Question

Using LINQ to XML, how can I join two sets of data based on ordinal position?

<document>
    <set1>
        <value>A</value>
        <value>B</value>
        <value>C</value>
    </set1>
    <set2>
        <value>1</value>
        <value>2</value>
        <value>3</value>
    </set2>
</document>

Based on the above fragment, I would like to join the two sets together such that “A” and “1” are in the same record, “B” and “2” are in the same record, and “C” and “3” are in the same record.

Answer 1

This is what the Enumerable.Zip extension does in .NET 4. You’d write it like so (assuming that this is the entire XDocument):

var set1Elements = document.Element("set1").Elements();
var set2Elements = document.Element("set2").Elements();
var results = set1Elements.Zip(set2Elements,
    (s1, s2) => new { Value1 = s1.Value, Value2 = s2.Value });

If you’re using .NET 3.5 or earlier, it’s not too difficult to write the Zip extension:

public static IEnumerable<TResult> Zip<TFirst, TSecond, TResult>(
    this IEnumerable<TFirst> first,
    IEnumerable<TSecond> second,
    Func<TFirst, TSecond, TResult> resultSelector)
{
    using (var firstEnumerator = first.GetEnumerator())
    using (var secondEnumerator = second.GetEnumerator())
    {
        while ((firstEnumerator.MoveNext() && secondEnumerator.MoveNext()))
        {
            yield return resultSelector(firstEnumerator.Current,
                secondEnumerator.Current);
        }
    }
}