title: How do you set a value in a ConcurrentDictionary regardless of whether it contains the Key
body: <p>First of all, is it safe to simply add an item to a concurrent dictionary using the indexed assignment (e.g. <code>myConcurrentDictionary[someKey] = someValue;</code>)?</p>
  
  <p>I'm just confused because it hides the IDictionary methods (e.g. <code>Add</code>).</p>
  
  <p>Why does AddOrUpdate() require a func to update the value? Is there a method to set the value for a key regardless of whether the key already exists?</p>
  
  <p>I couldn't really gather this from the MSDN page.</p>