... understanding of LINQ to Objects and just what LINQ can do for you, it’s time to learn about using LINQ to query and generate XML. This functionality is called LINQ to XML and, not so coincidentally, ... the same prototype but, this time, with elements in the input sequence, as shown in Listing 5 -38 .Listing 5 -38 . First Any Prototype Where Elements Are in the Source Input Sequencestring[] presidents ... source input sequence is null.ExamplesFor an example of the first prototype, I begin with a value that I know is not in my input sequence, as shown in Listing 5- 43 Listing 5- 43. First Contains Prototype...