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.