LinqAPI

LinqAPI is a dynamic and generic API generator for ASP.NET Core that leverages LINQ-based filtering, paging, and CRUD operations. It provides a set of reusable controllers, services, and repository implementations to reduce boilerplate code and streamline API development by automatically mapping between your entities and DTOs.

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Table of Contents

• Features
• Introduction
• Getting Started
  • Prerequisites
  • Installation
  • DI Registration
• Usage
  • Creating Your API Controllers
  • Automatic Mapping
  • Filtering and Paging
• Demo Project
• Testing
• Contributing
• License
• Acknowledgements

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Features

• Dynamic CRUD Operations: Automatically handles common CRUD operations.
• LINQ-Based Filtering & Paging: Supports dynamic filtering using LINQ expressions and returns paginated results.
• Automatic Mapping: Uses AutoMapper with a dynamic mapping profile to map between your entities and DTOs without manual configuration.
• Generic & Extensible: Works with any entity/DTO pair that derives from BaseEntity<TId> and BaseDto<TId>.
• DI Registration Helper: Simplifies dependency injection configuration via a single extension method (builder.Services.AddLinqApi<DbContext>()).

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Getting Started

Prerequisites

• .NET 8 SDK
• ASP.NET Core (for building Web APIs)
• Entity Framework Core (for data access)
• AutoMapper (for object mapping)
• Optional: Microsoft.EntityFrameworkCore.InMemory for demo or testing purposes

Installation

You can add LinqAPI to your project via NuGet:

dotnet add package LinqAPI

Or, if you're developing it locally, clone the repository and add it as a project reference.

DI Registration

LinqAPI provides an extension method to simplify DI registration. In your Program.cs (or Startup.cs), add:

using LinqAPI;

var builder = WebApplication.CreateBuilder(args);

// Register your DbContext
builder.Services.AddDbContext<DemoDbContext>(options =>
    options.UseInMemoryDatabase("DemoDb"));

// Register LinqAPI dependencies, including repository, service, and automatic mapping
builder.Services.AddLinqApi<DemoDbContext>();

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();

app.Run();

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Filtering and Paging

LinqAPI provides powerful filtering and paging capabilities using dynamic LINQ queries. You can perform filtering using expressions such as StartsWith, EndsWith, Contains, and logical operators like and, or, >, <, >=, <=.

Example Request for filterpaged Endpoint

{
  "filter": "name.StartsWith(\"Product C\")",
  "pager": {
    "pageNumber": 1,
    "pageSize": 50
  },
  "orderby": "id",
  "desc": true
}

How Filtering Works

The filter field is a dynamic LINQ expression that is executed against the database.

• StartsWith("value") – Matches strings that start with the given value.
• EndsWith("value") – Matches strings that end with the given value.
• Contains("value") – Matches strings that contain the given value.
• > < >= <= – Comparison operators.
• and, or – Logical operators.
• 1=1 – Used to retrieve all records without filtering.

Example Queries:

Retrieve products where price is greater than 20 and name contains "Product":

{
  "filter": "price > 20 and name.Contains(\"Product\")"
}

Retrieve items where ID is less than 5 or the name starts with "Item":

{
  "filter": "id < 5 or name.StartsWith(\"Item\")"
}

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Paging System

Paging is controlled using the Pager class:

public class Pager
{
    private int _pageNumber = 1;
    private int _pageSize = 50;

    public int PageNumber
    {
        get => _pageNumber;
        set => _pageNumber = value < 1 ? 1 : value > int.MaxValue ? int.MaxValue : value;
    }

    public int PageSize
    {
        get => _pageSize;
        set => _pageSize = value < 1 ? 1 : value > 500 ? 500 : value;
    }
}

• PageNumber: Defines the current page (default = 1).
• PageSize: Defines the number of results per page (min = 1, max = 500).

Retrieve all records without filtering:

{
  "filter": "1=1",
  "pager": {
    "pageNumber": 1,
    "pageSize": 50
  }
}

Sorting with orderby & desc

• orderby: The property name to sort results by.
• desc: Boolean flag for descending order (true for descending, false for ascending).

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Including Navigation Properties

The Includes field allows eager loading of related navigation properties.

public class LinqFilterModel
{
    public string Filter { get; set; }
    public Pager Pager { get; set; }
    public List<string> Includes { get; set; }
    public string Orderby { get; set; }
    public bool Desc { get; set; }
}

Example Request with Includes:

{
  "filter": "1=1",
  "pager": {
    "pageNumber": 1,
    "pageSize": 50
  },
  "includes": ["Category", "Supplier"]
}

This will include Category and Supplier navigation properties in the response.

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Conclusion

LinqAPI simplifies API development by providing automated filtering, paging, and sorting using LINQ expressions. With minimal setup, you can create powerful, dynamic APIs.

For any issues, feature requests, or questions, please open an issue in the repository or contact the maintainers.

Happy coding! 🚀