title: Check a string to see if all characters are hexadecimal values
body: <p>What is the most efficient way in C# 2.0 to check each character in a string and return true if they are all valid hexadecimal characters and false otherwise?</p>
  <h3>Example</h3>
  <pre><code>void Test()
  {
      OnlyHexInString(&quot;123ABC&quot;); // Returns true
      OnlyHexInString(&quot;123def&quot;); // Returns true
      OnlyHexInString(&quot;123g&quot;); // Returns false
  }
  
  bool OnlyHexInString(string text)
  {
      // Most efficient algorithm to check each digit in C# 2.0 goes here
  }
  </code></pre>