CoreOne.ModelPatch 1.4.0

CoreOne.ModelPatch

A powerful .NET 9 / .NET 10 library for applying partial updates (PATCH operations) to EF Core entities. It converts partial model data into Delta<T> objects and intelligently patches entities while handling nested relationships, unique constraints, and parent-child foreign key relationships.

Perfect for RESTful APIs, microservices, and any scenario requiring partial entity updates without manual property-by-property mapping.

🚀 Key Features

• Selective Property Updates - Only update properties present in the delta, ignoring missing fields
• Nested Relationship Handling - Automatically processes parent-child relationships with foreign key injection
• Unique Constraint Support - Respects [Index(IsUnique = true)] attributes (updates existing records instead of duplicating)
• Transaction Management - Wraps all operations in EF Core transactions with automatic rollback on errors
• Composite Key Support - Handles entities with single or composite primary keys
• Case-Insensitive Delta Properties - Property name matching is case-insensitive for flexibility
• Built-In JSON Naming Helpers - Configure Newtonsoft.Json or System.Text.Json property names without hand-written reflection lambdas
• Custom Property Name Mapping - Support custom property name resolution through ModelOptions.NameResolver
• Strict Field Validation (Optional) - Fail fast on unknown delta fields to catch typos early
• Optimistic Concurrency (Optional) - Validate [Timestamp] and [ConcurrencyCheck] tokens during updates
• Automatic Key Generation - Generates primary keys when missing (GUID by default, extensible via IKeyGenerator)
• Type-Safe Delta Operations - Strongly-typed Delta<T> with compile-time safety
• DTO-Friendly Delta Mapping - Map request DTOs into Delta<TEntity> with explicit field selection
• Rich Patch Results - PatchResult exposes Created, Updated, Unchanged, Items, and Get<T>()

📦 Installation

Install via NuGet:

dotnet add package CoreOne.ModelPatch

Or via the NuGet Package Manager:

Install-Package CoreOne.ModelPatch

Requirements:

• net9.0 or net10.0
• EF Core 9.0.x on net9.0, EF Core 10.0.x on net10.0
• CoreOne 1.4.0.3 (automatically installed as dependency)

🏗️ Setup

1. Register Services in DI Container

// In Program.cs or Startup.cs
services.AddDbContext<YourDbContext>(options => 
    options.UseSqlServer(connectionString));

services.AddModelPatch(options => {
    options.UseJsonPropertyNames();
    options.StrictPropertyMatching = true; // optional fail-fast mode
});

2. Inject into Your Services/Controllers

public class YourController : ControllerBase
{
    private readonly IDataModelService<YourDbContext> _dataService;

    public YourController(IDataModelService<YourDbContext> dataService)
    {
        _dataService = dataService;
    }
    
    // ... use _dataService in your endpoints
}

🛠️ Usage Examples

Basic PATCH Operation

// Your entity model
public class User
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public string? PhoneNumber { get; set; }
}

// Create a partial update model
var userUpdate = new User {
    Id = existingUserId,
    Name = "John Doe",
    Email = "john@example.com"
};

// Apply the patch directly and optionally exclude fields from the generated delta
var result = await _dataService.Patch(userUpdate, delta => {
    delta.Remove(nameof(User.PhoneNumber));
}, cancellationToken);

if (result.ResultType == ResultType.Success)
{
    var updated = result.Updated;
    Console.WriteLine($"Updated {updated} records");
}

Parent-Child Relationships

The library automatically handles nested relationships:

public class Blog
{
    [Key] public Guid BlogId { get; set; }
    [Required] public string Name { get; set; }
    
    [InverseProperty(nameof(Tag.Blog))]
    public List<Tag> Tags { get; init; } = [];
}

[Index(nameof(Name), IsUnique = true)]
public class Tag
{
    [Key] public Guid Id { get; set; }
    public string Name { get; set; }
    
    public Guid? BlogId { get; set; }
    [ForeignKey(nameof(BlogId))]
    public Blog? Blog { get; set; }
}

// Create blog with nested tags
var blog = new Blog {
    BlogId = Guid.NewGuid(),
    Name = "Tech Blog",
    Tags = [
        new Tag { Name = "CSharp" },
        new Tag { Name = "DotNet" },
        new Tag { Name = "CSharp" } // Duplicate - will update existing due to unique index
    ]
};

var result = await _dataService.Patch(blog, cancellationToken);

// The library will:
// 1. Insert/update the Blog
// 2. Process each Tag
// 3. Automatically set BlogId foreign key in each Tag
// 4. Respect unique index (only 2 tags created: CSharp and DotNet)

Unique Index Constraint Handling

When entities have unique indexes, the library updates existing records instead of creating duplicates:

[Index(nameof(Email), IsUnique = true)]
public class User
{
    public Guid Id { get; set; }
    public string Email { get; set; }
    public string Name { get; set; }
}

// If a user with email "john@example.com" already exists:
var newUser = new User {
    Email = "john@example.com",
    Name = "John Updated"
};

var result = await _dataService.Patch(newUser, cancellationToken);

// Instead of throwing a duplicate key error, the existing user is updated
var updated = result.Get<User>().FirstOrDefault();

Multiple Models (Collection Patching)

// Patch multiple models of the same type directly
var users = new List<User> {
    new User { Id = id1, Name = "Alice" },
    new User { Id = id2, Name = "Bob" }
};

var result = await _dataService.Patch(users, cancellationToken);

// Or patch mixed model types
var mixedModels = new List<object> { user1, blog1, tag1 };
var result = await _dataService.PatchCollection(mixedModels, cancellationToken);

DTO-First PATCH Mapping

public class UpdateBlogRequest
{
    public Guid BlogId { get; set; }
    public string? Name { get; set; }
    public string? Url { get; set; }
    public string? IgnoredByPatch { get; set; }
}

var request = new UpdateBlogRequest {
    BlogId = blogId,
    Name = "Updated title",
    Url = "https://example.com"
};

// Keep only the target entity fields you want to patch
var delta = request.ToDelta<Blog>(p => p.BlogId, p => p.Name, p => p.Url);
var result = await _dataService.Patch(delta, cancellationToken);

// Or patch DTO directly with target entity type
var directResult = await _dataService.Patch<Blog, UpdateBlogRequest>(request, cancellationToken);

// Note: direct DTO patch maps DTO fields into a delta by matching names.
// Use the explicit include-list overload when you want strict field allow-listing.
var safeResult = await _dataService.Patch<Blog, UpdateBlogRequest>(
    request,
    [p => p.BlogId, p => p.Name, p => p.Url],
    cancellationToken);

Optimistic Concurrency Example

public class Blog
{
    [Key] public Guid BlogId { get; set; }
    public string Name { get; set; } = string.Empty;

    [Timestamp]
    public byte[] RowVersion { get; set; } = [];
}

services.AddModelPatch(options => {
    options.ValidateConcurrencyTokens = true;
    options.RequireConcurrencyTokenForUpdates = true; // optional stricter mode
});

var delta = new Delta<Blog> {
    [nameof(Blog.BlogId)] = blogId,
    [nameof(Blog.Name)] = "Updated",
    [nameof(Blog.RowVersion)] = Convert.ToBase64String(rowVersionFromClient)
};

var result = await _dataService.Patch(delta, cancellationToken);
// Fails with ResultType.Fail when token is stale or missing (if required)

🌐 ASP.NET Core Web API Integration

PATCH Endpoint Example

[ApiController]
[Route("api/[controller]")]
public class BlogsController : ControllerBase
{
    private readonly IDataModelService<AppDbContext> _dataService;

    public BlogsController(IDataModelService<AppDbContext> dataService)
    {
        _dataService = dataService;
    }

    [HttpPatch("{id}")]
    public async Task<IActionResult> PatchBlog(
        Guid id, 
        [FromBody] Blog patchData, 
        CancellationToken cancellationToken)
    {
        // Ensure the ID matches
        patchData.BlogId = id;
        
        var result = await _dataService.Patch(patchData, cancellationToken);

        if (result.ResultType == ResultType.Success)
        {
            return Ok(new {
                message = "Blog updated successfully",
                created = result.Created,
                updated = result.Updated,
                items = result.Items
            });
        }

        return BadRequest(new { 
            error = result.Message 
        });
    }

    [HttpPatch("bulk")]
    public async Task<IActionResult> PatchMultipleBlogs(
        [FromBody] List<Blog> blogs, 
        CancellationToken cancellationToken)
    {
        var result = await _dataService.Patch(blogs, cancellationToken);

        if (result.ResultType == ResultType.Success)
        {
            var stats = new {
                created = result.Created,
                updated = result.Updated,
                unchanged = result.Unchanged
            };
            return Ok(new { message = "Bulk update completed", stats });
        }

        return BadRequest(new { error = result.Message });
    }
}

Handling Validation Errors

The library automatically rolls back transactions when validation fails:

public class Blog
{
    [Key] public Guid BlogId { get; set; }
    
    [Required, StringLength(50)] 
    public string Name { get; set; }
    
    [Url, StringLength(200)] 
    public string? Url { get; set; }
}

// If validation fails (e.g., Name exceeds 50 chars), 
// the entire transaction is rolled back automatically
var result = await _dataService.Patch(delta, cancellationToken);

if (result.ResultType == ResultType.Fail)
{
    // Handle validation error
    return BadRequest(result.Message);
}

🔧 Advanced Configuration

Built-In JSON Property Name Helpers

Use the built-in helpers when your models already declare JSON names:

services.Configure<ModelOptions>(options => {
    options.UseNewtonsoftJsonPropertyNames();
    // or options.UseSystemTextJsonPropertyNames();
    // or options.UseJsonPropertyNames(); // supports both attribute types
});

// Example entity with JSON property mapping
public class Tag
{
    [Key] public Guid Id { get; set; }
    
    [JsonProperty("tag_name")]  // Maps "tag_name" in JSON to Name property
    public string Name { get; set; }
}

// Now you can use either property name in your delta
var delta = new Delta<Tag> {
    ["tag_name"] = "CSharp",  // Works!
    ["Name"] = "CSharp"        // Also works! (case-insensitive)
};

You can still provide a custom NameResolver when you need non-attribute-based naming.

Default Options

ModelOptions defaults are:

• StrictPropertyMatching = false
• ValidateConcurrencyTokens = true
• RequireConcurrencyTokenForUpdates = false
• KeyGenerator = GuidGenerator (creates version 7 GUID keys wrapped in KeyModel)

Strict Field Validation

services.AddModelPatch(options => {
    options.StrictPropertyMatching = true;
});

// Unknown fields will fail with a clear message instead of being ignored.

Working with PatchResult

The Patch methods return PatchResult, which provides summary counts and typed access to processed entities:

var result = await _dataService.Patch(delta, cancellationToken);

if (result.ResultType == ResultType.Success)
{
    var created = result.Created;
    var updated = result.Updated;
    var unchanged = result.Unchanged;
    var blogs = result.Get<Blog>();
    var newTags = result.Get<Tag>(p => p.CrudType == CrudType.Created);
}

Custom Key Generation

Implement IKeyGenerator for custom primary key generation:

public class CustomKeyGenerator : IKeyGenerator
{
    public KeyModel Create() => KeyModel.Create(Guid.CreateVersion7());
}

services.Configure<ModelOptions>(options => {
    options.KeyGenerator = new CustomKeyGenerator();
});

Strongly Typed IDs (ICoreId<T>)

AddModelPatch(...) also registers an open generic IKeyGenerator<TKey> implementation (StronglyTypedIdGenerator<TKey>), which can be used for strongly typed IDs backed by GUID values.

[StronglyTypedId<Guid>]
public readonly partial struct NoteId : ICoreId<NoteId>
{
}

// Example custom generator for NoteId
public sealed class NoteIdKeyGenerator : IKeyGenerator<NoteId>
{
    public KeyModel Create() => KeyModel.Create(NoteId.Create());
}

For runtime patching, the built-in primary-key auto-generation path currently targets Guid/Guid? key properties. For other key property types, include the key value in the incoming delta/model payload or provide a custom patch pipeline.

🎯 How It Works

The Delta Pattern

Delta is a case-insensitive dictionary that holds partial model data:

// Delta inherits from Data<string, object> (case-insensitive dictionary)
var delta = new Delta<User> {
    ["name"] = "John",      // Case-insensitive
    ["Name"] = "John",      // Same as above
    ["EMAIL"] = "john@example.com"
};

// Or convert from model
var user = new User { Name = "John", Email = "john@example.com" };
var delta = user.ToDelta();

// Or map from a DTO into an entity delta
var request = new { blogId = blogId, name = "Updated title", url = "https://example.com" };
var blogDelta = request.ToDelta<Blog>(nameof(Blog.BlogId), nameof(Blog.Name), nameof(Blog.Url));

// Remove unwanted properties
delta.Remove("CreatedAt");
delta.Remove("UpdatedAt");

Processing Workflow

1. Delta Conversion - Convert your model to Delta<T> using .ToDelta()
2. Transaction Begin - Library wraps operation in EF Core transaction
3. Entity Resolution - Finds existing entities by primary/unique keys
4. Property Patching - Updates only properties present in delta
5. Relationship Processing - Recursively processes child collections
6. Foreign Key Injection - Automatically sets parent foreign keys in children
7. Unique Constraint Handling - Updates existing records with unique values
8. Validation - EF Core validates changes
9. Transaction Commit - Saves all changes atomically (or rolls back on error)

Relationship Discovery

The library uses reflection and EF Core attributes to discover relationships:

• [InverseProperty] - Links parent to child collections
• [ForeignKey] - Identifies foreign key properties
• Convention-based - Falls back to {ParentName}Id pattern

public class Blog
{
    [Key] public Guid BlogId { get; set; }
    
    // InverseProperty tells the library where this collection is referenced
    [InverseProperty(nameof(Post.Blog))]
    public List<Post> Posts { get; init; } = [];
}

public class Post
{
    [Key] public Guid Id { get; set; }
    
    // ForeignKey identifies the foreign key property
    public Guid? BlogId { get; set; }
    [ForeignKey(nameof(BlogId))]
    public Blog? Blog { get; set; }
}

📋 API Reference

IDataModelService<TContext>

Main service contract for processing patches.

Interface Methods

// Patch a single typed delta
Task<PatchResult> Patch<T>(
    Delta<T> delta, 
    CancellationToken cancellationToken = default) where T : class, new()

// Patch multiple deltas of the same type
Task<PatchResult> Patch<T>(
    DeltaCollection<T> items, 
    CancellationToken cancellationToken = default) where T : class, new()

// Patch mixed model types
Task<PatchResult> PatchCollection(
    IEnumerable<object?> items, 
    CancellationToken cancellationToken = default)

Extension Patch Methods

The following overloads are extension methods on IDataModelService<TContext> (from DataModelServiceExtensions):

// Patch a single model directly
Task<PatchResult> Patch<TContext, TModel>(
    this IDataModelService<TContext> service,
    TModel model,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TModel : class, new()

// Patch a single model directly and customize generated delta
Task<PatchResult> Patch<TContext, TModel>(
    this IDataModelService<TContext> service,
    TModel model,
    Action<Delta<TModel>> configure,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TModel : class, new()

// Patch a DTO into a target entity
Task<PatchResult> Patch<TContext, TEntity, TDto>(
    this IDataModelService<TContext> service,
    TDto? dto,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TEntity : class, new()

// Patch DTO with delta customization callback
Task<PatchResult> Patch<TContext, TEntity, TDto>(
    this IDataModelService<TContext> service,
    TDto? dto,
    Action<Delta<TEntity>> configure,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TEntity : class, new()

// Patch DTO with explicit included entity properties
Task<PatchResult> Patch<TContext, TEntity, TDto>(
    this IDataModelService<TContext> service,
    TDto? dto,
    IEnumerable<Expression<Func<TEntity, object?>>> includedProperties,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TEntity : class, new()

// Patch a collection of model instances directly
Task<PatchResult> Patch<TContext, TModel>(
    this IDataModelService<TContext> service,
    IEnumerable<TModel?> items,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TModel : class, new()

// Patch a collection of model instances directly with delta customization
Task<PatchResult> Patch<TContext, TModel>(
    this IDataModelService<TContext> service,
    IEnumerable<TModel?> items,
    Action<Delta<TModel>> configure,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TModel : class, new()

// Patch a collection of DTO payloads
Task<PatchResult> Patch<TContext, TEntity, TDto>(
    this IDataModelService<TContext> service,
    IEnumerable<TDto?> items,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TEntity : class, new()

// Patch a collection of DTO payloads with explicit included entity properties
Task<PatchResult> Patch<TContext, TEntity, TDto>(
    this IDataModelService<TContext> service,
    IEnumerable<TDto?> items,
    IEnumerable<Expression<Func<TEntity, object?>>> includedProperties,
    CancellationToken cancellationToken = default)
    where TContext : DbContext where TEntity : class, new()

Extension Methods

// Convert model to Delta<T>
Delta<T> ToDelta<T>(this T model) where T : class, new()

// Convert collection to DeltaCollection<T>
DeltaCollection<T> ToDeltaCollection<T>(this IEnumerable<T?> items) where T : class, new()

// Map a DTO into a target entity delta
Delta<TEntity> ToDelta<TEntity>(this object model) where TEntity : class, new()

// Map a DTO into a target entity delta using an explicit field list
Delta<TEntity> ToDelta<TEntity>(this object model, params string[] includedFields) where TEntity : class, new()

// Map a DTO into a target entity delta using entity property expressions
Delta<TEntity> ToDelta<TEntity>(this object model, params Expression<Func<TEntity, object?>>[] includedProperties) where TEntity : class, new()

// Filter a patch result
IEnumerable<T> Get<T>(Predicate<ModelState>? predicate = null)
int Count(Predicate<ModelState>? predicate = null)

CrudType Enum

Indicates what operation was performed:

public enum CrudType
{
    Created = 1,
    Read = 2,
    Updated = 4,
    Deleted = 8
}

⚠️ Important Notes

Transaction Behavior

• All operations are wrapped in transactions
• Validation failures automatically rollback the entire transaction
• Nested operations are part of the same transaction
• Use cancellation tokens to cancel long-running operations

Performance Considerations

• The library uses reflection and caches metadata for performance
• Composite keys and unique indexes are discovered once per type
• For bulk operations, use DeltaCollection<T> or PatchCollection instead of individual calls

Limitations

• Entities must have parameterless constructors
• Navigation properties must be settable (at least init accessors)
• Circular references in object graphs may cause issues (design your models carefully)
• Currently supports INSERT and UPDATE operations (DELETE planned for future)

🧰 Troubleshooting Cookbook

1) Strict mode fails with unknown field errors

Symptom

• ResultType.Fail with a message similar to: Unknown fields for Blog: does_not_exist

Likely cause

• StrictPropertyMatching is enabled and the incoming payload contains fields that do not map to the target entity.
• The payload uses DTO names that differ from entity names without JSON name mapping.

Fix

services.AddModelPatch(options => {
    options.StrictPropertyMatching = true;
    options.UseJsonPropertyNames(); // if your model uses JsonProperty/JsonPropertyName
});

// Option A: send only entity field names
var delta = new Delta<Blog> {
    [nameof(Blog.BlogId)] = id,
    [nameof(Blog.Name)] = "Updated"
};

// Option B: map DTO to entity delta with explicit include list
var deltaFromDto = request.ToDelta<Blog>(p => p.BlogId, p => p.Name, p => p.Url);

2) Concurrency mismatch on update

Symptom

• ResultType.Fail with a message similar to: Concurrency token mismatch for Blog.RowVersion

Likely cause

• The client is sending an outdated token value for a model using [Timestamp] or [ConcurrencyCheck].

Fix

services.AddModelPatch(options => {
    options.ValidateConcurrencyTokens = true;
    options.RequireConcurrencyTokenForUpdates = true;
});

var delta = new Delta<Blog> {
    [nameof(Blog.BlogId)] = blogId,
    [nameof(Blog.Name)] = "Updated",
    [nameof(Blog.RowVersion)] = Convert.ToBase64String(currentRowVersionFromClient)
};

var result = await dataService.Patch(delta, token);

3) Update fails because concurrency token is required

Symptom

• ResultType.Fail with a message similar to: Concurrency token is required for updates to Blog

Likely cause

• RequireConcurrencyTokenForUpdates is enabled for a model that has concurrency tokens, but the payload omitted the token.

Fix

• Include token values on update requests for concurrency-enabled models.
• If your API does not require this strict behavior, set RequireConcurrencyTokenForUpdates = false.

4) DTO patch updates missing or wrong fields

Symptom

• Patch succeeds but expected fields are unchanged, or wrong fields are updated.

Likely cause

• DTO property names don’t match entity names.
• DTO includes fields that should not be patched.

Fix

// Recommended: target entity + explicit allowed fields
var result = await dataService.Patch<Blog, UpdateBlogRequest>(
    request,
    [p => p.BlogId, p => p.Name, p => p.Url],
    token);

// Alternative: generate delta then trim
var delta = request.ToDelta<Blog>(p => p.BlogId, p => p.Name, p => p.Url);
var patchResult = await dataService.Patch(delta, token);

5) Unique index behavior seems unexpected (update vs insert)

Symptom

• Sending a new object appears to update an existing row instead of inserting a new one.

Likely cause

• Target entity has a unique index ([Index(..., IsUnique = true)]), and an existing row already matches the unique key.

Fix

• This is expected behavior for duplicate unique-key payloads.
• If insert-only semantics are required for a flow, validate uniqueness before calling Patch or use a dedicated insert endpoint.

Quick triage checklist

• Confirm target entity key and unique index values in the payload.
• Confirm DTO-to-entity field mapping (UseJsonPropertyNames or explicit include list).
• Confirm strict mode and concurrency options in AddModelPatch(...).
• Inspect result.Message, result.Created, result.Updated, result.Unchanged, and result.Get<T>().

⬆️ Upgrade Notes

Current 1.4.0 Notes

• IKeyGenerator.Create() now returns KeyModel.
• IKeyGenerator<TKey> support is available for strongly typed key scenarios.
• AddModelPatch(...) registers IDataModelService<TContext>, IKeyGenerator, and open-generic IKeyGenerator<TKey>.
• Concurrency token validation options (ValidateConcurrencyTokens, RequireConcurrencyTokenForUpdates) are part of ModelOptions.

🧪 Testing

The library includes comprehensive unit and integration tests:

# Run tests
dotnet test

# Run with coverage
dotnet test --collect:"XPlat Code Coverage"

See COVERAGE_REPORT.md for detailed coverage metrics.

📊 Test Coverage

• Unit and integration tests run against both net9.0 and net10.0
• Current suite covers direct patching, DTO mapping, JSON naming helpers, unique indexes, and parent-child processing

🔗 Dependencies

• CoreOne (1.4.0.3+) - Provides Data<TKey, TValue>, IResult<T>, reflection utilities
• Microsoft.EntityFrameworkCore 9.0.x / 10.0.x - EF Core framework matched to the target framework

🤝 Contributing

Contributions are welcome! Please:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Write tests for your changes
4. Ensure all tests pass (dotnet test)
5. Commit your changes (git commit -m 'Add amazing feature')
6. Push to the branch (git push origin feature/amazing-feature)
7. Open a Pull Request

🐛 Issues & Support

• GitHub Issues: https://github.com/jlopez788/CoreOne.ModelPatch/issues
• Documentation: See .github/copilot-instructions.md for AI-friendly development guide

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Built on top of CoreOne utility library
• Uses Entity Framework Core for data access
• Inspired by JSON Patch (RFC 6902) but adapted for EF Core entities

---

Author: Juan Lopez
Version: 1.4.0 Target Frameworks: net9.0, net10.0