title: What is ImmutableArray in c#
body: <p>I see <a href="https://nuget.org/packages/Microsoft.Bcl.Immutable/" rel="noreferrer">this</a>:</p>
  
  <blockquote>
    <p>This packages provides collections that are thread safe and guaranteed
    to never change their contents, also known as immutable collections.</p>
  </blockquote>
  
  <p>But i dont understand what is exactly and when we should use ImmutableArray?</p>
  
  <p>Edit: nowadays, Microsoft's github package has become part of the .NET ecosystem. <a href="https://docs.microsoft.com/en-us/dotnet/api/system.collections.immutable.immutablearray?view=netcore-3.1" rel="noreferrer">Reference is now here</a>. </p>