LINQ查询空引用异常 [英] LINQ query null reference exception

问题描述

我有下一个查询：

  var bPermisos = from b in ruc.Permisos
                      where b.IdUsuario == cu.Id
                          select new Permisos(){
                              Id=b.Id,
                              IdUsuario=b.Id,
                              IdPerfil=b.Id,
                              Estatus=b.Estatus
                          };
  var qSisPer = from perm in bPermisos
                      **select new {                    
                          perm.IdPerfil,
                          perm.Cat_Perfil.Nivel,
                          perm.Cat_Perfil.Nombre,   
                          Nombre_Sistem=perm.Cat_Perfil.Cat_Sistema.Nombre**
                      };

并且正在抛出一个异常，请帮助！

And is throwing me an exception, plz help!

推荐答案

对于初学者，我认为第一个查询可能可能被重写为：

For starters, I think the first query can probably be rewritten as:

var bPermisos = ruc.Permisos.Where(b => b.IdUsuario == cu.Id);

除此之外，您的代码正在做什么还不清楚您似乎正在重新投影您已有的结果 - 使用已知类型的项目并创建匿名类型来保存它们。此外，第二个投影正在访问在第一个查询中未选择的一群成员。

Beyond that, it is rather unclear what your code is doing. You appear to be re-projecting the results you already have -- taking items of a known type and creating an anonymous type to hold them. Furthermore, the second projection is accessing a bunch of members that were not selected in the first query.

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