/// <summary>
/// This helper retrieves a projection of the first item of a sequence which satisfies a predicate.
/// </summary>
/// <typeparam name="TSource">The type of items inside the source sequence</typeparam>
/// <typeparam name="TResult">The type of the projection being retrieved from the sequence</typeparam>
/// <param name="source">The source from which the projection is retrieved</param>
/// <param name="predicate">The predicate that must be satisfied</param>
/// <param name="projector"></param>
/// <returns>The result of the get operation being performed</returns>
public static GetItemResult <TResult> GetFirst <TSource, TResult>(
IEnumerable <TSource> source,
Func <TSource, bool> predicate,
Func <TSource, TResult> projector)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (predicate == null)
{
throw new ArgumentNullException(nameof(predicate));
}
if (projector == null)
{
throw new ArgumentNullException(nameof(projector));
}
var firstMatch = source.FirstOrDefault(predicate);
var notFound = EqualityComparer <TSource> .Default.Equals(firstMatch, default(TSource));
if (notFound)
{
return(GetItemResult <TResult> .CreateForItemNotFound());
}
var projection = projector(firstMatch);
return(GetItemResult <TResult> .CreateForItemFound(projection));
}
public void CreateForItemNotFound_Creates_Instance_For_Failed_Get_Operation()
{
// ACT
var result = GetItemResult <string> .CreateForItemNotFound();
// ASSERT
Assert.IsNotNull(result);
Assert.IsFalse(result.Found);
Assert.IsNull(result.Item);
}