/// <summary>
/// Returns the single element of the source sequence, or default if empty.
/// </summary>
public static async Task <TSource> SingleOrDefaultAsync <TSource>(this IAsyncEnumerator <TSource> source)
{
int count = 0;
while (true)
{
bool success;
var value = source.TryGetNext(out success);
if (success)
{
count++;
if (count > 1)
{
throw MoreThanOneElement();
}
}
if (!(await source.MoveNextAsync().ConfigureAwait(false)))
{
if (count == 1)
{
return(value);
}
else
{
return(default(TSource));
}
}
}
}
public T TryGetNext(out bool success)
{
var id = Interlocked.Increment(ref counter);
Console.WriteLine($"[{label}] {this.id}:{id}> TryGetNext - Start");
var res = enumerator.TryGetNext(out success);
Console.WriteLine($"[{label}] {this.id}:{id}> TryGetNext - Stop({success}, {res})");
return(res);
}
/// <summary>
/// Returns true if all the elements of the source sequence match the predicate.
/// </summary>
public static async Task <bool> AllAsync <TSource>(this IAsyncEnumerator <TSource> source, Func <TSource, bool> predicate)
{
while (true)
{
bool success;
var value = source.TryGetNext(out success);
if (success && !predicate(value))
{
return(false);
}
if (!(await source.MoveNextAsync().ConfigureAwait(false)))
{
return(true);
}
}
}
/// <summary>
/// Returns the first element of the source sequence, or default if empty.
/// </summary>
public static async Task <TSource> FirstOrDefaultAsync <TSource>(this IAsyncEnumerator <TSource> source)
{
while (true)
{
bool success;
var value = source.TryGetNext(out success);
if (success)
{
return(value);
}
if (!(await source.MoveNextAsync().ConfigureAwait(false)))
{
return(default(TSource));
}
}
}
/// <summary>
/// Returns true if the source sequence contains an element.
/// </summary>
public static async Task <bool> AnyAsync <TSource>(this IAsyncEnumerator <TSource> source)
{
while (true)
{
bool success;
var value = source.TryGetNext(out success);
if (!success)
{
if (!(await source.MoveNextAsync().ConfigureAwait(false)))
{
return(false);
}
}
else
{
return(true);
}
}
}
/// <summary>
/// Converts the source <see cref="IAsyncEnumerator{T}"/> to a <see cref="List{T}"/>.
/// </summary>
public static async Task <List <TSource> > ToListAsync <TSource>(
this IAsyncEnumerator <TSource> source)
{
var list = new List <TSource>();
while (true)
{
bool success;
TSource value = source.TryGetNext(out success);
if (success)
{
list.Add(value);
}
else if (!(await source.MoveNextAsync().ConfigureAwait(false)))
{
return(list);
}
}
}
/// <summary>
/// Returns the count of elements in the source sequence that match the predicate.
/// </summary>
public static async Task <int> CountAsync <TSource>(this IAsyncEnumerator <TSource> source, Func <TSource, bool> predicate)
{
int count = 0;
while (true)
{
bool success;
var value = source.TryGetNext(out success);
if (!success)
{
if (!(await source.MoveNextAsync().ConfigureAwait(false)))
{
return(count);
}
}
else if (predicate(value))
{
count++;
}
}
}
/// <summary>
/// Returns the count of elements in the source sequence.
/// </summary>
public static async Task <int> CountAsync <TSource>(this IAsyncEnumerator <TSource> enumerator)
{
int count = 0;
while (true)
{
bool success;
var value = enumerator.TryGetNext(out success);
if (!success)
{
if (!(await enumerator.MoveNextAsync().ConfigureAwait(false)))
{
return(count);
}
}
else
{
count++;
}
}
}
public T TryGetNext(out bool success)
{
watch.Report("TryGetNext");
return(enumerator.TryGetNext(out success));
}
public T TryGetNext(out bool success) => _enumerator.TryGetNext(out success);