[2010] What is wrong with the code?

[senthilkumartd]

Hi, Here I gave the code. My aim : I am trying to make the frmView to generic for populating from Manager Class List.

namespace WindowsFormsApplication1
{
    public abstract class AbsLookUpView 
    {
        public abstract string LookupName{get;}
    }
}


--------------------------------------------------------------------------

namespace WindowsFormsApplication1
{
    public abstract class AbsManager<T> where T:AbsLookUpView
    {
      public abstract List<T> LoadAll();

    }
}

==========================================================

public partial class Department: AbsLookUpView
    {
        public override string LookupName
        {
            get
            {
                return "Department";
            }
        }
    }

==========================================================


namespace WindowsFormsApplication1
{
    public class DeptManager : AbsManager<Department>
    {
        private DataClasses1DataContext dc = new DataClasses1DataContext();


        public override List<Department> LoadAll()
        {
            return dc.Departments.ToList<Department>();
        }
    }
}


==========================================================

namespace WindowsFormsApplication1
{
    public partial class frmView : Form
    {
        public AbsManager<AbsLookUpView> ManagerCls;


        public void BindGrid()
        {
            this.lkpDataGridView.DataSource = ManagerCls.LoadAll();
        }

    }
}

==========================================================

namespace WindowsFormsApplication1
{
    public partial class frmTest : frmView
    {
        public frmTest()
        {
            InitializeComponent();
        }



        private void frmTest_Load(object sender, EventArgs e)
        {

            AbsManager<AbsLookUpView> dmb ;

            DeptManager dm = new DeptManager();
            dmb = dm; [Error in this line is given below]
            this.ManagerCls = dmb;
            this.BindGrid();
            
            Form5 f = new Form5(this);
            this.ChildForm = f;

        }
    }
}

==========================================================
Error: Cannot implicitly convert type 'WindowsFormsApplication1.DeptManager' to 'WindowsFormsApplication1.AbsManager<WindowsFormsApplication1.AbsLookUpView>' E:\test\WindowsFormsApplication1\WindowsFormsApplication1\frmTest.cs


here, DeptManager is inherited from AbsManager<WindowsFormsApplication1.AbsLookUpView>. Then why it throws error. Pls explain.

What is wrong with the above code. Why is this error is occuring? Pls explain experts.

[techgnome]

"DeptManager is inherited from AbsManager<WindowsFormsApplication1.AbsLookUpView>"
It is?
You have: public class DeptManager : AbsManager<Department>
If it inherited from AbsLookUpView wouldn't it look like this:
public class DeptManager : AbsManager<AbsLookUpView>

Or did I miss something?


-tg

Edit - never mind... I did miss something... ok... back to square 1.

[jmcilhinney]

The fact that String inherits Object does not mean that List<String> inherits List<Object>. Likewise, the fact that Department inherits AbsLookUpView does not mean that AbsManager<Department> inherits AbsManager<AbsLookUpView>. Your DeptManager class inherits AbsManager<Department> so it can be cast as type AbsManager<Department>. It doesn't inherit AbsManager<AbsLookUpView> so it can't be cast as that type.

[senthilkumartd]

Then, how can we change this code to achieve the aim. Any suggestion to achieve this

[jmcilhinney]

Then, how can we change this code to achieve the aim. Any suggestion to achieve this

You have to change your aim.