Linq选择新对象

Question

我有一个linq查询

var x = (from t in types select t).GroupBy(g =>g.Type)

它按类型对对象进行分组,因此我想要包含所有分组对象及其计数的单个新对象.像这样的东西:

type1, 30    
type2, 43    
type3, 72

更清楚:分组结果应该在一个对象中,而不是每个项目类型的对象

Answer 1

阅读:LINQ中的101个LINQ示例 -来自Microsoft MSDN站点的分组操作员

var x = from t in types  group t by t.Type
         into grp    
         select new { type = grp.key, count = grp.Count() };

forsingle对象使用stringbuilder并附加它将以字典的形式执行或转换它

    // fordictionary 
  var x = (from t in types  group t by t.Type
     into grp    
     select new { type = grp.key, count = grp.Count() })
   .ToDictionary( t => t.type, t => t.count); 

   //for stringbuilder not sure for this 
  var x = from t in types  group t by t.Type
         into grp    
         select new { type = grp.key, count = grp.Count() };
  StringBuilder MyStringBuilder = new StringBuilder();

  foreach (var res in x)
  {
       //: is separator between to object
       MyStringBuilder.Append(result.Type +" , "+ result.Count + " : ");
  }
  Console.WriteLine(MyStringBuilder.ToString());   

Answer 2

所有分组对象或所有类型？听起来你可能只想要:

var query = types.GroupBy(t => t.Type)
                 .Select(g => new { Type = g.Key, Count = g.Count() });

foreach (var result in query)
{
    Console.WriteLine("{0}, {1}", result.Type, result.Count);
}

编辑:如果你想在字典中,你可以使用:

var query = types.GroupBy(t => t.Type)
                 .ToDictionary(g => g.Key, g => g.Count());

没有必要选择成对然后构建字典.

Answer 3

这里的答案让我很接近,但在2016年,我能够编写以下LINQ:

List<ObjectType> objectList = similarTypeList.Select(o =>
    new ObjectType
    {
        PropertyOne = o.PropertyOne,
        PropertyTwo = o.PropertyTwo,
        PropertyThree = o.PropertyThree
    }).ToList();