title: C# arrays with unknown size
body: <p>I need class with array inside:</p>
  
  <pre><code>class FirstClass
  {
       int x = 0;
       int y = 0;
  }
  
  class SecondClass
  {
      FirstClass[] firstclass = ???????? // size of array is unknown
      OtherClass[][] otherclass = ???????? // i need also multidimensional array or array of arrays
  }
  </code></pre>
  
  <p>Normally im using <code>List&lt;&gt;</code> for purposes like this, but today i need fastest possible solution (a lot of data to process), and i think Array should be faster than List (I've read somewhere that List is a lot slower than Array).</p>
  
  <p>Question is - what to put into "????????" in my code?</p>
  
  <p>Edit:</p>
  
  <p>My class is a neural network object. Biggest array will contain learning data (100000+ data rows with 50+ fields, float or double datatype). </p>
  
  <p>If Array is 1% faster than List - i need Array.</p>