LINQ 错误 : Explicit construction of entity type

Question

我在 GridView1.DataBind() 处收到此错误；

不允许在查询中显式构造实体类型“WebApplication1.MUser”。

 using (var db = new UsersDataContext())
            {
                IEnumerable<MUser> user = from u in db.MUsers
                                          where u.Id == 1
                                          select new MUser {Username = u.Username, Id = u.Id, Password=u.Password, ProjectUsers=u.ProjectUsers };

                GridView1.DataSource = user;

                GridView1.DataBind();

            }

如何解决这个问题？

我正在关注本教程
http://weblogs.asp.net/scottgu/archive/2007/04/21/new-orcas-language-feature-query-syntax.aspx

Answer 1

如果要返回完整的 Muser 对象，只需使用:

using (var db = new UsersDataContext())
        {
            IEnumerable<MUser> user = from u in db.MUsers
                                      where u.Id == 1
                                      select u;

            GridView1.DataSource = user;

            GridView1.DataBind();

        }

或者，如果您想返回用户的自定义部分(即仅来自 Muser 对象的某些属性)，您可以使用匿名类型，如下所示。

using (var db = new UsersDataContext())
        {
            IEnumerable<MUser> user = from u in db.MUsers
                                      where u.Id == 1
                                      select new  {Username = u.Username, Id = u.Id, Password=u.Password, ProjectUsers=u.ProjectUsers };

            GridView1.DataSource = user;

            GridView1.DataBind();

        }