Today, while working on an application for ClickOnce deployment, I faced a small issue, which took almost a half an hour. My task was to associate a default icon to my Application. Thus, in order to do this, I went to my project properties and simply set the icon, as shown below:

publish

As you can see in the screenshot, shown above, it is showing an error icon which states: 'Icon file is not set to be published with the Application or is not a part of the required download group'.

Now, I built my Application and landended up with the error message, shown below, which is more clear:

error

After hitting my head for many minutes, I thought, let's check out what is this 'download group'.

On surfing the net, I got the clue that download group is nothing but a collection of files, which are going to be a part of our publishing activity.

Thus, I quickly opened Application files dialog, using Project properties >> Publish. The Application files dialog looks like:

dialog

I noticed that my icon file is not listed above. Thus, I got an idea on what went wrong :)

I immediately changed "to build action" to 'Content' and forced it to 'Copy Always'. Guess what?
My error has gone :)

After fixing this issue, I realized, that it was very silly. As it wasted many minutes, I thought to add it to my repository, so that it can be useful for all others, who got stuck like me :(

Happy troubleshooting !!!