为了在实体框架中创建M-> M关系，你需要使用映射类，就像使用Config_OptionVal一样。现在重要的是，该映射类是关系任一侧的类通过的映射类，您不能忽略该关系中的该实体。因此：

  public   class  ConfigurationCollection 
 {
 public   int  ConfigurationCollectionID {获得跨度>;  set ; } 
 public   string  CollectionName { get 跨度>;  set ; } 
 public   int  LsystemID { get 跨度>;  set ; } 

 public   virtual  Lsystem Lsystem {获得跨度>;  set ; } 
 public   virtual  ICollection< Config_OptionVal> Config_OptionVals { get ;  set ; } 
} 
 public   class  OptionValue 
 {
 public   int  OptionValueID { get ;  set ; } 
 public   string  OptionVal { get 跨度>;  set ; } 
 public   int  OptionID { get 跨度>;  set ; } 

 public   virtual  ICollection< Config_OptionVal> Config_OptionVals { get ;  set ; } 
 public   virtual 选项选项{ get ;  set ; } 
} 
 public   class  Config_OptionVal 
 {
 public   int  Config_OptionValID { get ;  set ; } 
 public   int  OptionValueID { get 跨度>;  set ; } 
 public   int  ConfigurationCollectionID { get 跨度>;  set ; } 
 public   bool  OptionValChecked { get 跨度>;  set ; } 

 public   virtual  OptionValue OptionValue {获得跨度>;  set ; } 
 public   virtual  ConfigurationCollection ConfigurationCollection { get ;  set ; } 
} 

通过此关系访问使用Config_OptionVal，如下所示：

 myContext.Set< config_optionval>（）。其中​​（x = >  x.OptionValueID == IDofInterest）。 ToArray的（）; 

 myContext.Set< Config_OptionVal>（）。其中​​（x = >  x.ConfigurationCollectionID == IDofInterest）。ToArray（）; 

 ConfigurationCollectionObject.Config_OptionVal.Select（x = >  x.OptionValue）。ToArray（）; 

 OptionValueObject.Config_OptionVal.Select（x = >  x.ConfigurationCollection）。ToArray（）; 
< /   config_optionval  >  

因此，在您的控制器示例中，假设LSystem和ConfigurationCollection为1> 1：

  public  ActionResult Create（ int  LsystemID ）
 {
 var  model =  new  ConfigurationCollection 
 {
 LsystemID = LsystemID，
 Lsystem = db.Lsystem.FirstOrDefault（x = >  x.LsystemID == LsystemID），
 OptionValues = Lsystem！=  null  
？ Lsystem.ConfigurationCollection.Config_OptionVal.Select（x = >  x.OptionValues）。ToList（）
： new 列表< optionvalue>（）; 
}; 
 return 查看（模型）; 
} 
< /   optionvalue  >  

以及几个示例/教程：

MVC 5，实体框架6和多对多关系：一步一步查看模型方法 [ ^ ]



https://msdn.microsoft.com/en-us/library/dd742359.aspx [ ^ ]

I have 2 classes `ConfigurationCollection` and `OptionValues` which has a many to many relationship. I have tried solutions on the net to get it working. I tried adding another class to create two one to many relationship. But I am not understanding it the right way I suppose. And I also tried it without adding a third class.

Model classes

public class ConfigurationCollection
{
    public int ConfigurationCollectionID { get; set; }
    public string CollectionName { get; set; }
    public int LsystemID { get; set; }

    public virtual Lsystem Lsystem { get; set; }
    public virtual ICollection<OptionValue> OptionValues { get; set; }
}
public class OptionValue
{
    public int OptionValueID { get; set; }
    public string OptionVal { get; set; }
    public int OptionID { get; set; }

    public virtual ICollection<ConfigurationCollection> ConfigurationCollections { get; set; }
    public virtual Option Option { get; set; }
}
public class Config_OptionVal
{
    public int Config_OptionValID { get; set; }
    public int OptionValueID { get; set; }
    public int ConfigurationCollectionID { get; set; }
    public bool OptionValChecked { get; set; }

    public virtual OptionValue OptionValue { get; set; }
    public virtual ConfigurationCollection ConfigurationCollection { get; set; }
}

Controller

public ActionResult Create(int LsystemID)
{
    var model = new ConfigurationCollection
    {
      LsystemID = LsystemID,
      Lsystem = db.Lsystem.FirstOrDefault(x => x.LsystemID == LsystemID),
      OptionValues=new List<OptionValue>()
    };
    return View(model);
}

I am not sure what should be written in the Controller. I am able to populate the `OptionValues` in my View. I am just missing something that could save the data into the database.

In order to create a M->M relationship in entity Framework you'll need to use a mapping class, as you did with Config_OptionVal. Now it's important that that mapping class is the one that the classes on either side of the relationship operate through, you can't ignore that entity in the relationship. Therefore:

public class ConfigurationCollection
{
    public int ConfigurationCollectionID { get; set; }
    public string CollectionName { get; set; }
    public int LsystemID { get; set; }
 
    public virtual Lsystem Lsystem { get; set; }
    public virtual ICollection<Config_OptionVal> Config_OptionVals{ get; set; }
}
public class OptionValue
{
    public int OptionValueID { get; set; }
    public string OptionVal { get; set; }
    public int OptionID { get; set; }
 
    public virtual ICollection<Config_OptionVal> Config_OptionVals{ get; set; }
    public virtual Option Option { get; set; }
}
public class Config_OptionVal
{
    public int Config_OptionValID { get; set; }
    public int OptionValueID { get; set; }
    public int ConfigurationCollectionID { get; set; }
    public bool OptionValChecked { get; set; }
 
    public virtual OptionValue OptionValue { get; set; }
    public virtual ConfigurationCollection ConfigurationCollection { get; set; }
}

Access across this relationship uses Config_OptionVal, like this:

myContext.Set<config_optionval>().Where(x => x.OptionValueID == IDofInterest).ToArray();

myContext.Set<Config_OptionVal>().Where(x => x.ConfigurationCollectionID == IDofInterest).ToArray();

ConfigurationCollectionObject.Config_OptionVal.Select(x => x. OptionValue).ToArray();

OptionValueObject.Config_OptionVal.Select(x => x.ConfigurationCollection).ToArray();
</config_optionval>

So in your controller example, assuming LSystem and ConfigurationCollection are 1->1:

public ActionResult Create(int LsystemID)
{
    var model = new ConfigurationCollection
    {
      LsystemID = LsystemID,
      Lsystem = db.Lsystem.FirstOrDefault(x => x.LsystemID == LsystemID),
      OptionValues= Lsystem != null 
          ? Lsystem.ConfigurationCollection.Config_OptionVal.Select(x => x.OptionValues).ToList() 
          : new List<optionvalue>();
    };
    return View(model);
}
</optionvalue>

And a couple of examples/tutorials:
MVC 5, Entity Framework 6 and Many to Many Relationship : a step by step View Model approach[^]

https://msdn.microsoft.com/en-us/library/dd742359.aspx[^]