C＃| Array.FindAll()方法

此方法用于检索与指定谓词定义的条件匹配的所有元素。

句法：

public static T[] FindAll (T[] array, Predicate match);

在此，T是数组元素的类型。

参数：

array: It is the one-dimensional, zero-based array to search.

match: It is the predicate that defines the conditions of the element to search for.

返回值：该方法返回一个数组，其中包含与指定谓词定义的条件相匹配的所有元素(如果找到)。否则，它将返回一个空数组。

异常：如果数组为null或match为null，则此方法将引发ArgumentNullException。

下面的程序说明了Array.FindAll(T []，Predicate的用法) 方法：

范例1：

// C# program to demonstrate
// FindAll() 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", "Sat"};
  
        // 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.FindAll(myArr, 
               element => element.StartsWith("S", 
               StringComparison.Ordinal));
  
        // Display the value 
        // of the found element.
        Console.WriteLine("Elements are: ");
  
        // printing the Array of String
        PrintIndexAndValues(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();
}
}

输出：

Initial Array:
Sun
Mon
Tue
Sat

Elements are: 
Sun
Sat

范例2：

// C# program to demonstrate
// FindAll() method
// For ArgumentNullException
using System;
using System.Collections.Generic;
  
public class GFG {
  
// Main Method
public static void Main()
{
  
    try {
  
        // Creating and initializing
        // new the String
        String[] myArr = null;
  
        // getting a element a with 
        // required condition using
        // method Find()
        Console.WriteLine("Trying to get the element from a null array");
        Console.WriteLine();
        String[] value = Array.FindAll(myArr, 
                  element => element.StartsWith("S",
                  StringComparison.Ordinal));
  
        // Display the value of the found element.
        Console.WriteLine("Elements are: ");
  
        // printing the Array of String
        PrintIndexAndValues(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();
}
}

输出：

Trying to get the element from a null array

Exception Thrown: System.ArgumentNullException

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.array.findall?view=netframework-4.7.2