将 lambda 表达式转换为 Json [英] Convert lambda expression to Json

问题描述

首先请确保 stackoverflow 上的所有解决方案都没有解决我的问题(可能是由 Entity Framework 6 引起的).我有 3 个实体:Student、City 和 Region，如下所示:

First of all please be sure that none of the solution on stackoverflow has not solved my problem (maybe it is caused from Entity Framework 6). I have 3 entities: Student, City and Region as below:

实体:

public class Student
{
    public int ID { get; set; }

    public string Course { get; set; }  

    public int CityID { get; set; }

    public virtual City City { get; set; }
}


public class City
{
    public int ID { get; set; }        

    public string Name { get; set; }

    public int RegionID { get; set; }

    public virtual Region Region { get; set; }

    public virtual ICollection<Student> Students { get; set; }    
}


public class Region
{
    public int ID { get; set; }

    public string Name { get; set; }

    public virtual ICollection<City> Cities { get; set; } 
}

控制器:

public ActionResult Index_Read([DataSourceRequest] DataSourceRequest request)
    {
        var dataContext = repository.Students;
        var students = dataContext.ToDataSourceResult(request, m => new 
        {
            ID = m.ID,
            Course = m.Course,

            City = m.City.Name, //I can get City name and show it in View.
            MyRegionName = m.City.Region.Name //I can get region name and assign it to 
//"MyRegionName" parameter in JSON. However in View I cannot get it using "MyRegionName" paremeter  
        });           

        return Json(students, JsonRequestBehavior.AllowGet);
    }

查看:

@model IEnumerable<Student>


@(Html.Kendo().Grid<Student>()
    .Name("Grid")
    .Columns(columns =>
    {
        columns.Bound(m => m.ID);
        columns.Bound(m => m.Course);
        columns.Bound(m => m.City);
        columns.Bound(m => m.MyRegionName);
    })
    .Pageable()
    .Sortable()
    .Filterable()
    .Scrollable()
    .Groupable()    
    .DataSource(dataSource => dataSource
        .Ajax()
        .Read(read => read.Action("Index_Read", "Student"))
    )        
)

以下是可能导致Controller和View出现问题的点:

Here is the point that may cause the problem in the Controller and View:

City = m.City.Name, //I can get City name and show it in View.
MyRegionName = m.City.Region.Name //I can get region name and assign it to the  "MyRegionName" parameter in JSON. However in View I cannot get it using "MyRegionName" paremeter.

可能与Student实体中存在City参数有关.但是 City 实体中没有 MyRegionName 属性.

May it be related to that there is City parameter in the Student entity. But there is no MyRegionName property in the City entity.

推荐答案

在Index_Read"方法中，您正在创建IEnumerable of object"，即不是IEnumerable of Student"类型的学生.但鉴于您已将网格绑定到IEnumerable of Student".由于Student"类不包含MyRegionName"属性，这就是您遇到问题的原因.

In "Index_Read" method you are creating "IEnumerable of object" i.e. students which is not of "IEnumerable of Student" type. But in view you have binded your grid to "IEnumerable of Student". Since "Student" class doesn't contain "MyRegionName" property that's why you are facing issue.

试试这样的:

public ActionResult Index_Read([DataSourceRequest] DataSourceRequest request)
    {
        var dataContext = repository.Students;
        var students = dataContext.ToDataSourceResult(request, m => new StudentViewModel
        {
            ID = m.ID,
            Course = m.Course,
            CityName = m.City.Name, 
            RegionName = m.City.Region.Name 
        });           
        return Json(students, JsonRequestBehavior.AllowGet);
    }

public class StudentViewModel
{
    public int ID { get; set; }
    public string Course { get; set; }
    public string CityName { get; set; }
    public string RegionName { get; set; }
}

在视图中:

@model IEnumerable<StudentViewModel>

@(Html.Kendo().Grid<StudentViewModel>()
    .Name("Grid")
    .Columns(columns =>
    {
        columns.Bound(m => m.ID);
        columns.Bound(m => m.Course);
        columns.Bound(m => m.CityName);
        columns.Bound(m => m.RegionName);
    })
    .Pageable()
    .Sortable()
    .Filterable()
    .Scrollable()
    .Groupable()    
    .DataSource(dataSource => dataSource
        .Ajax()
        .Read(read => read.Action("Index_Read", "Student"))
    )        
)

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