本文整理汇总了C#中System.Linq.Queryable.LastOrDefault方法的典型用法代码示例。如果您正苦于以下问题：C# Queryable.LastOrDefault方法的具体用法？C# Queryable.LastOrDefault怎么用？C# Queryable.LastOrDefault使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。
在下文中一共展示了Queryable.LastOrDefault方法的4个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的C#代码示例。
示例1:
double[] numbers = { 49.6, 52.3, 51.0, 49.4, 50.2, 48.3 };
// Get the last number in the array that rounds to 50.0,
// or else the default value for type double (0.0).
double last50 =
numbers.AsQueryable().LastOrDefault(n => Math.Round(n) == 50.0);
Console.WriteLine("The last number that rounds to 50 is {0}.", last50);
// Get the last number in the array that rounds to 40.0,
// or else the default value for type double (0.0).
double last40 =
numbers.AsQueryable().LastOrDefault(n => Math.Round(n) == 40.0);
Console.WriteLine(
"The last number that rounds to 40 is {0}.",
last40 == 0.0 ? "[DOES NOT EXIST]" : last40.ToString());输出：
The last number that rounds to 50 is 50.2.
The last number that rounds to 40 is [DOES NOT EXIST].
示例2:
// Create an empty array.
string[] fruits = { };
// Get the last item in the array, or else the default
// value for type string (null).
string last = fruits.AsQueryable().LastOrDefault();
Console.WriteLine(
String.IsNullOrEmpty(last) ? "[STRING IS NULL OR EMPTY]" : last);输出：
[STRING IS NULL OR EMPTY]
示例3:
List<int> daysOfMonth = new List<int> { };
// Setting the default value to 1 after the query.
int lastDay1 = daysOfMonth.AsQueryable().LastOrDefault();
if (lastDay1 == 0)
{
lastDay1 = 1;
}
Console.WriteLine("The value of the lastDay1 variable is {0}", lastDay1);
// Setting the default value to 1 by using DefaultIfEmpty() in the query.
int lastDay2 = daysOfMonth.AsQueryable().DefaultIfEmpty(1).Last();
Console.WriteLine("The value of the lastDay2 variable is {0}", lastDay2);输出：
The value of the lastDay1 variable is 1 The value of the lastDay2 variable is 1
示例4: Queryable.LastOrDefault(filter)
//引入命名空间
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);
}
}