Re: Question For List Generics - C# Discussion Boards

0x3c013-Jun-09 23:22

13-Jun-09 23:22

You're trying to cast the objects inside the List, but you're actually casting the List itself. If you're using version 3.5 of the .Net Framework, then you can simply use return LoadChild(ID).Cast<City>();

Between the idea
And the reality
Between the motion
And the act
Falls the Shadow

Re: Question For List Generics

Sider8913-Jun-09 23:36

Sider89

13-Jun-09 23:36

WELL i have done LoadChild(ID).Cast< City >();

but Error occurs aggain: Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<g1_onlinestoreobjects.city>' to 'System.Collections.Generic.List< G1_OnlineStoreObjects.City >'. An explicit conversion exists (are you missing a cast?)

C# Developer

Re: Question For List Generics

0x3c014-Jun-09 0:57

0x3c0

14-Jun-09 0:57

This is because the extension method Cast() returns an IEnumerable<t>. Just cast it to the property's type and you're done

Between the idea
And the reality
Between the motion
And the act
Falls the Shadow

Re: Question For List Generics

Sider8914-Jun-09 1:04

Sider89

14-Jun-09 1:04

I did not understand

right that: (City)LoadChild(ID).Cast< City >();

but occuers Error again

C# Developer

Re: Question For List Generics

0x3c014-Jun-09 1:36

0x3c0

14-Jun-09 1:36

LoadChild(ID).Cast<City>() as List<City>;
Besides that, you seem to have a small amount of confusion with List casting. When you cast a List to a City, you do not cast the elements in the List, only the List itself. In order to cast the elements inside the List, you need to use the Cast() method. This method returns an IEnumerable; because List implements IEnumerable, you can cast the List. This does not cast the elements, just the containing class

Between the idea
And the reality
Between the motion
And the act
Falls the Shadow

Re: Question For List Generics

Sider8914-Jun-09 5:30

Sider89

14-Jun-09 5:30

well it's works but there is some another problem like this:
Here is class where I invoked function into delegate

public class CountryDAO : BaseDAO< Country >
{

public override Country Load(int id) //I try to do lazyloading
{
Country country = base.Load(id); //just loads from database to Country class objects
if (country != null)
{
country.LoadChild = LoadCity;// here I invoked it and here occurs error
}
return country;
}

private List< City > LoadCity(int parentId)
{
CityDAO cDao = new CityDAO();
return cDao.LoadList("CountryID=" + parentId.ToString());
}

}

Error: 'System.Collections.Generic.List< G1_OnlineStoreObjects.City > G1_OnlineStoreDAO.CountryDAO.LoadCity(int)' has the wrong return type

what's the matter, why cann't compile it?
I repeat it what you said me to cast bu it is not works again Frown | :(

C# Developer

Re: Question For List Generics

0x3c014-Jun-09 5:47

0x3c0

14-Jun-09 5:47

This is because you have the wrong return type. The delegate is of type List<Country> LoadChild(int id), but the delegate you try to convert it to is of type List<City> LoadChild(int id). That's the main problem, but it seems more architectural than syntactic. Either your delegate type is wrong, City does not inherit from Country, or City and Country don't implement a common interface. Personally, I wouldn't use a generic delegate at all; I'd go for something like this:

public delegate List<City> LoadCitiesDelegate(int countryId);

public class CountryDAO : BaseDAO<Country>
{
    public override Country Load(int id)
    {
        Country country = base.Load(id);

        if(country != null)
            country.LoadChild = loadCity;
        return country;
    }

    private List<City> LoadCities(int countryId)
    {
        CityDAO cDao = new CityDAO();

        return cDao.LoadList("CountryID=" + countryId.ToString());
    }
}

This probably wouldn't compile, but it's a general idea of the way I would personally do it

Between the idea
And the reality
Between the motion
And the act
Falls the Shadow

Re: Question For List Generics

Sider8914-Jun-09 19:39

Sider89

14-Jun-09 19:39

Maybe it'll work, but in my project I have many classes and Functions with generics and it's almost impossible to change all Big Grin | :-D

I think I solve this like this, I write it:

public delegate List< T > LoadChildHandler< T >(int parentId);

public class ObjectBase< T >
{
public int ID { get; set; }
}

public class Country : ObjectBase< Country >
{

public LoadChildHandler< City > LoadChild; // I just declare delegate in child class and there are not resist between City and Country, well works fine

public string CountryName { get; set; }

public List< City > Cities
{
get
{
return LoadChild(ID);
}
}
}

and so all I want it to do in a different way...
Now I must dclare this delegate in other classes too, it would be fine to do solve this problem, without declaring in other classes and not such torture Smile | :)

C# Developer

Closing and recreating a form

SimpleData13-Jun-09 22:43

SimpleData

13-Jun-09 22:43

Hi I have a Windows form called mainwindow in my project. After it completes what it does, it closes and then recreates itself. But as I have noticed lately it recreates but doesnt't close itself.

Here is my code:

private void RestartAll()
{
   // These are not that important, only to transfer the same properties of the form to the new form.
   depo.multipleformlocation=this.Location;
   depo.multipleform = true;
   depo.ekrangoruntusuadedi = 0;

   this.Hide();

   mainwindow _mainwindow = new mainwindow();
   _mainwindow.ShowDialog();

   this.Close();

   // Here is my temporary solution (putting old form's thread to sleep infinitely because it shouldn't keep doing what it does)
   Thread.Sleep(Timeout.Infinite);
}

How can I close(destroy) the old form completely and recreate that form? When I don't completely close that old form, because I do this closing and recreating process more than once my App's memory usage gets much higher.

Thanks in advance.