public void TestEmptyRemainerMoveNextReturnedFalse()
{
IEnumerable <int> sequence = new int[] { 0 };
IEnumerator <int> enumerator = new DisposableEnumerator(sequence.GetEnumerator());
enumerator.MoveNext();
enumerator.MoveNext();
var result = enumerator.ToEnumerable(includeCurrent: null);
var expected = sequence.Skip(1);
Assert.IsTrue(expected.SequenceEqual(result));
}
/// <summary>
/// Returns the sequence skipping the specified index.
/// </summary>
/// <exception cref="ArgumentNullException"/>
/// <exception cref="ArgumentOutOfRangeException"/>
public static IEnumerable SkipIndex(this IEnumerable source, int index)
{
Error.ThrowIfNull(source, nameof(source));
Error.ThrowIfBelowRange(index, nameof(index), 0);
int currentIndex = -1;
bool skipped = false;
using DisposableEnumerator enumerator = new DisposableEnumerator(source.GetEnumerator());
while (enumerator.MoveNext())
{
++currentIndex;
if (currentIndex != index)
{
yield return(enumerator.Current);
}
else
{
skipped = true;
}
}
if (!skipped)
{
Error.ThrowArgumentOutOfRange(nameof(index));
}
}
/// <summary>
/// Returns the specified collection while inserting the collection specified starting from the specified index.
/// </summary>
/// <param name="items">the collection to be inserted</param>
/// <exception cref="ArgumentNullException"/>
/// <exception cref="ArgumentOutOfRangeException"/>
/// <exception cref="InvalidOperationException"/>
public static IEnumerable EnumerableInsert(this IEnumerable source, int index, IEnumerable items)
{
Error.ThrowIfNull(source, nameof(source));
Error.ThrowIfBelowRange(index, nameof(index), 0);
int counter = 0;
using (DisposableEnumerator enumerator = new DisposableEnumerator(source.GetEnumerator()))
{
while (enumerator.MoveNext())
{
if (counter == index)
{
foreach (object item in items)
{
yield return(item);
}
}
yield return(enumerator.Current);
++counter;
}
}
if (counter == index)
{
foreach (object item in items)
{
yield return(item);
}
}
else if (counter < index)
{
Error.ThrowArgumentOutOfRange(nameof(index));
}
}
/// <summary>
/// Returns the specified collection while inserting the item specified at the specified index.
/// </summary>
/// <param name="item">the item to be inserted</param>
/// <exception cref="ArgumentNullException"/>
/// <exception cref="ArgumentOutOfRangeException"/>
/// <exception cref="InvalidOperationException"/>
public static IEnumerable EnumerableInsert(this IEnumerable source, int index, object item)
{
Error.ThrowIfNull(source, nameof(source));
Error.ThrowIfBelowRange(index, nameof(index), 0);
int counter = 0;
using (DisposableEnumerator enumerator = new DisposableEnumerator(source.GetEnumerator()))
{
while (enumerator.MoveNext())
{
if (counter == index)
{
yield return(item);
}
yield return(enumerator.Current);
++counter;
}
}
if (counter == index) //Insert to the end - same as EnumerableAdd
{
yield return(item);
}
else if (counter < index) //Index was greater than the last index if the item was to be added to the end
{
Error.ThrowArgumentOutOfRange(nameof(index));
}
}
public static object FirstOrNull(this IEnumerable source)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
IList collection = source as IList;
if (collection != null)
{
if (collection.Count > 0)
{
return(collection[0]);
}
}
else
{
using (DisposableEnumerator enumerator = source.GetDisposableEnumerator())
{
if (enumerator.MoveNext())
{
return(enumerator.Current);
}
}
}
return(null);
}
public static object First(this IEnumerable source)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
IList collection = source as IList;
if (collection != null)
{
if (collection.Count > 0)
{
return(collection[0]);
}
}
else
{
using (DisposableEnumerator enumerator = source.GetDisposableEnumerator())
{
if (enumerator.MoveNext())
{
return(enumerator.Current);
}
}
}
throw new InvalidOperationException("Sequence contains no elements");
}
public static bool Any(this IEnumerable source)
{
Error.ThrowIfNull(source, nameof(source));
using DisposableEnumerator e = new DisposableEnumerator(source.GetEnumerator());
if (e.MoveNext())
{
return(true);
}
return(false);
}
public static long LongCount(this IEnumerable source)
{
Error.ThrowIfNull(source, nameof(source));
long count = 0;
using DisposableEnumerator e = new DisposableEnumerator(source.GetEnumerator());
checked
{
while (e.MoveNext())
{
++count;
}
}
return(count);
}
public static bool Any(this IEnumerable source)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
using (DisposableEnumerator enumerator = source.GetDisposableEnumerator())
{
if (enumerator.MoveNext())
{
return(true);
}
}
return(false);
}
public static int Count(this IEnumerable source)
{
Error.ThrowIfNull(source, nameof(source));
if (source is ICollection collection)
{
return(collection.Count);
}
int count = 0;
using DisposableEnumerator e = new DisposableEnumerator(source.GetEnumerator());
checked
{
while (e.MoveNext())
{
++count;
}
}
return(count);
}
