Csharp/CSharp Tutorial/LINQ/LastOrDefault — различия между версиями

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м (1 версия)
 
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Версия 15:31, 26 мая 2010

Call LastOrDefault returned from Take

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {
        string[] presidents = {"G", "H", "a", "H", "over", "Jack"};
        string name = presidents.Take(0).LastOrDefault();
        Console.WriteLine(name == null ? "NULL" : name);
    }
}

LastOrDefault returns null when an Element Is Found

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {
        string[] presidents = {"G", "H", "a", "H", "over", "Jack"};
        string name = presidents.LastOrDefault();
        Console.WriteLine(name == null ? "NULL" : name);
    }
}

LastOrDefault with string operator

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
    public static void Main() {
        string[] presidents = {"G", "H", "a", "H", "over", "Jack"};
        string name = presidents.LastOrDefault(p => p.StartsWith("Z"));
        Console.WriteLine(name == null ? "NULL" : name);
    }
}

Use LastOrDefault

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
public class MainClass{
   public static void Main(){
            int[] numbers = { 1, 3, 5, 7, 9 };
            var query = numbers.FirstOrDefault(n => n % 2 == 0);
            Console.WriteLine("The first even element in the sequence");
            Console.Write(query);
            Console.WriteLine("The last odd element in the sequence");
            query = numbers.LastOrDefault(n => n % 2 == 1);
            Console.Write(query);
   }
}