How to load a class which extended from a form and interface?

Question

I have few forms class which extended based Form and my custom interface.

Interface InterfaceForms{
      void InterfaceFunc1();
}



public partial class child1 : Form, InterfaceForms
    {
      public child1(){}
      public InterfaceFunc1(){}
    }

public partial class child2 : Form, InterfaceForms
    {
      public child2(){}
      public InterfaceFunc1(){}
    }

I added all the form classes object to a list as below:

 List<Form> lsf = new List<Form>();

then I tried to load the my form classes as below:

 var fr = from Form item in lsf
                         where item.Name == "child1"
                         select item;
Form frm = (Form)fr;

Now, my problem is I cannot access to InterfaceFunc1().

Would you mind advising me how I can implement this? Please take note that frm type might be diffrent each time (child1, child2 & etc) but all of them are extended from Form and InterfaceForm.

Answer 1

You need to cast it as InterfaceForms:

var fr = from Form item in lsf
                         where item.Name == "child1"
                         select item;
Form frm = (Form)fr;
var iFaceFrm = frm as InterfaceForms;

if (iFaceFrm != null)
{
    //use the iFaceFrm or frm here
}

Edit

The issue with your LINQ statement is declaring the type, the type of a LINQ statement is inferred, so you don't put it in the select:

var fr = from item in lsf
         where item.Name == "child1"
         select item;

Or, if you want to do it proceduraly:

var fr = lsf.Where(f => f.Name == "child1").FirstOrDefault();