C# 带有实体框架的 Linq
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Linq with entity framework
提问by razeth01
I'm new to LINQ and Entity Framework and would appreciate some advice on the following scenario.
我是 LINQ 和实体框架的新手，希望得到有关以下场景的一些建议。
I have a entity model with two tables.
我有一个带有两个表的实体模型。
Travel_Request and Resource
Travel_Request 和资源
Sample Fields
示例字段
Travel_Request
Travel_Request
Request_ID
Resource_ID
Resource
资源
Resource_ID
Resource_Name
I would like to add the Resource_Name to the list when returning all the TRAVEL_REQUESTS
我想在返回所有 TRAVEL_REQUESTS 时将 Resource_Name 添加到列表中
Thanks in advance
提前致谢
采纳答案by Fabien
Hi you need to use the Linq join:
您好，您需要使用 Linq 连接：
var data = from t in Travel_Request
join r in Resource on t.Resource_ID equals r.Resource_ID
select new
{
RequestId = t.Request_ID,
ResourceId = t.Resource_ID,
ResourceName = r.Resource_Name
};
If you already have an EF association then it could simply be:
如果您已经有一个 EF 关联，那么它可能只是：
var data = from t in Travel_Request
select new
{
RequestId = t.Request_ID,
ResourceId = t.Resource_ID,
ResourceName = t.Resource.Resource_Name
};
回答by Rob White
You will have to create a new object something like this.
您将不得不创建一个类似这样的新对象。
var data = Travel_Request.Select(s=> new { Resource_Name = s.Recource.Resource_Name, Request_ID = s.Request_ID, Resource_ID = s.Resource_ID}).ToList();
As long as I've understood the question correctly this will work.
只要我正确理解了这个问题，这就会起作用。
回答by Thilina H
You can query Travel_Request entity and use the navigation propety to do that.
您可以查询 Travel_Request 实体并使用导航属性来执行此操作。
var resultList = DbContext.Travel_Request.Resources.where(x=>x.Resource_Name =="Your string").ToList();
回答by Michael90
Use the Join:
使用连接：
Travel_Request.Join(Resource, tr => tr.ResourceId, r => r.ResourceId, (tr, r) => new { RequestId = tr.RequestId, ResourceId = tr.ResourceId, Name = r.ResourceName})
Or what a better practice would be is adding a Navigation property to TravelRequest. TravelRequest would look like this:
或者更好的做法是向 TravelRequest 添加 Navigation 属性。TravelRequest 看起来像这样：
int RequestId { get; set; }
int ResourceId{ get; set; }
[ForeignKey("ResourceId")]
Resource Resource { get; set; }
This way you can use Include
这样你就可以使用 Include
DBContext.TravelRequests.Include("Resource").First().Resource.Name;
Include tells EF to get the Resource with the TravelerRequest
Include 告诉 EF 使用 TravelerRequest 获取资源
回答by Ryan Schlueter
I would add a model that has all three then do something like.
我会添加一个包含所有三个的模型然后做类似的事情。
var TravelRequests =
from p in Travel_Request
from r in Resource.where(Res => Res.Resource_ID == p.Resource_ID)
select new TravelModel{
requestID = p.requestID,
Resource_ID = p.Resource_ID,
ResourceName = r.ResourceName
};
But thats just an example of how I would do it and there might be better ways. Also syntax might be a little off but general idea is there.
但这只是我将如何做的一个例子，可能有更好的方法。语法也可能有点偏差，但总体思路是存在的。
