[英]return LINQ query to view and loop through the results in the view
I am running in to a problem where I have made the following query in my controller: 我遇到了一个问题,我在我的控制器中进行了以下查询:
var query = from pmt in db.ProjectHasTags
join project in db.Projects on pmt.ProjectId equals project.ID
join tag in db.ProjectTags
on pmt.TagId equals tag.ID
group pmt by pmt.Project into pmtGroup
select new
{
Project = pmtGroup.Key,
Tags = pmtGroup.Select(project => project.ProjectTag)
};
I want to return this query to a view using: 我想使用以下命令将此查询返回到视图:
return View(query.ToList());
In the view file I have the following code: 在视图文件中,我有以下代码:
@model IEnumerable<portfolio.Models.ProjectHasTag>
@foreach (var p in Model)
{
@p.Project.Title
foreach (var tag in p.Tags)
{
@tag.title
}
}
I get the following error: 我收到以下错误:
The model item passed into the dictionary is of type 'System.Collections.Generic.List
1[<>f__AnonymousType6
2[portfolio.Models.Project,System.Collections.Generic.IEnumerable1[portfolio.Models.ProjectTag]]]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable
1[portfolio.Models.ProjectHasTag]'.传递到字典中的模型项的类型为'System.Collections.Generic.List
1[<>f__AnonymousType6
2 [portfolio.Models.Project,System.Collections.Generic.IEnumerable1[portfolio.Models.ProjectTag]]]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable
1 [portfolio.Models.ProjectHasTag]'1[portfolio.Models.ProjectTag]]]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable
。
The ProjectHasTag model code: ProjectHasTag模型代码:
public class ProjectHasTag
{
public int ID { get; set; }
public int? ProjectId { get; set; }
[ForeignKey("ProjectId")]
[DisplayName("Project")]
public virtual Project Project { get; set; }
public int? TagId { get; set; }
[ForeignKey("TagId")]
[DisplayName("Tag")]
public virtual ProjectTag ProjectTag { get; set; }
public virtual ICollection<ProjectTag> Tags { get; set; }
}
This is what I want to achieve: http://i.stack.imgur.com/DAZ5n.png (I cant post images yet) 这就是我想要实现的目的: http : //i.stack.imgur.com/DAZ5n.png (我无法发布图片)
thanks for taking the time, English is not my first language. 感谢花时间,英语不是我的第一语言。
The problem is this part of your query: 问题是这部分查询:
select new
{
Project = pmtGroup.Key,
Tags = pmtGroup.Select(project => project.ProjectTag)
};
You're not specifying the type that should be instantiated, so it's creating an anonymous type, which is then being passed to your view. 您没有指定应该实例化的类型,因此它创建了一个匿名类型,然后将其传递给您的视图。 You probably want something like this:
你可能想要这样的东西:
select new ProjectHasTag
{
Project = pmtGroup.Key,
Tags = pmtGroup.Select(project => project.ProjectTag)
};
Update 更新
Just as the error is telling you, ProjectHasTag
does not have a Tags
property. 就像错误告诉你的那样,
ProjectHasTag
没有Tags
属性。 It looks like what you want is really this: 它看起来像你想要的是这样的:
select new ProjectHasTag
{
Project = pmtGroup.Key,
ProjectTag = pmtGroup.Select(project => project.ProjectTag)
};
However, it's a little unclear what you're trying to do because in your view it looks as though you have multiple tags for each project, in which case it should really be a collection. 但是,你有点不清楚你想要做什么,因为在你的视图中看起来好像你有每个项目的多个标签,在这种情况下它应该真的是一个集合。 Something like:
就像是:
public virtual ICollection<ProjectTag> Tags { get; set; }
Update Two 更新二
I forgot the Entity Framework (EF) is picky when it comes to directly instantiating entity types. 我忘了实体框架(EF)在直接实例化实体类型时很挑剔。 For a quick fix, you should be able to map from an anonymous type to the entity type (as described here ).
为了速战速决,你应该能够从一个匿名类型的实体类型映射(如描述在这里 )。
However, EF doing this is actually a good thing because it's forcing you to adopt a design strategy that will allow you to leverage more power from MVC. 然而,EF这样做实际上是一件好事,因为它迫使你采用一种设计策略,让你可以利用MVC的更多功能。 In particular, this would be a good time to learn about ViewModels (see: ASP.NET MVC - How exactly to use View Models and http://geekswithblogs.net/michelotti/archive/2009/10/25/asp.net-mvc-view-model-patterns.aspx ).
特别是,这将是了解ViewModel的好时机(请参阅: ASP.NET MVC - 如何使用View Models和http://geekswithblogs.net/michelotti/archive/2009/10/25/asp.net- mvc-view-model-patterns.aspx )。
In the select part of your query, you create an anonymous object, and your model requires objects form type ProjectHasTag
. 在查询的选择部分中,您将创建一个匿名对象,并且您的模型需要表单类型为
ProjectHasTag
对象。 So this should look like (look at the select new ProjectHasTag
): 所以这应该是这样的(看看
select new ProjectHasTag
):
var query = from pmt in db.ProjectHasTags
join project in db.Projects on pmt.ProjectId equals project.ID
join tag in db.ProjectTags
on pmt.TagId equals tag.ID
group pmt by pmt.Project into pmtGroup
select new ProjectHasTag
{
Project = pmtGroup.Key,
Tags = pmtGroup.Select(project => project.ProjectTag)
};
Since you have an ICollection , you are telling Linq, that you want your ProjectTags to be lazy loaded. 由于你有一个ICollection,你告诉Linq,你希望你的ProjectTag是延迟加载的。 Like @John H said above, since you have added the Tags property to your ProjectHasTag class, you can populate it such:
就像上面提到的@John H一样,既然你已经将Tags属性添加到了ProjectHasTag类中,你就可以填充它:
select new ProjectHasTag
{
Project = pmtGroup.Key,
Tags = pmtGroup.Select(project => project.ProjectTag)
};
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