Question

有没有更好的方法来编写以下方法？使用LINQ可能吗？而不是声明一个新列表，然后使用foreach来填充列表，有没有更好的方法可以使用LINQ在一行中执行此操作？

public IEnumerable<RoleAreasModel> GetRolesWithRoleAreasModelByUserGUID(Guid guid)
    {
      IList<RoleAreasModel> rolesWithRoleAreas = new List<RoleAreasModel>();
      foreach (AspnetRolesRecord role in GetByUserGUID(guid))
      {
        RoleAreasRecord roleAreaRecord = RoleAreasService.Instance.GetRecord(RoleAreasRecord.Fields.ID, role.ID);
        rolesWithRoleAreas.Add(new RoleAreasModel(roleAreaRecord.Area, new RolesMapper().MapToModel(role), getAreaControllersData(roleAreaRecord.ID)));
      }
      return rolesWithRoleAreas;
    }

Answer 1

由于您返回IEnumerable<RoleAreasModel>，为什么不使用yield return而不是创建临时列表？

public IEnumerable<RoleAreasModel> GetRolesWithRoleAreasModelByUserGUID(Guid guid)
{
    foreach (AspnetRolesRecord role in GetByUserGUID(guid))
    {
        RoleAreasRecord roleAreaRecord = RoleAreasService.Instance.GetRecord(RoleAreasRecord.Fields.ID, role.ID);
        yield return new RoleAreasModel(roleAreaRecord.Area, new RolesMapper().MapToModel(role), getAreaControllersData(roleAreaRecord.ID));
    }
}

顺便说一下，Eric Lippert写了一篇非常有趣的关于迭代器的博客文章以及它们如何在C＃中工作。非常值得一读

http://blogs.msdn.com/b/ericlippert/archive/2009/07/09/iterator-blocks-part-one.aspx

http://blogs.msdn.com/b/ericlippert/archive/tags/iterators/

Answer 2

public IEnumerable<RoleAreasModel> Foo(Guid id)
{
   var mapper = new RolesMapper();
   return from role in GetByUserGUID(id)
          let areaRecord = RoleAreasService.Instance.GetRecord(RoleAreasRecord.Fields.ID, role.ID)
          select new RoleAreasModel(areaRecord.Area, mapper.MapToModel(role), getAreaControllersData(areaRecord.ID));
}

希望它有所帮助。

Answer 3

这个怎么样？

public IEnumerable<RoleAreasModel> GetRolesWithRoleAreasModelByUserGUID(Guid guid)
{
  return GetByUserGUID(guid).Select( role => 
    {
      var roleAreaRecord = RoleAreasService.Instance.GetRecord(RoleAreasRecord.Fields.ID, role.ID);
      return new RoleAreasModel(roleAreaRecord.Area, new RolesMapper().MapToModel(role),getAreaControllersData(roleAreaRecord.ID)));
    });
}

使用LINQ改进方法

3 个答案: