| #region Apache License |
| // |
| // Licensed to the Apache Software Foundation (ASF) under one or more |
| // contributor license agreements. See the NOTICE file distributed with |
| // this work for additional information regarding copyright ownership. |
| // The ASF licenses this file to you under the Apache License, Version 2.0 |
| // (the "License"); you may not use this file except in compliance with |
| // the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| // |
| #endregion |
| |
| using System; |
| using System.Collections; |
| |
| namespace log4net.Util |
| { |
| /// <summary> |
| /// An always empty <see cref="ICollection"/>. |
| /// </summary> |
| /// <remarks> |
| /// <para> |
| /// A singleton implementation of the <see cref="ICollection"/> |
| /// interface that always represents an empty collection. |
| /// </para> |
| /// </remarks> |
| /// <author>Nicko Cadell</author> |
| /// <author>Gert Driesen</author> |
| #if !NETCF |
| [Serializable] |
| #endif |
| public sealed class EmptyCollection : ICollection |
| { |
| #region Private Instance Constructors |
| |
| /// <summary> |
| /// Initializes a new instance of the <see cref="EmptyCollection" /> class. |
| /// </summary> |
| /// <remarks> |
| /// <para> |
| /// Uses a private access modifier to enforce the singleton pattern. |
| /// </para> |
| /// </remarks> |
| private EmptyCollection() |
| { |
| } |
| |
| #endregion Private Instance Constructors |
| |
| #region Public Static Properties |
| |
| /// <summary> |
| /// Gets the singleton instance of the empty collection. |
| /// </summary> |
| /// <returns>The singleton instance of the empty collection.</returns> |
| /// <remarks> |
| /// <para> |
| /// Gets the singleton instance of the empty collection. |
| /// </para> |
| /// </remarks> |
| public static EmptyCollection Instance |
| { |
| get { return s_instance; } |
| } |
| |
| #endregion Public Static Properties |
| |
| #region Implementation of ICollection |
| |
| /// <summary> |
| /// Copies the elements of the <see cref="ICollection"/> to an |
| /// <see cref="Array"/>, starting at a particular Array index. |
| /// </summary> |
| /// <param name="array">The one-dimensional <see cref="Array"/> |
| /// that is the destination of the elements copied from |
| /// <see cref="ICollection"/>. The Array must have zero-based |
| /// indexing.</param> |
| /// <param name="index">The zero-based index in array at which |
| /// copying begins.</param> |
| /// <remarks> |
| /// <para> |
| /// As the collection is empty no values are copied into the array. |
| /// </para> |
| /// </remarks> |
| public void CopyTo(System.Array array, int index) |
| { |
| // copy nothing |
| } |
| |
| /// <summary> |
| /// Gets a value indicating if access to the <see cref="ICollection"/> is synchronized (thread-safe). |
| /// </summary> |
| /// <value> |
| /// <b>true</b> if access to the <see cref="ICollection"/> is synchronized (thread-safe); otherwise, <b>false</b>. |
| /// </value> |
| /// <remarks> |
| /// <para> |
| /// For the <see cref="EmptyCollection"/> this property is always <c>true</c>. |
| /// </para> |
| /// </remarks> |
| public bool IsSynchronized |
| { |
| get { return true; } |
| } |
| |
| /// <summary> |
| /// Gets the number of elements contained in the <see cref="ICollection"/>. |
| /// </summary> |
| /// <value> |
| /// The number of elements contained in the <see cref="ICollection"/>. |
| /// </value> |
| /// <remarks> |
| /// <para> |
| /// As the collection is empty the <see cref="Count"/> is always <c>0</c>. |
| /// </para> |
| /// </remarks> |
| public int Count |
| { |
| get { return 0; } |
| } |
| |
| /// <summary> |
| /// Gets an object that can be used to synchronize access to the <see cref="ICollection"/>. |
| /// </summary> |
| /// <value> |
| /// An object that can be used to synchronize access to the <see cref="ICollection"/>. |
| /// </value> |
| /// <remarks> |
| /// <para> |
| /// As the collection is empty and thread safe and synchronized this instance is also |
| /// the <see cref="SyncRoot"/> object. |
| /// </para> |
| /// </remarks> |
| public object SyncRoot |
| { |
| get { return this; } |
| } |
| |
| #endregion Implementation of ICollection |
| |
| #region Implementation of IEnumerable |
| |
| /// <summary> |
| /// Returns an enumerator that can iterate through a collection. |
| /// </summary> |
| /// <returns> |
| /// An <see cref="IEnumerator"/> that can be used to |
| /// iterate through the collection. |
| /// </returns> |
| /// <remarks> |
| /// <para> |
| /// As the collection is empty a <see cref="NullEnumerator"/> is returned. |
| /// </para> |
| /// </remarks> |
| public IEnumerator GetEnumerator() |
| { |
| return NullEnumerator.Instance; |
| } |
| |
| #endregion Implementation of IEnumerable |
| |
| #region Private Static Fields |
| |
| /// <summary> |
| /// The singleton instance of the empty collection. |
| /// </summary> |
| private readonly static EmptyCollection s_instance = new EmptyCollection(); |
| |
| #endregion Private Static Fields |
| } |
| } |