如何在LINQ中执行此查询

Question

考虑这个简短的片段:

var candidateWords = GetScrabblePossibilities(letters);
var possibleWords = new List<String>();
foreach (var word in candidateWords)
{
    if (word.Length == pattern.Length)
    {
        bool goodMatch = true;
        for (int i=0; i < pattern.Length && goodMatch; i++)
        {
            var c = pattern[i];
            if (c!='_' && word[i]!=c)
                goodMatch = false;
        }
        if (goodMatch)
            possibleWords.Add(word);
    }
}

是否有一种方法来表达这干净使用LINQ?
这是什么?

Answer 1

一种简单的翻译是使用Zip运算符将每个候选词覆盖在模式词上。

var possibleWords = from word in candidateWords
                    where word.Length == pattern.Length
                       && word.Zip(pattern, (wc, pc) => pc == '_' || wc == pc)
                              .All(match => match)
                    select word;

如果你真的想关注索引，你可以使用Range操作符:

var possibleWords = from word in candidateWords
                    where word.Length == pattern.Length
                       && Enumerable.Range(0, word.Length)
                                    .All(i => pattern[i] == '_' 
                                           || pattern[i] == word[i])
                    select word;

编辑:

正如David Neale指出的，Zip操作符在。net 4.0之前是不可用的。但是，自己实现它是微不足道的。

Answer 2

另一种方法:

var possibleWords = candidateWords.Where(w => w.Length == pattern.Length && 
                                         word.Select((c, i) => pattern[i] == '_' || 
                                                               pattern[i] == c)
                                             .All(b => b))
                                  .ToList();