函数编程和LINQ [英] Functional programming and LINQ

问题描述

目前我正在阅读CodeProject的优秀文章之一

我遇到了以下代码行的麻烦：



< pre lang =C＃> string [] names = new string [] { test1， test2};

Predicate< string> longWords = 委托（字符串字）{ return word.Length > 4 ; };
int numberOfBooksWithLongNames = names.Count（longWords）;

编译器错误CS1928和CS1503在最后一行。



这是我的石器时代C＃编译器（VS2010）还是出了什么问题？



提前谢谢

解决方案

将 Predicate< string> 更改为 Func< string，bool> 。

Linq 方法计数定义为;

public static int Count< TSource>（此IEnumerable< TSource>源，Func< TSource，bool>谓词）;



希望这会有所帮助，

Fredrik

At the moment I am reading one of the excellent articles of CodeProject
and I have troubles with code lines like:

string[] names = new string[] {"test1", "test2"};

Predicate<string> longWords = delegate(string word) { return word.Length > 4; };
int numberOfBooksWithLongNames = names.Count(longWords);

Compiler errors CS1928 and CS1503 in the last line.

Is it my stone-age C# compiler (VS2010) or what is going wrong?

Thanks in advance

解决方案

Change Predicate<string> to Func<string, bool>.
The Linq method Count is defined as;
public static int Count<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate);

Hope this helps,
Fredrik

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