LINQ Advice

[DeanMc]

So I was speaking to Mendhak earlier about this and whether xPath would be better. So heres the code:

        private void PopulateList(String SourceType, String OutputType)
        {
            //Populate The ListOfSubRules Property using LINQ to XML
            XDocument XMLDataStore = XDocument.Load("DataStore.xml");

            var XMLSubRules = from XMLSubRule in XMLDataStore.Descendants("SubRule")
                              where (XMLSubRule.Attribute("SourceType").Value == SourceType && XMLSubRule.Attribute("OuputType").Value == OutputType)
                              select new
                              {
                                  Expression = XMLSubRule.Element("Expression").Value,
                                  OpeningElement = XMLSubRule.Element("OpeningElement").Value,
                                  ClosingElement = XMLSubRule.Element("ClosingElement").Value
                              };

            foreach (var XMLSubRule in XMLSubRules)
            {
                SubRule SubRuleItem = new SubRule(XMLSubRule.Expression,
                                                  XMLSubRule.OpeningElement,
                                                  XMLSubRule.ClosingElement);
                ListOfSubRules.Add(SubRuleItem);
            }

 

        }

[DeanMc]

This is the Data it is operating on:

<?xml version="1.0" encoding="utf-8" ?>
<Store>
  <SubRules>
    
    <SubRule SourceType="XAML" OutputType="BBCODE">
      <Name>Get Tags</Name>
      <Expression>&lt;/|&lt;|&gt;|/&gt;</Expression>
      <OpeningElement></OpeningElement>
      <ClosingElement></ClosingElement>
    </SubRule>

    <SubRule SourceType="XAML" OutputType="BBCODE">
      <Name>Get Property Values</Name>
      <Expression>=&quot;[()\[\]\w#,. =:/-{}]+&quot;</Expression>
      <OpeningElement></OpeningElement>
      <ClosingElement></ClosingElement>
    </SubRule>

    <SubRule SourceType="XAML" OutputType="BBCODE">
      <Name>Get Object Names</Name>
      <Expression>(?&lt;=&lt;/|&lt;)[\w:.]+</Expression>
      <OpeningElement></OpeningElement>
      <ClosingElement></ClosingElement>
    </SubRule>

    <SubRule SourceType="XAML" OutputType="BBCODE">
      <Name>Get Property Names</Name>
      <Expression>\b[\w:.]+(?=\=&quot;)</Expression>
      <OpeningElement></OpeningElement>
      <ClosingElement></ClosingElement>
    </SubRule>
    
    
  </SubRules>

  <FormatBoxes>
    
  </FormatBoxes>
</Store>

And to be honest I'm not happy with the document structure either I would like to change that!

[DeanMc]

And yes the program does know what data to expect and where (Or at least it should!)

[mendhak]

So with the XPathNavigator you'd use something like

foreach(XpathNavigator subRuleNode in xmlDataStore.Select("/Store/SubRules/SubRule"))
{
SubRule subRuleItem = new SubRule(subRuleNode.SelectSingleNode("Expression").Value, subRuleNode.SelectSingleNode("OpeningElement").Value, subRuleNode.SelectSingleNode("ClosingElement").Value
ListOfSubRules.Add(subRuleItem);
}

My gripe with .Descendants is that it is equivalent to

xmlDataStore.Select("//SubRule")

which is equivalent to

myXmlDocument.SelectNodes("//SubRule")

which does a recursive search across node names. The // (double slash) was introduced for 'unknown' XML data, in which you knew a node existed, but didn't know the XML structure or where the node would be.

Since you mentioned that this is going to be read-only, I would use XpathNavigator over XmlDocument.

[DeanMc]

Cool, My only issue with that code is that it gets EVERY subrule item, which I do not what. Can I add a LINQ satement here to query the data more specificly?

SubRule subRuleItem = new SubRule(subRuleNode.SelectSingleNode("Expression").Value, subRuleNode.SelectSingleNode("OpeningElement").Value, subRuleNode.SelectSingleNode("ClosingElement").Value

[mendhak]

Oh! I see, you're calling it in a function. Yeah, that's easily done too.

foreach(XpathNavigator subRuleNode in xmlDataStore.Select("/Store/SubRules/SubRule[@SourceType='" + theParameterPassedToThisFunction + ']"))
{
SubRule subRuleItem = new SubRule(subRuleNode.SelectSingleNode("Expression").Value, subRuleNode.SelectSingleNode("OpeningElement").Value, subRuleNode.SelectSingleNode("ClosingElement").Value
ListOfSubRules.Add(subRuleItem);
}

The [] square brackets is like a 'where', and the @SourceType means the @ttribute named SourceType.

[DeanMc]

Ok, I see what you doing. I must look up more XML and LINQ as im sure there is a better method than .Descendants. I will have a look at xpath too and the DataStore's structure and see how I go from there.