/// <summary>
/// Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.
/// </summary>
/// <param name="predicate">A function to test an element for a condition.</param>
/// <param name="source">The sequence to type as <see cref="IEnumerable{T}"/>.</param>
/// <typeparam name="TData">The type of the elements of source.</typeparam>
/// <returns>The first element of the sequence.</returns>
/// <exception cref="ArgumentNullException"><paramref name="predicate"/> is null.</exception>
/// <exception cref="InvalidOperationException">The sequence is empty.</exception>
public static TData First <TData>(this AzureDocumentDbDataStore <TData> source, Func <TData, bool> predicate)
where TData : AzureDocumentDbEntity
{
IList <TData> result = source.Where(predicate).AsEnumerable().ToList();
return(result.First());
}
/// <summary>
/// Returns the first element of the sequence.
/// </summary>
/// <param name="source">The sequence to type as <see cref="IEnumerable{T}"/>.</param>
/// <typeparam name="TData">The type of the elements of source.</typeparam>
/// <returns>The first element of the sequence.</returns>
/// <exception cref="InvalidOperationException">The sequence contains more than one element, or the sequence is empty.</exception>
public static TData First <TData>(this AzureDocumentDbDataStore <TData> source)
where TData : AzureDocumentDbEntity
{
return(source.AsEnumerable().ToList().First());
}
