IE可枚舉 C#

IEnumerable 是一個接口，它只定義了一個方法：GetEnumerator。該方法傳回一個 IEnumerator 介面。此介面用於迭代匿名類型的類別的列表或集合。它包含系統。 Collections.Generic 命名空間。它也用於與 LINQ 查詢表達式一起使用。這僅允許對集合進行唯讀訪問，然後可以使用 for-each 迴圈迭代繼承主集合的集合。 IEnumerable 介面是所有非通用列表的基本介面。 IEnumerable 介面有四種擴充方法。它們是 AsParallel()、AsQueryable()、Cast()、OfType()。本文將詳細解釋 IEnumerable 介面以及各種範例。

IEnumerable C# 的語法

文法如下：

public interface IEnumerable

使用 movenext() 和 reset() 方法迭代集合。

IEnumerable C# 中的擴充方法

方法如下：

• Cast(IEnumerable)：將 IEnumerable 介面的非泛型集合轉換為所提及的指定型別。
• OfType(IEnumerable)：依照所提及的型別過濾 IEnumerable 的元素。
• AsParallel(IEnumerable)：這用於啟用並行查詢的運行。
• AsQueryable(IEnumerable)：用於將 IEnumerable 介面轉換為 IQueryable 介面。

IEnumerable C# 實作範例

以下是範例：

範例#1

代碼：

using System;
using System.Diagnostics;
using System.Reflection;
using System.Collections;
namespace TestEg
{
class Test : IEnumerable
{
Test[] coll = null;
int Fi = 0;
public String Fname { get; set; }
public string lastnme { get; set; }
public Test()
{
coll = new Test[10];
}
public void Add(Test item)
{
coll[Fi] = item;
Fi++;
}
// IEnumerable Member
public IEnumeratorGetEnumerator()
{
foreach (object o in coll)
{
if(o == null)
{
break;
}
yield return o;
}
}
}
class Program
{
public static void Main(String[] args)
{
Test tobj = new Test();
tobj.Fname = "viki";
tobj.lastnme = "krish";
Test tobj1 = new Test();
tobj1.Fname = "nand";
tobj1.lastnme = "viki";
Test myList = new Test();
Test tobj2 = new Test();
tobj2.Fname = "vyapini";
tobj2.lastnme = "viki";
Test tobj3 = new Test();
tobj3.Fname = "tai";
tobj3.lastnme = "viki";
myList.Add(tobj);
myList.Add(tobj1);
myList.Add(tobj2);
myList.Add(tobj3);
foreach (Test obj in myList)
{
Console.WriteLine("Fname:" +  obj.Fname + "\t\t" + "lastnme :" + obj.lastnme);
}
Console.ReadLine();
}
}
}

輸出：

範例#2

代碼：

using System;
using System.Diagnostics;
using System.Reflection;
using System.Collections;
public class test : IEnumerable
{
public string Student1 { get; set; }
public string Student2 { get; set; }
public string Student3 { get; set; }
public IEnumeratorGetEnumerator() { return new testEnumerator(this); }
}
public class testEnumerator : IEnumerator
{
public testEnumerator(test ts) { _ts = ts; }
private test _ts;
private int _index = 0;
public void Reset() { _index = 0; Current = null; }
public object Current { get; private set; }
public bool MoveNext()
{
_index++;
/**/ if (_index == 1) { Current = _ts.Student1; return true; }
else if (_index == 2) { Current = _ts.Student2; return true; }
else if (_index == 3) { Current = _ts.Student3; return true; }
else return false;
}
}
class Program
{
public static void Main(String[] args)
{
varts = new test() {Student1 = "vignesh", Student2 = "nandhini", Student3 = "vyapini"};
foreach (string name in ts)
{
Console.WriteLine(name);
}
}
}

輸出：

範例#3

代碼：

using System.Linq;
using System.Collections.Generic;
using System;
namespace TestOper
{
public class testclass
{
public inteid { get; set; }
public string ename { get; set; }
public double salary { get; set; }
}
class Program
{
public static void Main()
{
List<testclass>listtestclasss = new List<testclass>
{
new testclass { eid= 1001, ename = "viki", salary = 1000 },
new testclass { eid= 1002, ename = "nandhini", salary = 600 },
new testclass { eid= 1003, ename = "vyapinin", salary = 10000 }
};
Dictionary<int, testclass>empdic = listtestclasss.ToDictionary(x =>x.eid);
foreach (KeyValuePair<int, testclass>kvp in empdic)
{
Console.WriteLine("eid" + kvp.Key + " ename : " + kvp.Value.ename + ", salary: " + kvp.Value.salary);
}
Console.ReadKey();
}
}
}

輸出：

範例#4

代碼：

using System;
using System.Collections.Generic;
using System.Linq;
class Program
{
static void Main()
{
int[] numbers = new int[]
{
1,13,51,75
};
Dictionary<int, bool>dic =
numbers.ToDictionary(v => v, v => true);
foreach (KeyValuePair<int, bool> pair in dic)
{
Console.WriteLine(pair);
}
List<string> names = new List<string>()
{
"vignesh","jagan","nyan","ravi","siva","sethu"
};
var result = names.ToDictionary(x => x, x => true);
if (result.ContainsKey("jagan"))
{
Console.WriteLine("name exists");
}
}
}

輸出：

範例#5

代碼：

using System;
using System.Collections.Generic;
using System.Linq;
namespace LINQDemo
{
class Program
{
static void Main(string[] args)
{
List<emp>sl = new List<emp>()
{
new emp(){empid = 1, empname = "James", empgender = "Male",eage=60},
new emp(){empid = 2, empname = "Sara", empgender = "Female",eage=90},
new emp(){empid = 3, empname = "Steve", empgender = "Male",eage=80},
new emp(){empid = 4, empname = "Pam", empgender = "Female",eage=70},
new emp(){empid = 5, empname = "James", empgender = "Male",eage=60},
new emp(){empid = 6, empname = "Sara", empgender = "Female",eage=50},
new emp(){empid = 7, empname = "Steve", empgender = "Male",eage=20},
new emp(){empid = 8, empname = "Pam", empgender = "Female",eage=40}
};
IQueryable<emp>iq = sl.AsQueryable()
.Where(t =>t.eage> 40);
foreach (varemp in iq)
{
Console.WriteLine( $"empid : {emp.empid}  empname : {emp.empname} eage : {emp.eage} empgender : {emp.empgender} ");
}
Console.ReadKey();
}
}
public class emp
{
public intempid { get; set; }
public string empname { get; set; }
public string empgender { get; set; }
public inteage { get; set; }
}
}

輸出：

結論

至此，文章詳細解說了C#中的IEnumerable。它還詳細解釋了 GetEnumerator 等各種方法以及與 IEnumerable 相關的其他擴展方法，例如 AsParallel()、AsQueryable()、Cast()、OfType()。它還透過範例演示了當前、下一個和重置方法的使用。要了解更多詳細信息，建議編寫範例程式並進行練習。

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