MVC 4和Entity Framework表加入

问题描述：

此产品是推动我疯了;-) 我试图做一个简单的查询，将两个表MVC 4和Entity Framework表加入

我有以下几点：

仓储类方法

public IQueryable<ADPerson> FindAll(string UserId) 
    { 
     return (from p in db.ADPerson 
       select p); 


    }

在我的控制器：

var ADPersonList = from o in ADPersonDB.FindAll(GetUserId()) 
        join c in MSDNTypeDB.FindAll(GetUserId()) on o.MsdnTypeId equals c.MsdnTypeId 
        select new ADPerson() 
        { 

         AdPersonId = o.AdPersonId, 
         SamAccountName = o.SamAccountName, 
         Description = o.Description, 
         DisplayName = o.DisplayName, 
         UserPrincipalName = o.UserPrincipalName, 
         Enabled = o.Enabled, 
         LastUpdated = o.LastUpdated, 
         OnlineAssetTag = o.OnlineAssetTag, 
         MsdnTypeId = o.MsdnTypeId, 
         MsdnSubscription = c.MsdnTypeDescription, 


        };

我不断收到一封RROR：

{"The specified LINQ expression contains references to queries that are associated with different contexts."}

我也尝试添加到存储库类：

仓储类方法

public IQueryable<ADPerson> FindAll(string UserId) 
    { 
     //return (from p in db.ADPerson 
     //  select p); 

     var query = from o in db.ADPerson 
        join c in db.MsdnTypes on o.MsdnTypeId equals c.MsdnTypeId 
        select new ADPerson() 
        { 

         AdPersonId = o.AdPersonId, 
         SamAccountName = o.SamAccountName, 
         Description = o.Description, 
         DisplayName = o.DisplayName, 
         UserPrincipalName = o.UserPrincipalName, 
         Enabled = o.Enabled, 
         LastUpdated = o.LastUpdated, 
         OnlineAssetTag = o.OnlineAssetTag, 
         MsdnTypeId = o.MsdnTypeId, 

         MsdnSubscription = c.MsdnTypeDescription, 


        }; 

     return query; 

    }

真的就那么难做到两个表之间的简单连接，并填充变量实体框架

谢谢

是否使用第二种方法同样的错误？ – mattytommo 2013-03-14 18:04:20

优秀点：否第二个返回的错误是：实体或复杂类型'project.Models.ADPerson'不能在LINQ to Entities查询中构造。 – 2013-03-14 18:06:22

RE：第二个错误。那是因为你不能*投影到映射的实体上。您可以将查询投影到匿名对象，然后将其映射到ADPerson实体 – 2013-03-14 18:09:27

答

项目到一个匿名对象

var query = from o in db.ADPerson 
    join c in db.MsdnTypes on o.MsdnTypeId equals c.MsdnTypeId 
    select new 
    { 
    AdPersonId  = o.AdPersonId, 
    SamAccountName = o.SamAccountName, 
    Description  = o.Description, 
    DisplayName  = o.DisplayName, 
    UserPrincipalName = o.UserPrincipalName, 
    Enabled   = o.Enabled, 
    LastUpdated  = o.LastUpdated, 
    OnlineAssetTag = o.OnlineAssetTag, 
    MsdnTypeId  = o.MsdnTypeId, 
    MsdnSubscription = c.MsdnTypeDescription, 
    };

然后映射回你的实体

foreach (var item in query) 
{ 
    var adPerson = new ADPerson 
    { 
    AdPersonId   = item.AdPersonId, 
    SamAccountName  = item.SamAccountName, 
    Description  = item.Description, 
    DisplayName  = item.DisplayName, 
    UserPrincipalName = item.UserPrincipalName, 
    Enabled   = item.Enabled, 
    LastUpdated  = item.LastUpdated, 
    OnlineAssetTag  = item.OnlineAssetTag, 
    MsdnTypeId   = item.MsdnTypeId, 
    MsdnSubscription = item.MsdnTypeDescription, 
    { 
}

第一个var查询失败是否有假设选择新？ – 2013-03-14 19:50:46

@DavidCostelloe是的，对不起。编辑回答 – 2013-03-14 19:52:50

获取错误“无效的列名'MsdnSubscription”字段 – 2013-03-14 20:50:18

答

public IQueryable<ADPerson> FindAll(string UserId) 
    { 
     // return (from p in db.ADPerson 
     //  select p); 
     List<ADPerson> lst = new List<ADPerson>(); 
     var query = from o in db.ADPerson 
        join c in db.MsdnTypes on o.MsdnTypeId equals c.MsdnTypeId 
        select new 
         { 

          AdPersonId = o.AdPersonId, 
          SamAccountName = o.SamAccountName, 
          Description = o.Description, 
          DisplayName = o.DisplayName, 
          UserPrincipalName = o.UserPrincipalName, 
          Enabled = o.Enabled, 
          LastUpdated = o.LastUpdated, 
          OnlineAssetTag = o.OnlineAssetTag, 
          MsdnTypeId = o.MsdnTypeId, 
          MsdnSubscription = c.MsdnTypeDescription 

         }; 
     foreach (var item in query) 
     { 
      var adPerson = new ADPerson() 
       { 
        AdPersonId = item.AdPersonId, 
        SamAccountName = item.SamAccountName, 
        Description = item.Description, 
        DisplayName = item.DisplayName, 
        UserPrincipalName = item.UserPrincipalName, 
        Enabled = item.Enabled, 
        LastUpdated = item.LastUpdated, 
        OnlineAssetTag = item.OnlineAssetTag, 
        MsdnTypeId = item.MsdnTypeId, 
        MsdnSubscription = item.MsdnSubscription 
       }; 
      lst.Add(adPerson); 

     } 

     return lst.AsQueryable(); 



    }

它可能是你有一个尾随逗号在“MsdnSubscription = c.MsdnTypeDescription”，也在第二个 – eburgos 2013-03-14 20:11:07

谢谢发现它是支柱{和};几乎在那里:-) – 2013-03-14 20:32:25

MVC 4和Entity Framework表加入

相关推荐