動態撰寫LINQ表達式

Question

是否可以動態地結合表達式：

from c in collection where c.Property == true select c 

與表達

from result in results 
group result by result.Property 
into g 
select new g.Key 

其中「結果」應該是集合從第一表達式返回？

我將使用由表達式從分貝使用NHibernate獲取數據，所以我想聯合表達爲等於我是否寫爲

from c in collection 
where c.Property == true 
group c by c.Property 
into g 
select new g.Key 

表達式是在所定義的等級：

public class MyClass : MyAbstractClass<User> 
{ 
    public MyClass() 
    { 
     FirstExpression = users => from user in users where ... select user;    

     SecondExpression = results => from result in results 
         group result by result.Property into g 
         select g.Key 

    } 
} 

Answer 1

是的，這是可能的。只需將第一個查詢到results變量的結果，而不枚舉它：

var results = from c in collection where c.Property == true select c; 

from result in results 
group result by result.Property 
into g 
select g.Key; 

順便說一句，你的第二個查詢是一個簡單的distinct：

results.Distinct(r => r.Property); 

Answer 2

var query = collection; 

if (condition) 
    query = query.Where(c => c.Property); 

var result = query.GroupBy(c => c.Property).Select(g => g.Key);