How can I draw a line in my form from another class?

Question

I have 3 classes in my program:

• Arrow (it contains the logic for drawing arrow, and all required information about it, like: starting point, ending point, etc.)

• Form1 (that contains the drawing area(basically panel), where this arrow will be located in the future)

• UserControl, is located in Form1 (I did Form1.Controls.Add(UserControl)). It has a Form1 as a parent. In this UserControl, I have a button, when I click it, an arrow should be drawn on the Form1's drawing area.

  And I'm so confused with the logic that this program should have. I tried to create Arrow class object in the UserControl.Button_Click(), and call all the Arrow's methods from there, but I can't access to Form1's controls. I also thought maybe I can create object of Arrow in the Form1. So I tried to subscribe event UserControl.Button_Click() with some Form1's delegate, but I don't know how to do it. In this case, does delegate and the method that this delegate have as a reference should be Static?

So this is how my code looks like. (I little bit simplified and shortened my classes) Arrow:

public class Arrow
{
    public Point PointBeginning { get => pointBeginning; set => pointBeginning = value; }
    public Point PointEnding { get => pointEnding; set => pointEnding = value; }
    public int ArrowClickCounter { get => arrowClickCounter; set => arrowClickCounter = value; }

    public void Draw(object sender, MouseEventArgs e)
    {
        //code for drawing
    }
}

Form1:

public class Form1
{
    public delegate void DrawArrowDelegate(object sender, MouseEventArgs e);
    DrawArrowDelegate drawArrowDelegate = DrawArrow;
    /* .. */

    private void DrawArrow(object sender, MouseEventArgs e)
    {
        Arrow arrow = new Arrow();
        arrow.PointBegining = //some point
        arrow.PointEnding = //some another point
        arrow.Draw(sender, e);
    }
}

UserControl:

public class UserControl
{
    /*...*/
    
    private void button_MouseClick(object sender, MouseEventArgs e)
    {
        //And here i somehow want to call delegate. But don't know how :(
    }
}

Sorry for such confused code :(

Can you please recommend me something?

Answer 1

1. Your Arrow class could potentially have a DrawMethod which takes a control
2. Your UserControl, should publish events
3. You form should listen to the UserControl Events
4. Your form should override OnPaint to draw the method on demand

Answer 2

Arrow class:

    public class Arrow
    {
        public Point PointBeginning { get; set; }
        public Point PointEnding { get; set; }
        public int ArrowClickCounter { get; set; }

        public void Draw()
        {
            //code for drawing
        }
    }

UserControl.cs:

    public delegate void CreateArrowEventArgs(Arrow arrow);
    public event CreateArrowEventArgs OnCreateArrow; 
    private void button1_Click(object sender, EventArgs e)
    {
        if(this.OnCreateArrow!=null)
        {
            // Create Arrow object which you will have access to in your Form
            Arrow arrowToDraw = new Arrow();

            // Fire The Event
            this.OnCreateArrow.Invoke(arrowToDraw);
        }
    }

Form codebehind :

    private void Form1_Load(object sender, EventArgs e)
    {
        // Create User Control
        var UserCtrl = new UserControl1();

        // Register Event
        UserCtrl.OnCreateArrow += UserCtrl_OnCreateArrow;

        //Add Control to Form
        this.Controls.Add(UserCtrl);
    }

    // You get the Arrow object for use here
    private void UserCtrl_OnCreateArrow(Arrow arrow)
    {
        arrow.Draw();
    }

Answer 3

It sounds like you're having trouble accessing Form1's Controls, so try this:

Form1 f1 = new Form1();

foreach(Button b in f1.Controls)
{
  //Your code..
}

There's also:

this.Controls

And, with calling the events of another control,

button1_Click(sender, e);

As for adding an event to the click of, say, a button,

button1.Click += button1_Click;

Those should work to access the controls.

I can provide more information if needed :)