AutoWrapper is a simple, yet customizable global exception handler and response wrapper for ASP.NET Core APIs. It uses an ASP.NET Core middleware to intercept incoming HTTP requests and automatically wraps the responses for you by providing a consistent response format for both successful and error results. The goal is to let you focus on your business specific requirements and let the wrapper automatically handle the HTTP response. This can speedup the development time when building your APIs while enforcing own standards for your HTTP responses.

AutoWrapper is a project fork based from VMD.RESTApiResponseWrapper.Core which is designed to support .NET Core 2.1, 2.2, 3.x and above. The implementation of this package was refactored to provide a more convenient way to use the middleware with added flexibility.

• Exception handling
• ModelState validation error handling (support both Data Annotation and FluentValidation)
• A configurable API exception
• A consistent response format for Result and Errors
• A detailed Result response
• A detailed Error response
• A configurable HTTP StatusCodes and messages
• Add support for Swagger
• Add Logging support for Request, Response and Exceptions
• A configurable middleware options to configure the wrapper.
• Enable property name mappings for the default ApiResponse properties.
• Add support for implementing your own user-defined Response and Error schema / object.
• Add support for ignoring action methods that don't need to be wrapped using [AutoWrapIgnore] filter attribute.
• Enable backwards compatibility support for netcoreapp2.1 and netcoreapp.2.2 .NET Core frameworks.

1. Download and Install the latest AutoWrapper.Core from NuGet or via CLI:

PM> Install-Package AutoWrapper.Core -Version 2.1.0

2. Declare the following namespace within Startup.cs

using AutoWrapper;

3. Register the middleware below within the Configure() method of Startup.cs "before" the UseRouting() middleware:

app.UseApiResponseAndExceptionWrapper();

That's simple! Here’s how the response is going to look like for the default ASP.NET Core API template “WeatherForecastController” API:

{
    "message": "Request successful.",
    "isError": false,
    "result": [
        {
            "date": "2019-09-16T23:37:51.5544349-05:00",
            "temperatureC": 21,
            "temperatureF": 69,
            "summary": "Mild"
        },
        {
            "date": "2019-09-17T23:37:51.554466-05:00",
            "temperatureC": 28,
            "temperatureF": 82,
            "summary": "Cool"
        },
        {
            "date": "2019-09-18T23:37:51.554467-05:00",
            "temperatureC": 21,
            "temperatureF": 69,
            "summary": "Sweltering"
        },
        {
            "date": "2019-09-19T23:37:51.5544676-05:00",
            "temperatureC": 53,
            "temperatureF": 127,
            "summary": "Chilly"
        },
        {
            "date": "2019-09-20T23:37:51.5544681-05:00",
            "temperatureC": 22,
            "temperatureF": 71,
            "summary": "Bracing"
        }
    ]
}

To display a custom message in your response, use the ApiResponse object from AutoWrapper.Wrappers namespace. For example, if you want to display a message when a successful POST has been made, then you can do something like this:

[HttpPost]
public async Task<ApiResponse> Post([FromBody]CreateBandDTO band)  
{
    //Call a method to add a new record to the database
    try
    {
        var result = await SampleData.AddNew(band);
        return new ApiResponse("New record has been created to the database", result, 201);
    }
    catch (Exception ex)
    {
        //TO DO: Log ex
        throw;
    }
}

Running the code will give you the following result when successful:

{
    "message": "New record has been created to the database",
    "isError": false,
    "result": 100
}

The ApiResponse object has the following parameters that you can set:

ApiResponse(string message, object result = null, int statusCode = 200, string apiVersion = "1.0.0.0")  

AutoWrapper also provides an ApiException object that you can use to define your own exception. For example, if you want to throw your own exception message, you could simply do:

throw new ApiException(ModelState.AllErrors());

throw new ApiException($"Record with id: {id} does not exist.", 400);

For example, let’s modify the POST method with ModelState validation:

[HttpPost]
public async Task<ApiResponse> Post([FromBody]CreateBandDTO band)
{
    if (ModelState.IsValid)
    {
        //Call a method to add a new record to the database
        try
        {
            var result = await SampleData.AddNew(band);
            return new ApiResponse("New record has been created to the database", result, 201);
        }
        catch (Exception ex)
        {
            //TO DO: Log ex
            throw;
        }
    }
    else
        throw new ApiException(ModelState.AllErrors());
}

Running the code will result to something like this when validation fails:

{
    "isError": true,
    "responseException": {
        "exceptionMessage": "Request responded with validation error(s). Please correct the specified validation errors and try again.",
        "validationErrors": [
            {
                "field": "Name",
                "message": "The Name field is required."
            }
        ]
    }
}

See how the validationErrors property is automatically populated with the violated fields from your model.

The ApiException object contains the following overload constructors that you can use to define an exception:

ApiException(string message, int statusCode = 500, string errorCode = "", string refLink = "")
ApiException(IEnumerable<ValidationError> errors, int statusCode = 400)
ApiException(System.Exception ex, int statusCode = 500)
ApiException(object custom, int statusCode = 400)

If you don’t like how the default properties are named, then you can now map whatever names you want for the property using the AutoWrapperPropertyMap attribute. For example, let's say you want to change the name of the default result property to something else like data, then you can simply define your own schema for mapping it like in the following:

public class MapResponseObject  
{
    [AutoWrapperPropertyMap(Prop.Result)]
    public object Data { get; set; }
}

You can then pass the MapResponseObject class to the AutoWrapper middleware like this:

app.UseApiResponseAndExceptionWrapper<MapResponseObject>();  

On successful requests, your response should now look something like this after mapping:

{
    "message": "Request successful.",
    "isError": false,
    "data": {
        "id": 7002,
        "firstName": "Vianne",
        "lastName": "Durano",
        "dateOfBirth": "2018-11-01T00:00:00"
    }
}

Notice that the default result attribute is now replaced with the data attribute.

Keep in mind that you are free to choose whatever property that you want to map. Here is the list of default properties that you can map:

[AutoWrapperPropertyMap(Prop.Version)]
[AutoWrapperPropertyMap(Prop.StatusCode)]
[AutoWrapperPropertyMap(Prop.Message)]
[AutoWrapperPropertyMap(Prop.IsError)]
[AutoWrapperPropertyMap(Prop.Result)]
[AutoWrapperPropertyMap(Prop.ResponseException)]
[AutoWrapperPropertyMap(Prop.ResponseException_ExceptionMessage)]
[AutoWrapperPropertyMap(Prop.ResponseException_Details)]
[AutoWrapperPropertyMap(Prop.ResponseException_ReferenceErrorCode)]
[AutoWrapperPropertyMap(Prop.ResponseException_ReferenceDocumentLink)]
[AutoWrapperPropertyMap(Prop.ResponseException_ValidationErrors)]
[AutoWrapperPropertyMap(Prop.ResponseException_ValidationErrors_Field)]
[AutoWrapperPropertyMap(Prop.ResponseException_ValidationErrors_Message)]

You can now define your own Error object and pass it to the ApiException() method. For example, if you have the following Error model with mapping configured:

public class MapResponseObject  
{
    [AutoWrapperPropertyMap(Prop.ResponseException)]
    public object Error { get; set; }
}

public class Error  
{
    public string Message { get; set; }

    public string Code { get; set; }
    public InnerError InnerError { get; set; }

    public Error(string message, string code, InnerError inner)
    {
        this.Message = message;
        this.Code = code;
        this.InnerError = inner;
    }

}

public class InnerError  
{
    public string RequestId { get; set; }
    public string Date { get; set; }

    public InnerError(string reqId, string reqDate)
    {
        this.RequestId = reqId;
        this.Date = reqDate;
    }
}

You can then throw an error like this:

throw new ApiException(  
      new Error("An error blah.", "InvalidRange",
      new InnerError("12345678", DateTime.Now.ToShortDateString())
));

The format of the output will now look like this:

{
    "isError": true,
    "error": {
        "message": "An error blah.",
        "code": "InvalidRange",
        "innerError": {
            "requestId": "12345678",
            "date": "10/16/2019"
        }
    }
}

If mapping wont work for you and you need to add additional attributes to the default API response schema, then you can now use your own custom schema/model to achieve that by setting the UseCustomSchema to true in AutoWrapperOptions as shown in the following code below:

app.UseApiResponseAndExceptionWrapper(new AutoWrapperOptions { UseCustomSchema = true }); 

Now let's say for example you wanted to have an attribute SentDate and Pagination object as part of your main API response, you might want to define your API response schema to something like this:

public class MyCustomApiResponse  
{
    public int Code { get; set; }
    public string Message { get; set; }
    public object Payload { get; set; }
    public DateTime SentDate { get; set; }
    public Pagination Pagination { get; set; }

    public MyCustomApiResponse(DateTime sentDate, object payload = null, string message = "", int statusCode = 200, Pagination pagination = null)
    {
        this.Code = statusCode;
        this.Message = message == string.Empty ? "Success" : message;
        this.Payload = payload;
        this.SentDate = sentDate;
        this.Pagination = pagination;
    }

    public MyCustomApiResponse(DateTime sentDate, object payload = null, Pagination pagination = null)
    {
        this.Code = 200;
        this.Message = "Success";
        this.Payload = payload;
        this.SentDate = sentDate;
        this.Pagination = pagination;
    }

    public MyCustomApiResponse(object payload)
    {
        this.Code = 200;
        this.Payload = payload;
    }

}

public class Pagination  
{
    public int TotalItemsCount { get; set; }
    public int PageSize { get; set; }
    public int CurrentPage { get; set; }
    public int TotalPages { get; set; }
}

To test the result, you can create a GET method to something like this:

public async Task<MyCustomApiResponse> Get()  
{
    var data = await _personManager.GetAllAsync();

    return new MyCustomApiResponse(DateTime.UtcNow, data,
        new Pagination
        {
            CurrentPage = 1,
            PageSize = 10,
            TotalItemsCount = 200,
            TotalPages = 20
        });
}

Running the code should give you now the following response format:

{
    "code": 200,
    "message": "Success",
    "payload": [
        {
            "id": 1,
            "firstName": "Vianne Maverich",
            "lastName": "Durano",
            "dateOfBirth": "2018-11-01T00:00:00"
        },
        {
            "id": 2,
            "firstName": "Vynn Markus",
            "lastName": "Durano",
            "dateOfBirth": "2018-11-01T00:00:00"
        },
        {
            "id": 3,
            "firstName": "Mitch",
            "lastName": "Durano",
            "dateOfBirth": "2018-11-01T00:00:00"
        }
    ],
    "sentDate": "2019-10-17T02:26:32.5242353Z",
    "pagination": {
        "totalItemsCount": 200,
        "pageSize": 10,
        "currentPage": 1,
        "totalPages": 20
    }
}

That’s it. One thing to note here is that once you use your own schema for your API response, you have the full ability to control how you would want to format your data, but at the same time losing some of the option configurations for the default API Response. The good thing is you can still take advantage of the ApiException() method to throw a user-defined error message.

The following properties are the options that you can set:

• ApiVersion
• ShowApiVersion
• ShowStatusCode
• IsDebug

• IsApiOnly
• WrapWhenApiPathStartsWith

• IgnoreNullValue
• UseCamelCaseNamingStrategy
• UseCustomSchema

• EnableResponseLogging
• EnableExceptionLogging

if you want to show the API version in the response, then you can do:

app.UseApiResponseAndExceptionWrapper(new AutoWrapperOptions { ShowApiVersion = true });

The default API version format is set to "1.0.0.0"

If you wish to specify a different version format, then you can do:

app.UseApiResponseAndExceptionWrapper(new AutoWrapperOptions { ShowApiVersion = true, ApiVersion = "2.0" });

if you want to show the StatusCode in the response, then you can do:

app.UseApiResponseAndExceptionWrapper(new AutoWrapperOptions { ShowStatusCode = true });

By default, AutoWrapper suppresses stack trace information. If you want to see the actual details of the error from the response during the development stage, then simply set the AutoWrapperOptions IsDebug to true:

app.UseApiResponseAndExceptionWrapper(new AutoWrapperOptions { IsDebug = true }); 

AutoWrapper is meant to be used for ASP.NET Core API project templates only. If you are combining API Controllers within your front-end projects like Angular, MVC, React, Blazor Server and other SPA frameworks that supports .NET Core, then use this property to enable it.

app.UseApiResponseAndExceptionWrapper(new AutoWrapperOptions { IsApiOnly = false} );

If you set the IsApiOnly option to false, you can also specify the segment of your API path for validation. By default it was set to "/api". If you want to set it to something else, then you can do:

app.UseApiResponseAndExceptionWrapper( new AutoWrapperOptions { 
          IsApiOnly = false, 
          WrapWhenApiPathStartsWith = "/myapi" 
});

This will activate the AutoWrapper to intercept HTTP responses when a request contains the WrapWhenApiPathStartsWith value.

Note that I would still recommend you to implement your API Controllers in a seperate project to value the separation of concerns and to avoid mixing route configurations for your SPAs and APIs.

You can now use the [AutoWrapIgnore] filter attribute for enpoints that you don't need to be wrapped.

For example:

[HttpGet]
[AutoWrapIgnore]
public async Task<IActionResult> Get()  
{
    var data = await _personManager.GetAllAsync();
    return Ok(data);
}

or

[HttpGet]
[AutoWrapIgnore]
public async Task<IEnumerable<Person>> Get()  
{
    return await _personManager.GetAllAsync();
}

Another good thing about AutoWrapper is that logging is already pre-configured. .NET Core apps has built-in logging mechanism by default, and any requests and responses that has been intercepted by the wrapper will be automatically logged (thanks to Dependency Injecton!). .NET Core supports a logging API that works with a variety of built-in and third-party logging providers. Depending on what supported .NET Core logging provider you use and how you configure the location to log the data (e.g text file, Cloud , etc. ), AutoWrapper will automatically write the logs there for you.

You can turn off Logging by setting EnableResponseLogging and EnableExceptionLogging options to false.

For example:

app.UseApiResponseAndExceptionWrapper(new AutoWrapperOptions {  
              EnableResponseLogging = false, 
              EnableExceptionLogging = false 
});

Swagger provides an advance documentation for your APIs where it allows developers to reference the details of your API endpoints and test them when necessary. This is very helpful especially when your API is public and you expect many developers to use it.

AutoWrapper omit any request with “/swagger” in the URL so you can still be able to navigate to the Swagger UI for your API documentation.

AutoWrapper version 2.x also now supports both .NET Core 2.1 and 2.2. You just need to install the Nuget package Newtonsoft.json first before AutoWrapper.Core.

• AutoWrapper: Prettify Your ASP.NET Core APIs with Meaningful Responses
• AutoWrapper: Customizing the Default Response Output

I’m pretty sure there are still lots of things to improve in this project, so feel free to try it out and let me know your thoughts. Comments and suggestions are welcome, please drop a message and I’d be happy to answer any queries as I can.

• Version 1.x.0 option additions and Version 2.x features were added based on the feedback from sondreb. Thank you!

• Vincent Maverick Durano - Blog

• 11/09/2019: AutoWrapper version 2.1.0 - added new options and features.
• 11/05/2019: AutoWrapper version 2.0.2 - added UnAuthorize and BadRequest method response.
• 10/17/2019: AutoWrapper version 2.0.1 - added new features.
• 10/06/2019: AutoWrapper version 1.2.0 - refactor, cleanup and bugfixes for SPA support.
• 10/04/2019: AutoWrapper version 1.1.0 - with newly added options.
• 09/23/2019: AutoWrapper version 1.0.0 - offcial release.
• 09/14/2019: AutoWrapper version 1.0.0-rc - prerelease.

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