Question

I have a small program that contains one button called button1and one panel called panel1which has a color green. So far the program allows you to drag button1 around the form. I am trying to expand this program so when button1 is dropped on panel the panel will change color to red.

The form:

The code so far:

System.Drawing.Point OldPosition; 

public Form1()
{
    InitializeComponent();
}

private void button1_MouseDown(object sender, MouseEventArgs e)
{
    //Only prepare if the button click down is the left button  
    if (e.Button == MouseButtons.Left)
    {
        //Store the current mouse location  
        OldPosition = e.Location;
        //Change the mouse cursor if you want  
        button1.Cursor = Cursors.Hand;
    }  
}

private void button1_MouseMove(object sender, MouseEventArgs e)
{
    //Only move if the left button still down  
    if (e.Button == MouseButtons.Left)
    {
        button1.Location = new Point(button1.Location.X + (e.X - OldPosition.X), button1.Location.Y + (e.Y - OldPosition.Y));
    } 
}

private void Form1_Load(object sender, EventArgs e)
{
    panel1.BackColor = Color.Green;        
}

private void panel1_MouseEnter(object sender, EventArgs e)
{
    if (button1.Location == panel1.Location)
        panel1.BackColor = Color.Red; //im not sure how to do this part
}

Answer 1

Try the code below:

private void button1_MouseMove(object sender, MouseEventArgs e)
{
    //Only move if the left button still down  
    if (e.Button == MouseButtons.Left)
    {
        button1.Location = new Point(button1.Location.X + (e.X - OldPosition.X), button1.Location.Y + (e.Y - OldPosition.Y));

        //CHECK IF NEW LOCATION IS WITHIN PANEL BOUNDS
        if (panel1.Bounds.Contains(button1.Location))
           panel1.BackColor = Color.Red;
        else
           panel1.BackColor = Color.Green;
    }
}

Also in the designer you may need to “SEND TO BACK” the panel1 control otherwise the button will not be visible if it goes over the panel.