将List 转换为object

我正在寻找一个将List转换为object[]单行程序。 这是一个class轮，所以我对foreach等解决方案不感兴趣，或者for …

任何接受者？

提示：不， List.ToArray()和List.ToArray()都不起作用。

编辑：为什么List.ToArray()不起作用？ 因为它无法编译。

Answer 1

 mylist.Cast 

顺便说一句，这只会迭代一次，以防你想知道性能。 上）。 🙂

为什么？ 好吧，因为Cast将使用延迟执行，并且在ToArray()迭代列表之前实际上不会执行任何操作。

Answer 2

 List.Select(x => x as object).ToArray(); 

应该返回一个object[] 。

Answer 3

如果您没有Linq（.Net 3.0），那么您可以使用List中的ConvertAll（）和ToArray（）方法：

 List list = new List(); object[] objects = list.ConvertAll 

Answer 4

 theList.Cast 

要么

 new List 

Answer 5

对于LINQ之前的解决方案（仅适用于参考类型）。

 (object[])List.ToArray(); 

Answer 6

如果您不介意编写一个非常简短的可重用函数，ConvertAll扩展方法可能会有所帮助：

http://msdn.microsoft.com/en-us/library/73fe8cwf.aspx

编辑：

这也会奏效

 List intList = new List() { 1, 3, 4 }; object[] objectList = intList.ConvertAll(item => (object)item).ToArray(); 

Answer 7

在.NET 2.0上的C＃（VS 2008）中，以下编译并且不使用LINQ（据我所见）作为引用类型。

  object[] oArray; List oList = new List(); oArray = oList.ToArray(); 

这不需要强制转换，因为所有引用类型都以对象为基础。

Answer 8

我建议创建一个ListCastAdapter，

假设您要将列表转换为列表

创建IList实现的实现，该实现从List返回项

我很可能称之为ListCastAdapter类

祝你有美好的一天

实施（未测试）：

注意 ：建议将列表设置为ReadOnly，因为现在用户可以在原始列表中插入层次结构中的对象。

注意 ：未实现CopyTo（），您可以为数组创建相同的想法。

 using System.Collections; using System.Collections.Generic; namespace UDF.MyDataLayer { internal class ListCastAdapter : IList where T : class where S : class { private List adaptee; public ListCastAdapter(List adaptee ) { this.adaptee = adaptee; } #region Implementation of IEnumerable public class EnumeratorCastAdapter : IEnumerator { private IEnumerator adaptee; public EnumeratorCastAdapter(IEnumerator adaptee) { this.adaptee = adaptee; } #region Implementation of IDisposable /// 
 /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources. /// 
 /// 2 public void Dispose() { adaptee.Dispose(); } #endregion #region Implementation of IEnumerator /// 
 /// Advances the enumerator to the next element of the collection. /// 
 ///  /// true if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection. ///  /// The collection was modified after the enumerator was created. 2 public bool MoveNext() { return adaptee.MoveNext(); } /// 
 /// Sets the enumerator to its initial position, which is before the first element in the collection. /// 
 /// The collection was modified after the enumerator was created. 2 public void Reset() { adaptee.Reset(); } /// 
 /// Gets the element in the collection at the current position of the enumerator. /// 
 ///  /// The element in the collection at the current position of the enumerator. ///  public T Current { get { // needs to check if it is an Object or Value Type return adaptee.Current as T; } } /// 
 /// Gets the current element in the collection. /// 
 ///  /// The current element in the collection. ///  /// The enumerator is positioned before the first element of the collection or after the last element.2 object IEnumerator.Current { get { return Current; } } #endregion } /// 
 /// Returns an enumerator that iterates through the collection. /// 
 ///  /// A  that can be used to iterate through the collection. ///  /// 1 public IEnumerator GetEnumerator() { return new EnumeratorCastAdapter(adaptee.GetEnumerator()); } /// 
 /// Returns an enumerator that iterates through a collection. /// 
 ///  /// An  object that can be used to iterate through the collection. ///  /// 2 IEnumerator IEnumerable.GetEnumerator() { return adaptee.GetEnumerator(); } #endregion #region Implementation of ICollection /// 
 /// Adds an item to the . /// 
 /// The object to add to the .The  is read-only. public void Add(T item) { adaptee.Add(item as S); } /// 
 /// Removes all items from the . /// 
 /// The  is read-only.  public void Clear() { adaptee.Clear(); } /// 
 /// Determines whether the  contains a specific value. /// 
 ///  /// true if  is found in the ; otherwise, false. ///  /// The object to locate in the . public bool Contains(T item) { return adaptee.Contains(item as S); } /// 
 /// Copies the elements of the  to an , starting at a particular  index. /// 
 /// The one-dimensional  that is the destination of the elements copied from . The  must have zero-based indexing.The zero-based index in  at which copying begins. is null. is less than 0. is multidimensional.-or-The number of elements in the source  is greater than the available space from  to the end of the destination .-or-Type  cannot be cast automatically to the type of the destination . public void CopyTo(T[] array, int arrayIndex) { throw new System.NotImplementedException("Not Needed by Me, implement ArrayCastAdapter if needed"); } /// 
 /// Removes the first occurrence of a specific object from the . /// 
 ///  /// true if  was successfully removed from the ; otherwise, false. This method also returns false if  is not found in the original . ///  /// The object to remove from the .The  is read-only. public bool Remove(T item) { adaptee.Remove(item as S); } /// 
 /// Gets the number of elements contained in the . /// 
 ///  /// The number of elements contained in the . ///  public int Count { get { return adaptee.Count; } } /// 
 /// Gets a value indicating whether the  is read-only. /// 
 ///  /// true if the  is read-only; otherwise, false. ///  public bool IsReadOnly { get { return true; // change, to live on the edge } } #endregion #region Implementation of IList /// 
 /// Determines the index of a specific item in the . /// 
 ///  /// The index of  if found in the list; otherwise, -1. ///  /// The object to locate in the . public int IndexOf(T item) { return adaptee.IndexOf(item as S); } /// 
 /// Inserts an item to the  at the specified index. /// 
 /// The zero-based index at which  should be inserted.The object to insert into the . is not a valid index in the .The  is read-only. public void Insert(int index, T item) { adaptee.Insert(index, item as S); } /// 
 /// Removes the  item at the specified index. /// 
 /// The zero-based index of the item to remove. is not a valid index in the .The  is read-only. public void RemoveAt(int index) { adaptee.RemoveAt(index); } /// 
 /// Gets or sets the element at the specified index. /// 
 ///  /// The element at the specified index. ///  /// The zero-based index of the element to get or set. is not a valid index in the .The property is set and the  is read-only. public T this[int index] { get { return adaptee[index] as T; } set { adaptee[index] = value as S; } } #endregion } }