[RESOLVED] ListBoxItem colour and percentages

[sciguyryan]

Hi guys!

I've got a list box full of items that have percentage values. What I need to do is colour code the background of the listbox items depending on the value of the percentage smoothly from green (being 100%) to red (0%).

I can't seem to think how to do this, so advice or an existing piece of code would be a great help.

Thanks!

[jmcilhinney]

You use the term "ListBoxItem" in the thread title. Does that mean that this is an ASP.NET application, because that's the only place you would find a ListBoxItem object, other than an upgraded VB6 app. If this is a web app then you should tell us or, better yet, post in the ASP.NET forum, which is designed for ASP.NET questions. If it's not a web app then you must not be using ListBoxItem objects, so you're thread title is misleading. It's very important to be clear so that we don't waste our time and yours with irrelevant answers.

[sciguyryan]

it's actually WPF. But since the code is not about WPF but about generating a background colour using C# code I didn't think it would matter.

However if anyone feels differently feel free to move the thread elsewhere.

To be clear I was thinking of something along the lines of:

100% = completely green
0% = completely red

And between the the two the colour is faded from one to the other depending on the percentage.

[jmcilhinney]

It's simple mathematics. A Color is created from red, blue and green components in the value 0 to 255. Use 0 for the blue, a percentage of 255 for the green and 100 less that percentage of 255 for the red.

[sciguyryan]

I know that part. I just can't seem to get the correct formula to face from 100% green too 100% red depending on the percentage.

I don't suppose you know how?

[jmcilhinney]

You don't know how to calculate a percentage of 255?

double percentage; // e.g. 78.2
double green = 255.0 * percentage / 100.0;
double red = 255.0 * (100.0 - percentage) / 100.0;

You round and convert to bytes and pass the results to Color.FromRgb.

[sciguyryan]

I do. Just I've never used them like that before. I think I had a case of over complication since I was ending up using something that was 3 lines long... D'oh. Thanks