I am validating input on a form and attempting to prompt the user of improper input(s) based on the combination of controls used.

For example, I have 2 combo boxes and 3 text boxes. The 2 combo boxes must always have a value other than the first (default) value, but one of three, or two of three, or all text boxes can be filled to make the form valid.

In one such scenario I have a 6 line if statement to try to make the test easily readable:

if ((!String.Equals(ComboBoxA.SelectedValue.ToString(), DEFAULT_COMBO_A_CHOICE.ToString())
    && !String.IsNullOrEmpty(TextBoxA.Text)
    && !String.Equals(ComboBoxB.SelectedValue.ToString(), DEFAULT_COMBO_B_CHOICE.ToString()))        
    ||
    (!String.IsNullOrEmpty(TextBoxB.Text)
    || !String.IsNullOrEmpty(TextBoxC.Text)))
{
    //Do Some Validation
}

I have 2 questions:

1. Should this type of if statement be avoided at all cost?

2. Would it be better to enclose this test in another method? (This would be a good choice as this validation will happen in more than one scenario)

Thanks for your input(s)!