C＃背颜色变化

Question

I just started studying C# in university and I have a problem with something. I need to make the back color change when I click one button with if-statement. My code is this:

BackColor = Color.Red;
if ( BackColor == Color.Red)
{
    BackColor = Color.Blue;
}
if (BackColor == Color.Blue)
{
    BackColor = Color.Green;
}

The problem is the back color changes to green instantly.. what should I do to make it change in the three colors? Sorry if the question is dumb.

Answer 1

You need to understand the if condition s. The first if evaluates to true because you just assigned Color.Red to BackColor then the second if is also true because you just assigned Color.Blue to it.

Also if you initialize BackColor with Color.Red the first will be always true so it will be Blue this way. I guess you want to do this:

 if (BackColor == Color.Green) 
 {
     BackColor = Color.Red;
 }
 else if (BackColor == Color.Red)
 {
     BackColor = Color.Blue;
 }
 else if (BackColor == Color.Blue)
 {
     BackColor = Color.Green;
 }

I would suggest you to read more about if conditions . Also, like Rotem suggested, please check about switch too.

Answer 2

Applies only if the use of "if" is not mandatory:

class xyz{
    private Color[] myColors = new Color[]{ Color.Red, Color.Blue, Color.Green }
    private int colorIndex = 0;

    // BackColor also declared somewhere here ...

    private void clickHandler( object sender, EventArgs e )
    {
         colorIndex = (++colorIndex)%myColors.length; 
         // ++ColorIndex is short for colorIndex = colorIndex + 1
         // % - "Remainder" => when colorIndex is 3 then 3 % 3 ( Remainder of 3 / 3 ) = 0
         // So this will increment on each click and "reset to 0" on 3, so you stay in bounds.
         BackColor = myColors[ colorIndex ];
    }
}

Answer 3

Put this in the constructor

BackColor = Color.Green;

And but this inside the onclick method

if (BackColor == Color.Green) 
{
    BackColor = Color.Red; 
} 
else if (BackColor == Color.Red)
{
    BackColor = Color.Blue;
} 
else if (BackColor == Color.Blue)
{ 
    BackColor = Color.Green; 
}

That should work for you