C＃3.0中的匿名类型等 [英] Anonymous type etc. in C# 3.0
问题描述
我理解，基本上，这个C＃3.0代码的作用，但我不清楚
如何确定lambda
表达式中num和index的数据类型在以下代码中。我也无法看到它如何将数组
索引到索引参数中？
顺便说一句：有没有更好的论坛来提出这些问题？
public void Linq12（）{
int [] numbers = {5,4,1,3,9,8,6,7,2,0};
var numsInPlace = numbers.Select（（num，index）=> new {Num = num，
InPlace =（num == index）}）;
Console.WriteLine（" Number：In-place？"）;
foreach（var n in numsInPlace）{
Console.WriteLine（" {0}：{1}"，n.Num，n.InPlace）;
}
}
Chris，
这是无效的，因为Select方法只需要一个lambda
带有一个参数的
表达式（正在评估选择的项目）。
如果你想这样做，你需要在枚举中输入一个类型
暴露了指数和价值。
希望这会有所帮助。
-
- Nicholas Paldino [.NET / C＃MVP]
- mv*@spam.guard.caspershouse.com
" Chris Dunaway" <杜****** @ gmail.com>在消息中写道
news：11 ********************** @ g49g2000cwa.googlegr oups.com ...基本上，我理解这个C＃3.0代码的作用，但是我不清楚如何在下面的代码中确定lambda
表达式中num和index的数据类型。我也无法看到它如何将数组
索引转换为索引参数？
顺便说一下：有没有更好的论坛可以提出这些问题？
public void Linq12 （）{
int [] numbers = {5,4,1,3,9,8,6,7,2,0};
var numsInPlace = numbers.Select（（ num，index）=> new {Num = num，
InPlace =（num == index）}）;
Console.WriteLine（" Number：In-place？" ）;;
foreach（var n in numsInPlace）{
Console.WriteLine（" {0}：{1}"，n.Num，n.InPlace）;
}
}
Nicholas Paldino [.NET / C＃MVP]写道：这是无效的，因为Select方法只使用一个参数（要评估的项目进行选择）的lambda
表达式。
无效？我从MS的这个链接得到了这个例子：
http://msdn.microsoft.com/vcsharp/fu...t.aspx#indexed
< blockquote>它会这样工作吗？ （注意我从lambda表达式中删除了索引参数
并在匿名
类型中使用了Array.IndexOf）
public void Linq12（）{
int [] numbers = {5,4,1,3,9,8,6,7,2,0};
var numsInPlace = numbers.Select（（num）=> new {Num = num，
InPlace =（num == Array.IndexOf（numbers，num））}）;
Console.WriteLine（" Number：In-place？"）;
foreach（var n in numsInPlace）{
Console.WriteLine（" {0}：{1}"，n.Num，n.InPlace）;
}
I understand, basically, what this C# 3.0 code does, but I am unclear
on how it determines the data type of num and index in the lambda
expression in the following code. Nor can I see how it gets the array
index into the index parameter?
BTW: Is there a better forum for asking these questions?
public void Linq12() {
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numsInPlace = numbers.Select((num, index) => new {Num = num,
InPlace = (num == index)});
Console.WriteLine("Number: In-place?");
foreach (var n in numsInPlace) {
Console.WriteLine("{0}: {1}", n.Num, n.InPlace);
}
}
Chris,
This is not valid, because the Select method will only take a lambda
expression with one parameter (the item being evaluated for selection).
If you wanted to do this, you would need a type in the enumeration which
exposed the index and the value.
Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com
"Chris Dunaway" <du******@gmail.com> wrote in message
news:11**********************@g49g2000cwa.googlegr oups.com...I understand, basically, what this C# 3.0 code does, but I am unclear
on how it determines the data type of num and index in the lambda
expression in the following code. Nor can I see how it gets the array
index into the index parameter?
BTW: Is there a better forum for asking these questions?
public void Linq12() {
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numsInPlace = numbers.Select((num, index) => new {Num = num,
InPlace = (num == index)});
Console.WriteLine("Number: In-place?");
foreach (var n in numsInPlace) {
Console.WriteLine("{0}: {1}", n.Num, n.InPlace);
}
}
Nicholas Paldino [.NET/C# MVP] wrote:This is not valid, because the Select method will only take a lambda
expression with one parameter (the item being evaluated for selection).
Not valid? I got that example from this link at MS:
http://msdn.microsoft.com/vcsharp/fu...t.aspx#indexed
Would it work like this? (Note that I eliminated the index parameter
off of the lambda expression and used of Array.IndexOf in the anonymous
type)
public void Linq12() {
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numsInPlace = numbers.Select((num) => new {Num = num,
InPlace = (num == Array.IndexOf( numbers, num ))});
Console.WriteLine("Number: In-place?");
foreach (var n in numsInPlace) {
Console.WriteLine("{0}: {1}", n.Num, n.InPlace);
}
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