title: Simplest way to perform data validation for fields on Windows Forms
body: <p>I have a windows form project in which I want to force the user to enter values in certain fields before he presses the calculate button at the bottom. The fields include  three pairs of <strong>radio buttons</strong>, five <strong>text boxes</strong> and one <strong>combo box</strong>. So basically all these fields need to contain a value in order to perform the calculations. Additionally, the <strong>text boxes</strong> should contain <strong>numbers</strong> - any double values. Moreover, I want to set a <strong>maximum</strong> value set for most of these <strong>text boxes</strong> which the user cannot exceed. Please let me know what is the simplest way to achieve this. I don't see field validating controls for winform projects like those available in ASP.Net. Please note, I am working on .net 3.5. Currently, I am using the message boxes to communicate this to the user i.e. whenever the user does press calculate I display message boxes mentioning the name of the required fields which are presently empty.</p>