C# Array.Find()用法及代碼示例

此方法用於搜索與指定謂詞定義的條件匹配的元素，並返回整個Array中的第一個匹配項。

用法:

public static T Find (T[] array, Predicate<T> match);

在此，T是數組元素的類型。

參數：

array: 它是要搜索的一維，從零開始的數組。
match: 謂詞定義了要搜索的元素的條件。

返回值：如果找到，則此方法返回與指定謂詞定義的條件匹配的第一個元素。否則，它將返回類型T的默認值。

異常：如果數組為null或match為null，則此方法引發ArgumentNullException。

以下示例程序旨在說明Array.Find(T []，Predicate)方法的用法：

示例1:

// C# program to demonstrate 
// Array.Find(T[], Predicate<T>) 
// Method  
using System; 
using System.Collections.Generic; 
  
public class GFG { 
  
    // Main Method 
    public static void Main() 
    { 
  
        try { 
  
            // Creating and intializing new the String 
            String[] myArr = {"Sun", "Mon", "Tue", "Thu"}; 
  
            // Display the values of the myArr. 
            Console.WriteLine("Initial Array:"); 
  
            // calling the PrintIndexAndValues() 
            // method to print 
            PrintIndexAndValues(myArr); 
  
            // getting a element a with required  
            // condition using method Find() 
            string value = Array.Find(myArr,  
                       element => element.StartsWith("S", 
                       StringComparison.Ordinal)); 
  
            // Display the value of  
            // the found element. 
            Console.Write("Element: "); 
  
            // printing the string  
            // following the condition 
            Console.Write("{0}", value); 
        } 
        catch (ArgumentNullException e) { 
  
            Console.Write("Exception Thrown: "); 
            Console.Write("{0}", e.GetType(), e.Message); 
        } 
    } 
  
    // Defining the method 
    // PrintIndexAndValues 
    public static void PrintIndexAndValues(String[] myArr) 
    { 
        for (int i = 0; i < myArr.Length; i++) { 
  
            Console.WriteLine("{0}", myArr[i]); 
        } 
        Console.WriteLine(); 
    } 
}

輸出：

Initial Array:
Sun
Mon
Tue
Thu

Element: Sun

示例2:

// C# program to demonstrate 
// Array.Find(T[], Predicate<T>) 
// Method  
using System; 
using System.Collections.Generic; 
  
public class GFG { 
  
    // Main Method 
    public static void Main() 
    { 
  
        try { 
  
            // Creating and initializing new  
            // the String with the null value 
            String[] myArr = null; 
  
            // getting an element a with  
            // required condition 
            // using method Find() 
            string value = Array.Find(myArr,  
                    element => element.StartsWith("S",  
                    StringComparison.Ordinal)); 
  
            // Display the value of  
            // the found element. 
            Console.Write("Element: "); 
  
            // printing the string  
            // following the condition 
            Console.Write("{0}", value); 
        } 
  
        catch (ArgumentNullException e) { 
  
            Console.Write("Exception Thrown: "); 
            Console.Write("{0}", e.GetType(), e.Message); 
        } 
    } 
  
    // Defining the method 
    // PrintIndexAndValues 
    public static void PrintIndexAndValues(String[] myArr) 
    { 
        for (int i = 0; i < myArr.Length; i++) { 
  
            Console.WriteLine("{0}", myArr[i]); 
        } 
        Console.WriteLine(); 
    } 
}

輸出：

Exception Thrown: System.ArgumentNullException

參考：

https://docs.microsoft.com/en-us/dotnet/api/system.array.find?view=netframework-4.7.2

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