Question

I have 2 forms and I want to call a function of Form1 defined in an interface from Form2. I tried using delegates and events. Is there a better way of doing this?

Form1

namespace atszodidb
{
    public partial  class Form1 : Form
    {

    }
}

interface db
{
    void func(string param);
}

class db_veiksmai : db // veiksmai = actions
{

    public db_veiksmai()
    {

    }

    public  void func(string param)
    {
        MessageBox.Show(param);
    }
}

Form2

namespace atszodidb
{
    public partial class Form2 : Form
    {
        void function()
        {

        }
    {
}

How to call void func(string param) from function void function()? I tried to do this with a delegate:

Program.cs

public static class Data
{
    public delegate void MyEvent(string data);
    public static MyEvent EventHandler;
}

and in Form2

Data.EventHandler("lalalal");

However, I don’t know where to write Data.EventHandler = new Data.MyEvent(func);. I tried in the constructor of class db_veiksmai, but it’s a bad solution.

Answer 1

You need an instance of a class in order to call an instance method. So:

public partial class Form2 : Form
{
    void function()
    {
        db_veiksmai mydb = new db_veiksmai();
        mydb.func("some parameter");
    }
}

Or have your Form2 take the interface as a constructor dependency:

public partial class Form2 : Form
{
    private readonly db _mydb;
    public Form2(db mydb)
    {
        _mydb = mydb;
    }

    void function()
    {
        _mydb.func("some parameter");
    }
}

and now it will be the responsibility of the consumer of Form2 to pass a specific implementation of db when constructing Form2.

Remark: in .NET as a convention interface names start with I, and db is a very poor name for an interface.