title: How to convert string to custom object with Convert
body: <p>I found following statement in <code>Programming in C#</code> book:</p>
  
  <blockquote>
    <p>IFormattable provides the functionality to format the value of an object 
        into a string representation. It is also used by the Convert class to do the opposite.</p>
  </blockquote>
  
  <p>I have class:</p>
  
  <pre><code>class a : IFormattable
  {
      private string aa = "123";
      private int bb = 5;
  
      public string ToString(string format, IFormatProvider formatProvider)
      {
          return $"aa={aa} bb={bb}" ;
      }
  }
  </code></pre>
  
  <p>But how to convert string by using Convert into object of <code>a</code>?</p>
  
  <p>UPD:
  I know idea of parsing. But my question is how to use Convert class to create new object from string.</p>