Can I streamline this LINQ query

I am learning LINQ and I want to know if it is possible to streamline the following LINQ query...

Right now I have two strings and I parse the concatenated string to count the use of each word. I want to know is it possible to keep one LINQ expression but not have to replicate the string.Concat section in the from and let expressions.

        string sentence = "this is the first sentence";
        string sentence2 = "this is the second sentence";

        var res = from word in string.Concat(sentence, sentence2).Split()
                  开发者_C百科let combinedwords = string.Concat(sentence, sentence2).Split()
                  select new { TheWord = word, Occurance = combinedwords.Count(x => x.Equals(word)) };

Your query returns a slightly bizarre resultset:

TheWord         Occurrence
this            1
is              2
the             2
first           1
sentencethis    1
is              2
the             2
second          1
sentence        1

Is that what you want, or would you you prefer the results to be more like this?

TheWord         Occurrence
this            2
is              2
the             2
first           1
sentence        2
second          1

To get these results you can do something like this:

var res = from word in sentence.Split()
                               .Concat(sentence2.Split())
          group word by word into g
          select new { TheWord = g.Key, Occurrence = g.Count() };

Another option; better (theoretical) performance but less readable:

var res = sentence.Split()
                  .Concat(sentence2.Split())
                  .Aggregate(new Dictionary<string, int>(),
                             (a, x) => {
                                           int count;
                                           a.TryGetValue(x, out count);
                                           a[x] = count + 1;
                                           return a;
                                       },
                             a => a.Select(x => new {
                                                        TheWord = x.Key,
                                                        Occurrence = x.Value
                                                    }));