>
                      <BarVal>QWERTY</BarVal>
                  </Bar>
                  <Bar>
                      <BarId>77</BarId>
                      <BarVal>DVORAK</BarVal>
                  </Bar>
                  <Bar>
                      <BarId>9999</BarId>
                      <BarVal>AZERTY</BarVal>
                  </Bar>
              </Bars>
          </FooMgr>

    doc.<Bars>.LastOrDefault.Add(<Bar>
                                     <BarId>101</BarId>
                                     <BarVal>HCESAR</BarVal>
                                 </Bar>)

    Dim ie As List(Of XElement) = doc.<Bars>.Elements.OrderBy(Function(el) Integer.Parse(el.<BarId>.Value)).ToList
    doc.<Bars>.Elements.Remove()
    doc.<Bars>.FirstOrDefault.Add(ie)
    ' to save file
    ' doc.Save(yourpath)