dynamic-schema-design

# Dynamic Schema Design with EF Core JSON Columns

Guidance for implementing flexible content schemas using EF Core JSON columns, enabling dynamic custom fields without database migrations.

## When to Use This Skill

- Designing custom field storage for CMS content types
- Implementing dynamic properties that vary per content instance
- Avoiding frequent database migrations for schema changes
- Querying JSON data with LINQ in EF Core
- Planning indexing strategies for JSON columns
- Migrating from EAV (Entity-Attribute-Value) to JSON storage

## EF Core JSON Column Fundamentals

### Basic Configuration (.NET 10 / EF Core 10)

```csharp
// Entity with JSON-stored custom fields
public class ContentItem
{
    public Guid Id { get; set; }
    public string ContentType { get; set; } = string.Empty;
    public string Title { get; set; } = string.Empty;
    public DateTime CreatedUtc { get; set; }

    // JSON column for dynamic fields
    public CustomFieldsData CustomFields { get; set; } = new();
}

// Owned entity stored as JSON
public class CustomFieldsData
{
    public Dictionary<string, object?> Fields { get; set; } = new();
    public Dictionary<string, FieldMetadata> Metadata { get; set; } = new();
}

public class FieldMetadata
{
    public string FieldType { get; set; } = string.Empty;
    public bool IsRequired { get; set; }
    public string? DisplayName { get; set; }
}
```

### DbContext Configuration

```csharp
public class ContentDbContext : DbContext
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<ContentItem>(entity =>
        {
            entity.HasKey(e => e.Id);

            // Configure JSON column with ToJson()
            entity.OwnsOne(e => e.CustomFields, builder =>
            {
                builder.ToJson();
            });
        });
    }
}
```

## JSON Column Patterns

### Pattern 1: Typed Custom Fields

Best for when field schemas are known at compile time.

```csharp
// Strongly