title: How can I migrate from ASP.NET Core 2.1 to 2.2 easily?
body: <p>I have a project which made by asp.net core 2.1, and now I wanna to migrate to the 2.2 version.</p>
  
  <p>I installed the SDK of 2.2 and changed the target framework to 2.2 in properties of the project.</p>
  
  <p>After I clean&amp;rebuild the solution, there are some warnings here I can not clean it:<br/>
  1.
  <a href="https://i.stack.imgur.com/lwVke.png" rel="noreferrer"><img src="https://i.stack.imgur.com/lwVke.png" alt="enter image description here"></a></p>
  
  <p>2.
  <a href="https://i.stack.imgur.com/CpMMg.png" rel="noreferrer"><img src="https://i.stack.imgur.com/CpMMg.png" alt="enter image description here"></a></p>
  
  <p>3.
  <a href="https://i.stack.imgur.com/v4dwA.png" rel="noreferrer"><img src="https://i.stack.imgur.com/v4dwA.png" alt="enter image description here"></a></p>
  
  <p>I found a tutorial about this which provided by Microsoft:
  <a href="https://docs.microsoft.com/en-us/aspnet/core/migration/21-to-22?view=aspnetcore-2.2&amp;tabs=visual-studio" rel="noreferrer">https://docs.microsoft.com/en-us/aspnet/core/migration/21-to-22?view=aspnetcore-2.2&amp;tabs=visual-studio</a><br/><br/>
  I tried but still no work.<br/><br/>
  I think updating the new version SDK is easier like the .net framework by just changes the target framework in properties of the project. However, it seems not.<br/><br/>
  I wonder if there have an official tool which to update the .net core SDK from 2.1 to 2.2. Or I'd better create a brand new 2.2 project as well as paste all the file into it rather than fix the troublesome warnings.
  <br/><br/>
  Thank you.</p>