Are controls empty?

I need to check 4 controls (2 combo boxes and 2 text boxes) and make sure they are not empty. I am unsure of how to do this in c#. I need something like...

re: Are controls empty?

The correct syntax to check for an empty string is:

For a combo box:

The MSDN is a great resource for help on syntax and the .NET framework, it should help you alot in your future study of C#.

re: Are controls empty?

I think a combo box can have items but still have a null selected item, can't it?

I'd say it would be safer to check if the list of combo box items is empty... but I guess it depends on the settings of the combo box and your definition of empty :D

re: Are controls empty?

for your "and" use &&

re: Are controls empty?

You really might want to look at the ErrorProvider class.
For just a little more work it's nice to have Error Alerts pop up next to the controls that have problems.

Basically you create a small method for validation, for each control. If the data fails validation an alert (exclamation in a red circle) appears next to the control. This can run when leaving a control for example.

Then you make a method that runs all of your other qualification methods, when you want to validate the entire form, like for an [Apply] button.