🎯 JsonPatchBind

✨ A lightweight library for handling partial updates in ASP.NET Core APIs without JSON Patch.

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📖 Description

When building APIs for partial updates (PATCH requests), developers often face challenges such as:

• 🧩 Differentiating between an explicit null and an omitted field
• 🛡️ Avoiding overwriting fields that weren't sent by the client
• 📚 Ensuring accurate schema documentation with Swagger/Swashbuckle

JsonPatchBind elegantly solves these problems using the Optional<T> type!

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🌟 Key Benefits

• Field Presence Tracking - Know if a property was included (even if null)
• Safe Updates - Only modify fields provided in the request
• Native JSON Support - Works seamlessly with System.Text.Json
• Swagger Ready - Automatic schema generation for Optional<T>

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🚀 Features

Feature	Description
Optional<T> Wrapper	HasValue = true → Field was sent (value can be null)
Custom JSON Converter	Handles serialization/deserialization perfectly
Swagger Schema Filter	Shows Optional<T> as nullable fields in docs
ASP.NET Core Integration	Works with [FromBody] out of the box
Zero Dependencies	Pure .NET solution

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❓ Why Not JSON Patch?

While JSON Patch (RFC 6902) is standard, it has drawbacks:

Issue	JsonPatchBind	JSON Patch
Payload Complexity	Simple JSON	Complex operations
Null Handling	Clear differentiation	Ambiguous
Swagger Support	Automatic	Manual config needed
Validation	Minimal	Extensive

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⚖️ Comparison Table

When to Use Which?

Criteria	JsonPatchBind ✅	JSON Patch ❌
Simple updates	Perfect fit	Overkill
Client simplicity	Easy JSON	Complex ops
Field tracking	Built-in	Not native
Swagger integration	Auto-magic	Manual work

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🔧 Installation

1. Add the NuGet package:

   dotnet add package JsonPatchBind

2. Configure Services:

   builder.Services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.Converters.Add(new OptionalConverterFactory());
    });

3. Add Swagger Support:

   builder.Services.AddSwaggerGen(c =>
   {
    c.SchemaFilter<OptionalSchemaFilter>();
   });

🎮 Usage Example

Model definition:

   public class UserDto
   {
    public int Id { get; set; }

    public string Name { get; set; }
    
    [ValidateOptional(typeof(StringLengthAttribute), 32)]
    [ValidateOptional(typeof(RegularExpressionAttribute), "\\d+")]
    public Optional<string> SurName { get; set; }
    
    public Optional<int> Age { get; set; }
    
    public Optional<AddressDto> Address { get; set; }

   }

Controller:

[HttpPatch("{id}")]
public IActionResult UpdateUser(int id, [FromBody] UserDto user)
{
    // Only update fields that were actually sent
    if (user.SurName.HasValue)
    {
        // Handle surname update
    }
}