Collection < T > Class提供通用集合的基类。 T是集合中元素的类型。此类位于System.Collections.ObjectModel命名空间下。
特征：
- 通过创建其构造类型之一的实例，可以立即使用Collection < T>类。
- Collection < T >类提供了受保护的方法，可用来自定义其在添加和删除项目，清除集合或设置现有项目的值时的行为。
- 大多数Collection < T >对象都可以修改。但是，使用只读IList < T >对象初始化的Collection对象不能被修改。
- 可以使用整数索引访问此集合中的元素。此集合中的索引从零开始。
- Collection < T >接受null作为引用类型的有效值，并允许重复的元素。
建设者
| Constructor | Description |
|---|---|
| Collection<T>() | Initializes a new instance of the Collection<T> class that is empty. |
| Collection<T>(IList<T>) | Initializes a new instance of the Collection<T> class as a wrapper for the specified list. |
例子：
// C# code to create a Collection
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
class GFG {
// Driver code
public static void Main()
{
// Creating a collection of ints
Collection myColl = new Collection();
// Adding elements in Collection myColl
myColl.Add(2);
myColl.Add(3);
myColl.Add(4);
myColl.Add(5);
// Displaying the elements in myColl
foreach(int i in myColl)
{
Console.WriteLine(i);
}
}
}
输出：
2
3
4
5
特性
| Property | Description |
|---|---|
| Count | Gets the number of elements actually contained in the Collection<T>. |
| Items | Gets a IList<T> wrapper around the Collection<T>. |
| Item[Int32] | Gets or sets the element at the specified index. |
例子：
// C# Code to illustrate the
// Properties of Collection class
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
class GFG {
// Driver code
public static void Main()
{
// Creating a collection of strings
Collection myColl = new Collection();
// Adding elements in Collection myColl
myColl.Add("A");
myColl.Add("B");
myColl.Add("C");
myColl.Add("D");
myColl.Add("E");
// ------- Count Property ----------
// To print the count of
// elements in Collection
Console.WriteLine("Count : " + myColl.Count);
// -------- Item[Int32] Property --------
// Get the element at index 2
Console.WriteLine("Element at index 2 is : " + myColl[2]);
// Get the element at index 3
Console.WriteLine("Element at index 3 is : " + myColl[3]);
}
}
输出：
Count : 5
Element at index 2 is : C
Element at index 3 is : D
方法
| Method | Description |
|---|---|
| Add(T) | Adds an object to the end of the Collection<T>. |
| Clear() | Removes all elements from the Collection<T>. |
| ClearItems() | Removes all elements from the Collection<T>. |
| Contains(T) | Determines whether an element is in the Collection<T>. |
| CopyTo(T[], Int32) | Copies the entire Collection<T> to a compatible one-dimensional Array, starting at the specified index of the target array. |
| Equals(Object) | Determines whether the specified object is equal to the current object. |
| GetEnumerator() | Returns an enumerator that iterates through the Collection<T>. |
| GetHashCode() | Serves as the default hash function. |
| GetType() | Gets the Type of the current instance. |
| IndexOf(T) | Searches for the specified object and returns the zero-based index of the first occurrence within the entire Collection<T>. |
| Insert(Int32, T) | Inserts an element into the Collection<T> at the specified index. |
| InsertItem(Int32, T) | Inserts an element into the Collection at the specified index. |
| MemberwiseClone() | Creates a shallow copy of the current Object. |
| Remove(T) | Removes the first occurrence of a specific object from the Collection<T>. |
| RemoveAt(Int32) | Removes the element at the specified index of the Collection<T>. |
| RemoveItem(Int32) | Removes the element at the specified index of the Collection<T>. |
| SetItem(Int32, T) | Replaces the element at the specified index. |
| ToString() | Returns a string that represents the current object. |
例子：
// C# code to check if an
// element is in the Collection
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
class GFG {
// Driver code
public static void Main()
{
// Creating a collection of strings
Collection myColl = new Collection();
myColl.Add("A");
myColl.Add("B");
myColl.Add("C");
myColl.Add("D");
myColl.Add("E");
// Checking if an element is in the Collection
// The function returns "True" if the
// item is present in Collection
// else returns "False"
Console.WriteLine(myColl.Contains("A"));
}
}
输出：
True
范例2：
// C# code to copy the entire Collection
// to a compatible one-dimensional Array,
// starting at the specified index of
// the target array
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
class GFG {
// Driver code
public static void Main()
{
// Creating a collection of strings
Collection myColl = new Collection();
myColl.Add("A");
myColl.Add("B");
myColl.Add("C");
myColl.Add("D");
myColl.Add("E");
// Creating a string array
string[] myArr = new string[myColl.Count];
// Copying the entire Collection to a
// compatible one-dimensional Array,
// starting at the specified index
// of the target array
myColl.CopyTo(myArr, 0);
// Displaying the elements in myArr
foreach(string str in myArr)
{
Console.WriteLine(str);
}
}
}
输出：
A
B
C
D
E
参考：
- https://docs.microsoft.com/zh-cn/dotnet/api/system.collections.objectmodel.collection-1?view=netframework-4.7.2