Since SharePoint maintains its files and modification history, it is necessary to perform the following steps to delete/upgrade the deployed Web Parts with DevExpress controls and modified SharePoint Pages.
If you have previously modified certain SharePoint Pages directly using the SharePoint Designer, then edit the corresponding page with the SharePoint Designer in Advanced Mode, and comment out the DevExpress Register directives and control markup using the <%--…--%> expression.
Remove Web Parts that use DevExpress controls from all pages.
1) Edit the corresponding page using the Site Action -> Edit Page command.
2) Select the required Web Part.
3) Click the Delete command within the Smart Tag menu.
Remove all Web Parts from the Site Actions -> Site Settings -> Galleries -> Web Parts menu.
Make sure that there are no DevExpress entries in the Web.config file.
Clear the corresponding "Temporary ASP.NET Files" directory (the c:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\ for SharePoint 2013 and SharePoint 2016). This may require stopping the IIS process using the following command.
Restart the IIS using the following command.
Examine the problematic pages, and check to see if they operate properly and that there are no errors or warning messages.
If you have modified certain SharePoint Pages directly, then edit the corresponding page using the SharePoint Designer in Advanced Mode: remove comment expressions from the DevExpress Register directives and control markup, and update the DevExpress Register directives according to the new DevExpress version.
Upgrade the source folder of Web Part projects that use DevExpress controls using the Project Converter tool. See the Upgrade Notes help topic for more information.
Remove the Properties -> licenses.licx file, the Bin folder and the Obj folders.
Rebuild and redeploy the upgraded Web Parts projects.
Insert the required Web Part into the required page.
Examine the problematic pages and check to see if they operate properly, and that there are no errors or warning messages.