Appending/concatenating two IEnumerable sequences

Question

I have two sets of datarows. They are each IEnumerable. I want to append/concatenate these two lists into one list. I\'m sure this is doable. I don\'t want to do a for loop

Answer 1

I just encountered a similar situation where I need to concatenate multiple sequences.

Naturally searched for existing solutions on Google/StackOverflow, however did not find anything the did not evaluate the enumerable, e.g. convert to array then use Array.Copy() etc., so I wrote an extension and static utiltiy method called ConcatMultiple.

Hope this helps anyone that needs to do the same.

/// 

/// Concatenates multiple sequences
/// 
/// The type of the elements of the input sequences.
/// The first sequence to concatenate.
/// The other sequences to concatenate.
/// 
public static IEnumerable ConcatMultiple(this IEnumerable first, params IEnumerable[] source)
{
    if (first == null)
        throw new ArgumentNullException("first");

    if (source.Any(x => (x == null)))
        throw new ArgumentNullException("source");

    return ConcatIterator(source);
}

private static IEnumerable ConcatIterator(IEnumerable first, params IEnumerable[] source)
{
    foreach (var iteratorVariable in first)
        yield return iteratorVariable;

    foreach (var enumerable in source)
    {
        foreach (var iteratorVariable in enumerable)
            yield return iteratorVariable;
    }
}

/// 

/// Concatenates multiple sequences
/// 
/// The type of the elements of the input sequences.        
/// The sequences to concatenate.
/// 
public static IEnumerable ConcatMultiple(params IEnumerable[] source)
{
    if (source.Any(x => (x == null)))
        throw new ArgumentNullException("source");

    return ConcatIterator(source);
}

private static IEnumerable ConcatIterator(params IEnumerable[] source)
{
    foreach (var enumerable in source)
    {
        foreach (var iteratorVariable in enumerable)
            yield return iteratorVariable;
    }
}