Question

给出以下代码：

string[]  colors = {"red","green","blue","red","green","blue"};
var distinctColors = (from c in colors select c).Distinct();
distinctColors.Dump();

是否可以将调用.Distinct()折叠为嵌入式查询语法？

类似于int T-SQL

select distinct color from TableofColors

Answer 1

C＃的查询表达式语法不包含“distinct”。然而，VB的确如此 - 例如，来自MSDN docs for VB's Distinct clause：

// VB
Dim customerOrders = From cust In customers, ord In orders _
                     Where cust.CustomerID = ord.CustomerID _
                     Select cust.CompanyName, ord.OrderDate _
                     Distinct

C＃等效项必须以点表示法显式调用Distinct()。

但是，您的示例仍然可以简化：

string[]  colors = {"red","green","blue","red","green","blue"};
var distinctColors = colors.Distinct();
distinctColors.Dump();

不要认为使用查询表达式来使用LINQ：）

Answer 2

据我所知，C＃中没有明显的嵌入式查询语法。这很接近：

var distinctColors = (from color in colors
                      select color).Distinct()

Answer 3

查询理解语法不支持Distinct方法。

在你的情况下，你可以简单地写colors.Distinct();你没有对查询表达式做任何事情。

Answer 4

你可以试试这个

var dis = from c in colors
   group c by c;

foreach (var cVal in dis)
   {
      string s = cVal.Key;
   }

可以使用所谓的嵌入式查询而不是方法调用来表达

4 个答案: