System.InvalidCastException C#

Question

I designed a Form that has Panels and Labels. I made the cursor property of the panels by hand. But when I click on the panel I get this Exception :

Unable to cast object of type 'System.Windows.Forms.Panel' to type 'System.Windows.Forms.Label'

This is my code:

using System;
using System.Drawing;
using System.Windows.Forms;

namespace Mancula
{

    public partial class Form2 : Form
    {  
        private System.Windows.Forms.Panel[] pan;
        private System.Windows.Forms.Label[] lab;
        Graphics g;
        Pen pen = new Pen(Color.Red);
        SolidBrush br = new SolidBrush(Color.Red);
        Rectangle rec = new Rectangle(10, 10, 30, 30);

        int player1 = 49;
        int player2 = 49;
        int playerturn = 0;

        public Form2()
        {
            InitializeComponent();

            label1.Text = "0";
            label2.Text = "0";

        }

        public void startgame()
        {
            if (radioButton1.Checked == true)
            {
                playerturn = 1;
            }
            else
            {
                playerturn = 2;
            }

        }

        private void button15_Click(object sender, EventArgs e)
        {
            button1.Enabled = button2.Enabled = true;
            button3.Enabled = button4.Enabled = true;
            button5.Enabled = button6.Enabled = true;
            button7.Enabled = button8.Enabled = true;
            button9.Enabled = button10.Enabled = true;
            button11.Enabled = button12.Enabled = true;
            button13.Enabled = button14.Enabled = true;

            panel1.Enabled = panel2.Enabled = true;
            panel3.Enabled = panel4.Enabled = true;
            panel5.Enabled = panel6.Enabled = true;
            panel7.Enabled = panel8.Enabled = true;
            panel9.Enabled = panel10.Enabled = true;
            panel11.Enabled = panel12.Enabled = true;
            panel13.Enabled = panel14.Enabled = true;

            label1.Text = player1.ToString();
            label2.Text = player2.ToString();
            startgame();
            panel15.Enabled = false;

            for (int i = 0; i < 14; i++)
            {
                 pan [i].Click += new System.EventHandler(this.ClickHandler);
            }

        }

        private void ClickHandler(object sender, EventArgs e)
        {
            Panel temppanel = (Panel)sender;             
            Label templab = (Label)sender;

            if (playerturn == 1)
            {
                if (player1 == 0)
                {
                    playerturn = 2;
                }
                else
                {
                    player1 = player1 - 1;
                    if (templab.Text != "7")
                    {
                        g = temppanel.CreateGraphics();
                        g.DrawRectangle(pen, rec);
                        label1.Text = player1.ToString();
                    }
                }
            }
            else
            {
                if (player2 == 0)
                {
                    playerturn = 1;
                }
                else
                {
                    player2 = player2 - 1;
                    if (templab.Text != "7")
                    {
                        g = temppanel.CreateGraphics();
                        g.DrawRectangle(pen, rec);
                        label2.Text = player2.ToString();
                    }
                }
            }
        }
        private void Form2_Load(object sender, EventArgs e)
        {
            pan = new Panel[14] { panel1, panel2, panel3, panel4, panel5, panel6,panel7,
                                  panel8,panel9,panel10,panel11,panel12,panel13,panel14
                                };
            lab = new Label[14] { lab1,lab2,lab3,lab4,lab5,lab6,lab7,lab8,lab9,lab10,lab11,lab12,lab13,lab14};

        }
    }
}

NicoRiff · Accepted Answer · 2016-12-27 19:32:33Z

3

I think your mistake is this line:

    Panel temppanel = (Panel)sender;             
    Label templab = (Label)sender;

You should check the type before doing the cast.

You can do this:

if(sender.GetType() == typeof(Panel))
{
     Panel temppanel = (Panel)sender; 
}
else
{
     Label templab = (Label)sender;
}

Anyway, it doesn´t seem a good idea to assign the same handler to different types of objects. My recommendation would be to make a handler for each type of control.

edited Dec 27, 2016 at 19:32

answered Dec 27, 2016 at 19:05

NicoRiff

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4 Comments

Emad Over a year ago

Thanks. Can I use both (Panel) and (Label) ?

NicoRiff Over a year ago

given the code above you can do that. You can also use an IF... ELSE IF condition to make sure it only would be casting for Labels and Panels.

Emad Over a year ago

Thank you so much.

Emad Over a year ago

You Got it . Thank you :) .

Alex Sikilinda · Accepted Answer · 2016-12-27 19:04:56Z

1

In your event handler you have:

Panel temppanel = (Panel)sender;             
Label templab = (Label)sender;

But sender can be either Panel or Label, that why one of this cast will fail anyway.

answered Dec 27, 2016 at 19:04

Alex Sikilinda

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1 Comment

Emad Over a year ago

Thanks. How can I use both (Panel) and (Label) ?

rory.ap · Accepted Answer · 2016-12-27 19:05:14Z

0

Your problem is on this line:

Label templab = (Label)sender;

When you click on the panel, the sender is a Panel, not a Label, so you can't cast it as such.

answered Dec 27, 2016 at 19:05

rory.ap

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