Question

How would I check if certain fields are incomplete?

I want it so that whenever somebody clicks my button called “ADD?” that a messagebox will appear if required fields have not been properly filled out.

Answer 1

In your event handler for the “Add” button, just check to see if the “field” has been filled in, and if not, don’t continue:

void buttonAdd_Click(object sender, EventArgs e)
{
    if (string.IsNullOrWhiteSpace(textBoxField.Text))
    {
         // Show message?
         MessageBox.Show(....);

         return; // Don't process
    }

    // Field has a value, do your thing here...

}