Question

class Program
{
    static void Main(string[] args)
    {
        MyDatabaseEntities entities = new MyDatabaseEntities();

        var result = from c in entities.Categories
                        join p in entities.Products on c.ID equals p.IDCategory
                        group p by c.Name into g
                        select new
                        {
                            Name = g.Key,
                            Count = g.Count()
                        };

        Console.WriteLine(result.ToString());
        Console.ReadLine();
    }
}

如何从结果集中提取值，以便我可以使用它们？

Answer 1

foreach (var item in result)
{
    var name = item.Name;
    var count = item.Count;
    ...
}

这只能在LINQ查询所在的同一方法内部工作，因为编译器只会知道LINQ new { }中使用的匿名对象类型（select）中可用的属性。

如果将LINQ查询返回给调用方法，并且想要以上面显示的方式访问它，则必须定义显式类型并在LINQ查询中使用它：

class NameCountType
{
    public string Name { get; set; }
    public int Count { get; set; }
}

...

return from ... in ...
       ...
       select new NameCountType
              {
                  Name = ...,
                  Count = ...,
              };

Answer 2

例如：

foreach (var x in result)
{
   Console.WriteLine(x.c.Name);
}

Answer 3

 var results = (from myRow in ds.Tables[0].AsEnumerable()
                  where myRow.Field<String>("UserName") == "XXX"
                  select myRow).Distinct();
 foreach (DataRow dr in results)
    UserList += " , "+dr[0].ToString();

如何从Linq查询中提取结果？

3 个答案: