c# - 无法转换类型为 'System.Linq.GroupedEnumerable to type ' System.Collections.Generic.List 的对象

Question

我有这样的类(class)。

 public static SkillViewModel GetAllList(string ID)
{
    ListViewModel viewModel = new ListViewModel();
    DataTable dt = DAL.GetAllList(ID);

    List<Skill> skills = new List<Skill>();
    foreach (DataRow row in dt.Rows)
    {
        Skill skill = new Skill() { GroupName = row["GroupName"] != null ? row["GroupName"].ToString() : string.Empty, SubName = row["SubName"] != null ? row["SubName"].ToString() : string.Empty};
        skills.Add(skill);
    }
    viewModel.skills = skills;
    viewModel.skills = skills.GroupBy(x => x.GroupName);  //Showing error in this line
   return viewModel;

}

还有一个是这样的:

 public class SkillViewModel
  {
    public List<Skill> skills { get; set; }
  }

  public class Skill
{
    [DisplayName("Sub Name")]
    [Required]
    public string SubName { get; set; }

    [DisplayName("Group Name")]
    [Required]
    public string GroupName { get; set; }
}

但是它通过说

失败了

Error: Cannot implicitly convert type 'System.Collections.Generic.IEnumerable>' to 'System.Collections.Generic.List'. An explicit conversion exists (are you missing a cast?)

请帮助。提前致谢。

Answer 1

只需添加 ToList与 SelectMany在语句的末尾，如:

viewModel.skills = skills.GroupBy(x => x.GroupName).SelectMany(r => r).ToList();

使用 SelectMany会使组变平，不确定为什么要对数据进行分组，而您的属性是 List<Skill>