title: Index Attribute resolving issue in Microsoft.EntityFrameworkCore
body: <p>I have got .Net Standart 2.0 dll to keep separated entities of MS SQL Server.</p>
  <p>The <code>Index Attribute</code> cannot be resolving.</p>
  <p><strong>I've did search and experimented with adding some namespaces of Entity Framework but nothing works even by <a href="https://docs.microsoft.com/en-US/ef/core/modeling/indexes?tabs=data-annotations" rel="nofollow noreferrer">MSDN</a>.</strong></p>
  <p>Please, help. Thank you!</p>
  <p><a href="https://i.stack.imgur.com/hYzxe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hYzxe.png" alt="enter image description here" /></a></p>
  <p><a href="https://i.stack.imgur.com/85aNg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/85aNg.png" alt="enter image description here" /></a></p>