SQLServer商业智能系列：MDX基础-技术开发专区

SQLServer商业智能系列：MDX基础

作者：ITPUB论坛编辑： nancy 2008-01-21 00:00

输出结果：

All elements starting from first element less than its position:
1
3
9
8
6
7
2
0

First 、FirstOrDefault、Any、All、Count 子句

注意：

101 LINQ Samples 中 First - Indexed、FirstOrDefault - Indexed、 Any - Indexed、All - Indexed、Count - Indexed 这五个例子在 Orcas Beta1中已经不在可用，即下面代码是错误的。

public void Linq60() {
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int evenNum = numbers.First((num, index) => (num % 2 == 0) && (index % 2 == 0));
Console.WriteLine("{0} is an even number at an even position within the list.", evenNum);
}
public void Linq63() {
double?[] doubles = { 1.7, 2.3, 4.1, 1.9, 2.9 };
double? num = doubles.FirstOrDefault((n, index) => (n >= index - 0.5 && n <= index + 0.5));
if (num != null)
Console.WriteLine("The value {1} is within 0.5 of its index position.", num);
else
Console.WriteLine("There is no number within 0.5 of its index position.", num);
}
public void Linq68() {
int[] numbers = { -9, -4, -8, -3, -5, -2, -1, -6, -7 };
bool negativeMatch = numbers.Any((n, index) => n == -index);
Console.WriteLine("There is a number that is the negative of its index: {0}", negativeMatch);
}
public void Linq71() {
int[] lowNumbers = { 1, 11, 3, 19, 41, 65, 19 };
int[] highNumbers = { 7, 19, 42, 22, 45, 79, 24 };
bool allLower = lowNumbers.All((num, index) => num < highNumbers[index]);
Console.WriteLine("Each number in the first list is lower than its counterpart in the second list: {0}", allLower);
}
public void Linq75() {
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int oddEvenMatches = numbers.Count((n, index) => n % 2 == index % 2);
Console.WriteLine("There are {0} numbers in the list whose odd/even status " +
"matches that of their position.", oddEvenMatches);
}

要实现这个功能，可以用Where 子句，如下：

public static void Linq60()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int evenNum = numbers.Where((num,index) =>( num % 2 == 0 && index %2 == 0) ).First();
Console.WriteLine("{0} is an even number at an even position within the list.", evenNum);
}
public static void Linq63()
{
double?[] doubles = { 1.7, 2.3, 4.1, 1.9, 2.9 };
double? num = doubles.Where((n, index) => (n >= index - 0.5 && n <= index + 0.5)).FirstOrDefault();
if (num != null)
Console.WriteLine("The value {1} is within 0.5 of its index position.", num);
else
Console.WriteLine("There is no number within 0.5 of its index position.", num);
}
public static void Linq68()
{
int[] numbers = { -9, -4, -8, -3, -5, -2, -1, -6, -7 };
bool negativeMatch = numbers.Where((n, index) => n == -index).Any();
Console.WriteLine("There is a number that is the negative of its index: {0}", negativeMatch);
}
public static void Linq71()
{
int[] lowNumbers = { 1, 11, 3, 19, 41, 65, 19 };
int[] highNumbers = { 7, 19, 42, 22, 45, 79, 24 };
bool allLower = lowNumbers.Where((num, index) => num < highNumbers[index]).All(n => true);
Console.WriteLine("Each number in the first list is lower than its counterpart in the second list: {0}", allLower);
}
public static void Linq75()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int oddEvenMatches = numbers.Where((n, index) => n % 2 == index % 2).Count();
Console.WriteLine("There are {0} numbers in the list whose odd/even status " +
"matches that of their position.", oddEvenMatches);
}

第1页：概述第2页：数组索引的例子第3页：First 、FirstOrDefault、Any、All、Count 子句

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