如何比较两个XML文档？

Question

I have two documents both are similar but I need to find an elegant and efficient way to compare the two files and return the values in Doc #1 that don't exist in Doc #2.

XML Doc #1

      <ids>
        <id>1</id>
        <id>2</id>
        <id>5</id>
        <id>6</id>
        <id>7</id>
        <id>8</id>
        <id>9</id>
       </ids>
    </ids>

XML Doc #2

  <ids>
    <id>1</id>
    <id>2</id>
    <id>7</id>
    <id>8</id>
    <id>9</id>
  </ids>

I was thinking about using linq if I could join these two documents on the id field. Is there a better way? I'm looking to return id #s 5 and 6.

Answer 1

Here is a sample that I know works, I only tried it out with small files (File1.xml had 20 items, File2.xml 8 items).

XDocument file1Doc = XDocument.Load("File1.xml");
XDocument file2Doc = XDocument.Load("File2.xml");

IEnumerable<string> file1Elements = from d in file1Doc.Descendants("Id")
                                    select d.Value;

IEnumerable<string> file2Elements = from d in file2Doc.Descendants("Id")
                                    select d.Value;

var difference = file1Elements.Except(file2Elements);

Alternatively, and likely more inline with what you seek is:

XDocument file1Doc = XDocument.Load("File1.xml");
XDocument file2Doc = XDocument.Load("File2.xml");

IEnumerable<string> file2Elements = from d in file2Doc.Descendants("Id")
                                    select d.Value;

var x = from include in file1Doc.Descendants("Id")
        where file2Elements.Contains(include.Value) != true
        select include;

You might also find some help looking at 101 LINQ Samples on MSDN .