> For the complete documentation index, see [llms.txt](https://docs.eiffel.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.eiffel.dev/features/cross-cutting-concerns/api-response-consistency.md).

# API response consistency

The `ApiResponseFilter` is an action filter attribute that provides consistent structure to API responses. It wraps the API response body within an `ApiResponse` class.

```csharp
/// <summary>
/// Api response
/// </summary>
public class ApiResponse
{
    /// <summary>
    /// Error messages
    /// </summary>
    public string[]? Errors { get; init; }

    /// <summary>
    /// Success flag
    /// </summary>
    public bool IsSuccess { get; init; }

    /// <summary>
    /// Response body
    /// </summary>
    public object? Data { get; init; }

    /// <summary>
    /// Status code
    /// </summary>
    public HttpStatusCode StatusCode { get; init; }
}
```

#### Model Validation

If the model state is invalid, the filter captures the errors and returns a structured error response with an HTTP status code of `400 Bad Request`.

#### Installation

```bash
dotnet add package Eiffel.CrossCutting.ApiResponseConsistency
```

You should install **Eiffel.CrossCutting.ApiResponseConsistency** NuGet package into your application.&#x20;

#### Usage

To apply this filter, decorate your controllers or actions with `[ApiResponseFilter]`.

{% hint style="info" %}
For better experience decorate your metho&#x64;**`ProducesDefaultResponseType`**&#x61;nd **`ProducesResponseType`**&#x62;y using **ApiResponse** and **ApiResponse\<T>** classes.
{% endhint %}

```csharp
[ApiResponseFilter]
public class BookingController : ControllerBase
{
    [HttpPost]
    [ProducesDefaultResponseType(typeof(ApiResponse))]
    [ProducesResponseType(StatusCodes.Status200OK, Type = typeof(ApiResponse<CreateBookingResponse>))]
    public async Task<CreateBookingResponse> PostAsync([FromBody] CreateBookingRequest request)
    {
        // Your implementation details..
    }
}
```

To appy this filter to all controllers in your application, add to Mvc filters.

```csharp
// Program.cs (.NET5 and above)
public static async Task Main(string[] args)
{
    var builder = WebApplication.CreateBuilder(args);
    
    // Applies api response filter for all controllers
    builder.Services.AddControllers(options =>
    {
        options.Filters.Add<ApiResponseFilter>();
    });
     
    var app = builder.Build();
    app.Run();
}
```

**Disabling consistency for specific actions/controllers**

If you don't want a particular action or controller to be wrapped with this consistency logic, decorate it with the `DisableApiResponseConsistency` attribute.

```csharp
[DisableApiResponseConsistency]
public class FileController : ControllerBase
{
    [HttpPost]
    public async Task PostAsync(IFormFile file)
    {
        // Your implementation details..
    }
}
```