Linq to XML查询分析

Question

This query does work but I am not sure it is proper way to write this kind of query. I feel it is using too many Descendants and Parent.

Is there a better way to write this query?

There can be more than one catalog in XML.

static IEnumerable<Parts> GetAllParts(XDocument doc, string catalog, string groupId, string subGroupId)
    {
        var parts = (from p in doc.Descendants("ROOT").Descendants("CATALOG").Descendants("GROUP").Descendants("SUBGROUP").Descendants("BOM").Descendants("PARTS")
                     where (string)p.Parent.Parent.Parent.Parent.Element("IDENT").Value == catalog
                            && p.Parent.Parent.Parent.Element("IDENT").Value == groupId
                            && p.Parent.Parent.Element("IDENT").Value == subGroupId

                     select new Parts
                     {
                         ObjectId = int.Parse(p.Attribute("OBJECTID").Value),
                         Ident = p.Element("IDENT").Value,
                         List = p.Element("LIST").Value,
                         Descr = p.Element("DESC").Value
                     });


        return parts;

    }
}

public class Parts
{
    public int ObjectId { get; set;}
    public string Descr { get; set; }
    public string Ident { get; set;  }
    public string List { get; set; }
}

Update: XML added.

<ROOT>
    <CATALOG>
        <OBJECT_ID>001</OBJECT_ID>
        <OBJECT_IDENT>X001</OBJECT_IDENT>
        <GROUP>
            <OBJECT_ID>1001</OBJECT_ID>
            <OBJECT_IDENT>01</OBJECT_IDENT>
            <NAME>HOUSING</NAME>

            <SUBGROUP>              
                <OBJECT_ID>5001</OBJECT_ID>
                <OBJECT_IDENT>01.05</OBJECT_IDENT>
                <NAME>DESIGN GROUP 1</NAME>
                <BOM>
                    <OBJECT_ID>6001</OBJECT_ID>
                    <OBJECT_IDENT>010471</OBJECT_IDENT>
                    <PARTS>
                        <OBJECT_ID>2316673</OBJECT_ID>
                        <OBJECT_IDENT>A002010660</OBJECT_IDENT>
                        <DESC>SHORT BLOCK</DESC>
                        <NOTES>
                            <ROW>
                                <NOTES>Note 1</NOTES>
                                <BOM>010471</BOM>
                                <POS>1</POS>
                            </ROW>
                            <ROW>
                                <NOTES>Note 2</NOTES>
                                <BOM>010471</BOM>
                                <POS>2</POS>
                            </ROW>
                        </NOTES>
                    </PARTS>
                    <PARTS>
                    </PARTS>
                    <PARTS>
                    </PARTS>
                </BOM>
            </SUBGROUP>

            <SUBGROUP>              
            </SUBGROUP>
            <SUBGROUP>              
            </SUBGROUP>

        </GROUP>

        <GROUP>
        </GROUP>

    </CATALOG>
</ROOT>

Answer 1

Some suggestions regarding your question (I hope you'll improve your future posts) :

1. Your code and the XML posted doesn't work. For instance, the XML has <OBJECT_IDENT> element, but your LINQ has IDENT . Please craft it carefully and make sure it does work to avoid confusion.

2. Please put some effort in explaining the problem and giving clarification. "I am retrieving Parts data as function name says" is not clear enough as simply getting <Parts> elements doesn't need filtering but your LINQ has where .... clause.

3. This question seems to suits better in https://codereview.stackexchange.com/

And here is some suggestions regarding your code :

1. Use .Elements() to get direct child of current node as opposed to Descendants() which get all descendat nodes.

2. You can use Elements().Where() to filter the element so you can avoid traversing Parent s

3. You can cast XElement to string / int to avoid exception in case such element not found

Example code snippet :

var parts = (from p in doc.Root
              .Elements("CATALOG").Where(o => catalog == (string)o.Element("OBJECT_IDENT"))
              .Elements("GROUP").Where(o => groupId == (string)o.Element("OBJECT_IDENT"))
              .Elements("SUBGROUP").Where(o => subGroupId == (string)o.Element("OBJECT_IDENT"))
              .Elements("BOM")
              .Elements("PARTS")
             select new Parts
             {
                 ObjectId = (int)p.Element("OBJECT_ID"),
                 Ident = (string)p.Element("OBJECT_IDENT"),
                 List = (int)p.Element("LIST"),
                 Descr = (string)p.Element("DESC")
             });