SingleOrDefault() throws an exception on more than one element

Question

I\'m getting an exception whenever I fetch like this

Feature f = o.Features.SingleOrDefault(e => e.LinkName == PageLink);

because this can r

Answer 1

Alternatively, if you only want the item when there is exactly one match and do not want to throw when there are more than one, this can be easily accomplished. I've created an extension method for this in my project:

public static class QueryableExtensions
{
    public static TSource SingleWhenOnly(this IQueryable source)
    {
        if (source == null)
            throw new ArgumentNullException("source");

        var results = source.Take(2).ToArray();

        return results.Length == 1 ? results[0] : default(TSource);
    }

    public static TSource SingleWhenOnly(this IQueryable source, Expression> predicate)
    {
        if (source == null)
            throw new ArgumentNullException("source");
        if (predicate == null)
            throw new ArgumentNullException("predicate");

        var results = source.Where(predicate).Take(2).ToArray();

        return results.Length == 1 ? results[0] : default(TSource);
    }
}