在C＃中访问子类的属性

Question

I'm banging my head against a wall for what seems like a really simple thing, but there's clearly something small that I'm missing to get this to work.

I have the following code

public class PagedListArgs
{
     public class DataViewParts
     {
         private string _type;
         public string Type
         {
             get { return _type; }
             set { _type = value; }
         }

         private string _filter;
         public string Filter
         {
             get { return _filter; }
             set { _filter = value; }
         }  
     }
}

Later on I'm using these as follows:

PagedListArgs pagedListArgs = new PagedListArgs(...);
pagedListArgs.DataViewParts.Type = pagedListArgs.DataViewParts.Type.ToLower();

I'm getting the following exception

'DataViewParts': cannot reference a type through an expression; try 'PagedListArgs.DataViewParts' instead

What is it that I'm doing wrong?

EDIT

Okay, I did a poor job of explaining the issue I'm having, and that's on me. Basically the issue was that the constructor for DataViewParts was being fired every time you tried accessing it. Moving the constructor logic into PagedListArgs fixed the issue I was having.

Answer 1

DataViewParts is a class, not an instance of a DataViewParts, but you're trying to access it that way. Are you trying to do something like this?

public class PagedListArgs
{
     public PagedListArgs(){
         MyParts = new DataViewParts();
     }

     public DataViewParts MyParts { get; set; }

     public class DataViewParts
     {
         private string _type;
         public string Type
         {
             get { return _type; }
             set { _type = value; }
         }

         private string _filter;
         public string Filter
         {
             get { return _filter; }
             set { _filter = value; }
         }  
     }
}

Answer 2

You have only created the class for DataViewParts but no instance of it.

Either add an instance of your subclass to the main class or make the properties static. this way they can be accessed by the type name itself

For instance:

public class PagedListArgs
{
     public DataViewParts dataViewParts;

     public class DataViewParts
     {
         private string _type;
         public string Type
         {
             get { return _type; }
             set { _type = value; }
         }

         private string _filter;
         public string Filter
         {
             get { return _filter; }
             set { _filter = value; }
         }  
     }
}

Then you can access the instance by caliing

dataViewParts = new DataViewParty();
dataViewParts.DoStuff();

Answer 3

You should create an instance of nested class to get it's property.

public class PagedListArgs
{
     public DataViewParts viewParts;
     public class DataViewParts
     {
         private string _type;
         public string Type
         {
             get { return _type; }
             set { _type = value; }
         }

         private string _filter;
         public string Filter
         {
             get { return _filter; }
             set { _filter = value; }
         }  
     }
}

So the second part of code becomes

PagedListArgs pagedListArgs = new PagedListArgs(...);
pagedListArgs.DataViewParts.Type = pagedListArgs.viewParts.Type.ToLower();

Answer 4

When you create instance of PagedListArgs you do not create a instance of DataViewParts .

Do you mean, for example, setting a property in the constructor:

public class PagedListArgs
{
     public DataViewParts DataViewParts { get; set; }

     public PagedListArgs(){
         DataViewParts = new DataViewParts();
     }

     public class DataViewParts
     {
         private string _type;
         public string Type
         {
             get { return _type; }
             set { _type = value; }
         }

         private string _filter;
         public string Filter
         {
             get { return _filter; }
             set { _filter = value; }
         }  
     }
}