# System.InvalidOperationException: An error was generated for the query filter 'FilterName'. The filter expression must be a LambdaExpression that can be applied to the entity type 'EntityType'.

- **ID:** `dotnet/ef-core-query-filter-parameter-mismatch`
- **Domain:** dotnet
- **Category:** data_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Entity Framework Core query filter uses a parameterized expression that references a property or method not available on the entity's model, often due to a missing navigation property or incorrect lambda syntax.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 6.0 | active | — | — |
| 7.0 | active | — | — |
| 8.0 | active | — | — |
| 9.0 | active | — | — |

## Workarounds

1. **Rewrite the query filter in OnModelCreating to use a simple lambda without complex expressions. For example, change 'modelBuilder.Entity<Blog>().HasQueryFilter(b => b.TenantId == _tenantProvider.GetTenantId())' to 'modelBuilder.Entity<Blog>().HasQueryFilter(b => b.TenantId == 1)' and pass the tenant ID via a constructor parameter.** (85% success)
   ```
   Rewrite the query filter in OnModelCreating to use a simple lambda without complex expressions. For example, change 'modelBuilder.Entity<Blog>().HasQueryFilter(b => b.TenantId == _tenantProvider.GetTenantId())' to 'modelBuilder.Entity<Blog>().HasQueryFilter(b => b.TenantId == 1)' and pass the tenant ID via a constructor parameter.
   ```
2. **Ensure that any method used in the filter is a static method or property accessible at the model level. Replace instance methods with static equivalents: 'b => b.IsDeleted == false' instead of 'b => _service.IsDeleted(b)'.** (80% success)
   ```
   Ensure that any method used in the filter is a static method or property accessible at the model level. Replace instance methods with static equivalents: 'b => b.IsDeleted == false' instead of 'b => _service.IsDeleted(b)'.
   ```

## Dead Ends

- **** — Removing the filter entirely may break business logic that requires soft-delete or multi-tenant isolation. (60% fail)
- **** — Adding .Include() to eager-load navigation properties does not fix the filter expression itself; the filter must be corrected at the model level. (80% fail)
- **** — Changing the entity's base class or interface does not address the lambda parameter mismatch; the filter must be rewritten. (70% fail)