title: Regular expression to match alphabetic string and require at least one uppercase and one lowercase (vb.net)
body: <p>I am trying to write a regular expression string match in vb.net. The condition that I am trying to implement is that the string should contain only alphabets and must contain atleast one letter of both lower and upper case. i.e AAA-fail, aaa-fail, aAaA-pass.</p>
  
  <p>The regular expression that I have come up with is <code>^(([a-z]+[A-Z]+)+|([A-Z]+[a-z]+)+)$</code></p>
  
  <p>Can someone suggest some better/simpler regular expression for the same?</p>