LINQ查询表达式---------where子句
where 子句用在查询表达式中，用于指定将在查询表达式中返回数据源中的哪些元素。 它将一个布尔条件（“谓词”）应用于每个源元素（由范围变量引用），并返回满足指定条件的元素。 一个查询表达式可以包含多个 where 子句，一个子句可以包含多个谓词子表达式。
1.1 常见的where子句查询
static void Main(string[] args)
{
int[] numbers = { , , , , , , , , , };
var num1 = from n in numbers
where n >
select n;
foreach (var i in num1)
{
Console.Write(i + " ");
}
Console.Write("\n");
Console.WriteLine("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
var num2 = from n in numbers
where n >
where n % ==
select n;
foreach (var i in num2)
{
Console.Write(i + " ");
}
Console.Write("\n");
Console.WriteLine("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
var num3 = from n in numbers
where n > && n <
select n;
foreach (var i in num3)
{
Console.Write(i + " ");
}
Console.Write("\n");
Console.WriteLine("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
var num4 = from n in numbers
where (n == || n < ) && (n != )
select n;
foreach (var i in num4)
{
Console.Write(i + " ");
}
Console.ReadLine();
}
输出结果：
9 7 8 6
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
8 6
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7 8 6
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
5 8 3 4 6 2 1 0
1.2 在where子句中用自定义函数
static void Main(string[] args)
{
int[] numbers = { , , , , , , , , , };
var num = from n in numbers
where IsEva(n)
select n;
foreach (var i in num)
{
Console.Write(i + " ");
}
Console.ReadLine();
}
public static bool IsEva(int i)
{
if (i % == )
return true;
else
return false;
}
1.3 动态微词的筛选
static void Main(string[] args)
{
int[] numbers = { , , , , , , , , , };
//定义动态的谓词数组，这个数组应该由实际运行环境生成
int[] number = { , , , , };
//查询在给定谓词数组里不存在的数字
var num = from n in numbers
where !number.Contains(n)
select n;
foreach (var i in num)
{
Console.Write(i + " ");
}
Console.ReadLine();
}