.Net 4.0 无法将类型 'System.Collections.Generic.List`1[ClassName]' 的对象转换为类型 'ClassName'

Question

public class SkillView {
public string Name { get; set; } 
public IList<SkillValueView> Selected { get; set; }}

public class SkillValueView {
    public string APlan { get; set; }
    public DateTime? DueDate { get; set; }}

private IList<SkillValueView> MapToSkillValueList(IGrouping<string, GetSession_Result> query)
    {
        var actionItem = query.FirstOrDefault();
        List<SkillValueView> LSVV = new List<SkillValueView>();
        SkillValueView SVV = new SkillValueView();

        for (int i = 0; i < actionItem.NoOf; i++)
            {
                SVV.APlan = actionItem.ExAPlan;
                SVV.DueDate = actionItem.ExDueDate;
                LSVV.Add(new SkillValueView() { APlan = SVV.APlan, DueDate = SVV.DueDate });
            }
        }
        return LSVV;
    }

private SkillView MapToSkill(IGrouping<int, GetSession_Result> query){
    var skill = query.FirstOrDefault();
    return new SkillView()
        {
            Name = skill.SkillName,
            Selected = query.GroupBy(s => s.ExAPlan).Select(MapToSkillValueList).ToList()
        }; 
}

我无法映射 >Selected = query.GroupBy(s => s.ExAPlan).Select(MapToSkillValueList).ToList () 并出现错误 无法将类型 'System.Collections.Generic.List`1[IsaiX.Coach.Models.SkillValueView]' 的对象转换为类型 'IsaiX.Coach.Models.SkillValueView'。

Answer 1

在这种情况下，您应该使用 SelectMany 而不是 Select。

query.GroupBy(s => s.ExAPlan).SelectMany(MapToSkillValueList).ToList().

Projects each element of a sequence to an IEnumerable and flattens the resulting sequences into one sequence

.Net 4.0 无法将类型 'System.Collections.Generic.List`1[ClassName]' 的对象转换为类型 'ClassName'

.Net 4.0 Unable to cast object of type 'System.Collections.Generic.List`1[ClassName]' to type 'ClassName'

c#

.net

linq

lambda

c#-4.0