The Error

System.InvalidOperationException: The model has pending changes. Add a new migration or remove existing migrations.

Quick Fix - 1 Minute

# Package Manager Console
Add-Migration AddUserPhoneNumber
Update-Database
Or CLI
dotnet ef migrations add AddUserPhoneNumber
dotnet ef database update

Why This Happens

You changed DbContext or entity classes but didn't create a migration. EF detects model ≠ database schema at startup and throws. Happens after adding properties, DbSet, or changing types.

Best Practice for.NET 8

1. Check what changed: dotnet ef migrations has-pending-model-changes
2. If intentional: Add-Migration NameHere
3. If mistake: Revert model changes or Remove-Migration
4. Prod: Never auto-migrate. Generate SQL: dotnet ef migrations script

Related Dev Fixes

• Nullable Reference Warning Fix
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