Upgrade the framework from 3.5 to 4.8 and SharePoint 2010 to SharePoint 2019.

1. Pre-upgrade preparation
 System Requirements Verification
Hardware:
64-bit CPU, ≥12GB RAM (16GB+ recommended)
Storage: ≥80GB system disk space + additional database space
Software:
Windows Server 2016/2019
SQL Server 2016/2017/2019
NET Framework 4.8
 Backup of critical data
Content database:
powershell
Backup-SPSite -Identity <SiteURL> -Path C:\Backup\site.bak
Customized solution: Manually backup WSP packages and code
2. Phased Upgrade Procedure
 Phase 1: Migrate to an intermediate version (SharePoint 2013/2016)
Create a new SharePoint 2013/2016 farm
Upgrade using Database Append:
powershell
Mount-SPContentDatabase -Name <DBName> -WebApplication <TargetWebApp>
Test for functional compatibility
 Phase 2: Upgrading to SharePoint 2019
Install SharePoint 2019 Prerequisites:
powershell
Install-WindowsFeature NET-Framework-Features, Web-Server, WAS
Attach Content Database (same as step 1)
Stage 3: Migrate .NET Framework 3.5 → 4.8
Update custom code:
Recompile solution (target framework changed to 4.8)
Replace deprecated APIs (e.g. Microsoft.SharePoint.WebPartPages)
Modify web.config:
xml
<compilation targetFramework=“4.8” />
<httpRuntime targetFramework=“4.8” />
Run HTML
3. Key Notes
 Compatibility issues:
2010 workflows (SPD workflows) need to be migrated to Power Automate or Azure Logic Apps.
InfoPath forms need to be replaced with Power Apps.
Authentication Updates:
Classic Mode authentication needs to be migrated to Statement Based Authentication.
 Search Architecture:
2010 search configuration needs to be rebuilt in 2019
4. Validation and Optimization
Functional Test List:
 List of functional tests.
Customization of web parts and page layouts
User rights inheritance
 Performance Optimization:
Enable Blob caching:
xml
<BlobCache location=“C:\BlobCache” path="\. (gif|jpg|png)$“ maxSize=”10“ enabled=”true” />
Running HTML
Configuring the Distributed Cache Service