C# |数组。FindLast()方法

原文:https://www . geesforgeks . org/c-sharp-array-find last-method/

此方法用于搜索与指定谓词定义的条件相匹配的元素，返回整个数组中最后一次出现的。

语法:

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

参数:

数组:是一维的，从零开始搜索的数组。匹配:是定义要搜索的元素的条件的谓词。

返回值:如果找到匹配指定谓词定义的条件的最后一个元素，则该方法返回该元素，否则返回类型 t 的默认值

异常:如果阵为空或匹配为空，则此方法抛出 ArgumentNullException 。

下面的程序说明了数组的使用。FindLast(T[]，谓词)方法 :

例 1:

c sharp . c sharp . c sharp . c sharp

// C# program to demonstrate
// Array.FindLast(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
            String[] myArr = {"Sun", "Son", "Tue", "Thu"};

            // Display the values of the myArr.
            Console.WriteLine("Initial Array:");

            // calling the PrintIndexAndValues()
            // method to print
            PrintIndexAndValues(myArr);

            // getting a last element with required
            // condition using method FindLast()
            string value = Array.FindLast(myArr, 
                   element => element.StartsWith("S",
                          StringComparison.Ordinal));

            // Display the value of
            // the found element.
            Console.Write("Last occurrence: ");

            // 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();
    }
}

Output:

Initial Array:
Sun
Son
Tue
Thu

Last occurrence: Son

例 2:

c sharp . c sharp . c sharp . c sharp

// C# program to demonstrate
// Array.FindLast(T[], Predicate<T>)
// Method
using System;
using System.Collections.Generic;

public class GFG {

    // Main Method
    public static void Main()
    {

        try {

            // Creating and initializing
            // new Array String with null
            String[] myArr = null;

            // getting a last element with required
            // condition using method FindLast()
            string value = Array.FindLast(myArr,
                element => element.StartsWith("S",
                       StringComparison.Ordinal));

            // Display the value of
            // the found element.
            Console.Write("Last occurrence: ");

            // 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();
    }
}

Output:

Exception Thrown: System.ArgumentNullException

参考:

https://docs . Microsoft . com/en-us/dotnet/API/system . array . find last？视图=netframework-4.7.2

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