How to allow a file download?

[hputus]

Several of my API methods result in a file download. How can I get Swashbuckle to download a file through the UI for these methods?

I've added an IOperationFilter with the following Apply method to add a "produces" attribute to certain methods:

public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
{
    if (apiDescription.ID == "GETapi/Templates/{id}")
    {
        operation.produces.Add("application/octet-stream");
    }
}

But when I execute this method through the Swashbuckle UI it displays the file contents in the "Response Body" textarea. Is there a way of getting a file to actually download?

Thanks

[domaindrivendev]

This is more of a swagger-ui issue. In fact, a quick search brought me to the following issue

swagger-api/swagger-ui#1196

Looks like the fix has gone in and so should be available with the next SB release.

[centur]

Hi. I'm trying to do the similar thing - generate correct swagger description for file download endpoints.
As per swagger spec - to show that the response is file - it must have special "type": "file" and correct 'produces' mime-type. I can set correct mime-type but can't find any way to force response schema type to be 'file'. looked through the Swashbuckle code and it seems that there is nothing that allow you to set type for schema on per operation\action basis.

[domaindrivendev]

@centur - you can wire up an IOperationFilter (see readme for details). It would look something like this ...

public class UpdateFileDownloadOperations : IOperationFilter
{
    public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
    {
        if (operation.operationId == "FileDownload_GetFile")
        {
            operation.produces = new[] { "application/octet-stream" };
            operation.responses["200"].schema = new Schema { type = "file" };
        }
    }
}

I've used this to create a valid spec, but it seems the UI still doesn't support the downloads yet ...

[centur]

Thanks a lot.

[lakeba]

@domaindrivendev Please inform about the format returned in the API method attribute

[domaindrivendev]

@lakeba - you'll have to elaborate your question, I really have no idea what you're asking?

[OzBob]

Here's one, I rolled my own based on @domaindrivendev code. I have another IOperationFilter extension for setting the ResponseType

Controller:

[SwaggerFileResponse(HttpStatusCode.OK, "File Response")]
public HttpResponseMessage GetFile(string id)...

Attribute:

/// <summary>
/// SwaggerFileResponseAttribute
/// </summary>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false)]
public sealed class SwaggerFileResponseAttribute : SwaggerResponseAttribute
{
    public SwaggerFileResponseAttribute(HttpStatusCode statusCode) : base(statusCode)
    {
    }

    public SwaggerFileResponseAttribute(HttpStatusCode statusCode, string description = null, Type type = null)
        : base(statusCode, description, type)
    {
    }
    public SwaggerFileResponseAttribute(int statusCode) : base(statusCode)
    {
    }

    public SwaggerFileResponseAttribute(int statusCode, string description = null, Type type = null)
        : base(statusCode, description, type)
    {
    }
}

Extension:

public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
    {
        if (apiDescription.GetControllerAndActionAttributes<SwaggerResponseRemoveDefaultsAttribute>().Any())
            operation.responses.Clear();

        var responseAttributes = apiDescription.GetControllerAndActionAttributes<SwaggerFileResponseAttribute>()
            .OrderBy(attr => attr.StatusCode);

        foreach (var attr in responseAttributes)
        {
            var statusCode = attr.StatusCode.ToString();

            Schema responseSchema = new Schema { format = "byte", type = "file" };

            operation.responses[statusCode] = new Response
            {
                description = attr.Description ?? InferDescriptionFrom(statusCode),
                schema = responseSchema
            };
        }
    }

    private string InferDescriptionFrom(string statusCode)
    {
        HttpStatusCode enumValue;
        if (Enum.TryParse(statusCode, true, out enumValue))
        {
            return enumValue.ToString();
        }
        return null;
    }

SwaggerConfig

GlobalConfiguration.Configuration.EnableSwagger(c => 
    c.OperationFilter<UpdateFileResponseTypeFilter>();
);

[MrLinDowsMac]

@OzBob Your code generates what I need. Except for one line:

_httpResponse = await this.Client.HttpClient.SendAsync(_httpRequest, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);

That is inside in a method of the generated code that I use to call the my service, but I can't get my file. I just found that only works with:
_httpResponse = await this.Client.HttpClient.SendAsync(_httpRequest, cancellationToken).ConfigureAwait(false);

Is there a way to generate it like that? In an earlier attempt it generates like that when HttpOperationResponse< object >() instead HttpOperationResponse<System.IO.Stream>()

[OzBob]

@MrLinDowsMac Do you mean 'generates' by using AutoRest on the swagger file to generate a client? There may be more swagger instructions required to get the output you need. If you manually play with the swagger file until that works then we can update the sample Filter above ...

[MrLinDowsMac]

@OzBob Yes, I mean that your code generates the json metadata file that autorest generates as c# files, with the only problem that I described. I have no clue which changes I have to do in the custom filters to avoid autorest generate file with that line like that. That httpCompletitionOption is messing it up. It works only with ResponseContentRead.

[OzBob]

@MrLinDowsMac

Generated with:
AutoRest\0.17\AutoRest.exe" -codeGenerator CSharp -input ..\swagger.json -OutputDirectory Client -namespace MyApi -AddCredentials true -Header NONE -ClientName MyClient

This is the Client Code I use when processing the SendAsync:

`

//lots deleted ...
_httpResponse = await base.HttpClient.SendAsync(_httpRequest, cancellationToken).ConfigureAwait(false);

if (_shouldTrace)
{
	ServiceClientTracing.ReceiveResponse(_invocationId, _httpResponse);
}
HttpStatusCode _statusCode = _httpResponse.StatusCode;
cancellationToken.ThrowIfCancellationRequested();
if ((int)_statusCode != 200)
{
	var ex = new HttpOperationException(string.Format("Operation returned an invalid status code '{0}'", _statusCode));
	ex.Request = new HttpRequestMessageWrapper(_httpRequest, _requestContent);
	ex.Response = new HttpResponseMessageWrapper(_httpResponse, "{\"status\":" + _statusCode + ", \"error\":\"unkown\"  }");
	if (_shouldTrace)
	{
		ServiceClientTracing.Error(_invocationId, ex);
	}
	_httpRequest.Dispose();
	if (_httpResponse != null)
	{
		_httpResponse.Dispose();
	}
	throw ex;
}
// Create Result
var _result = new HttpOperationResponse<byte[]>();
_result.Request = _httpRequest;
_result.Response = _httpResponse;
// Deserialize Response
if ((int)_statusCode == 200)
{
	try
	{
		_result.Body = await _httpResponse.Content.ReadAsByteArrayAsync().ConfigureAwait(false);
	}
	catch (Exception ex)
	{
		if (_shouldTrace)
		{
			ServiceClientTracing.Error(_invocationId, ex);
		}
		_httpRequest.Dispose();
		if (_httpResponse != null)
		{
			_httpResponse.Dispose();
		}
		throw ex;
	}
}
//more code ....

`

[MrLinDowsMac]

Mmmm... I don't know why is generating you a ReadAsByteArrayAsync, I get a ReadAsStreamAsync instead. I used something like this:

C:\_Sources\MyAPIproject\packages\AutoRest.0.17.3\tools>AutoRest.exe -Input http:/
/localhost:52977/swagger/docs/v1 -Output ..\clientproject -AddCredentials false -Namespace MyAPIproject.Pdfservice -codeGenerator CSharp

which generates this:

//omitted code...
// This line is messing up my requests:
            _httpResponse = await this.Client.HttpClient.SendAsync(_httpRequest, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);
            if (_shouldTrace)
            {
                Microsoft.Rest.ServiceClientTracing.ReceiveResponse(_invocationId, _httpResponse);
            }
            System.Net.HttpStatusCode _statusCode = _httpResponse.StatusCode;
            cancellationToken.ThrowIfCancellationRequested();
            string _responseContent = null;
            if ((int)_statusCode != 200)
            {
                var ex = new Microsoft.Rest.HttpOperationException(string.Format("Operation returned an invalid status code '{0}'", _statusCode));
                if (_httpResponse.Content != null) {
                    _responseContent = await _httpResponse.Content.ReadAsStringAsync().ConfigureAwait(false);
                }
                else {
                    _responseContent = string.Empty;
                }
                ex.Request = new Microsoft.Rest.HttpRequestMessageWrapper(_httpRequest, _requestContent);
                ex.Response = new Microsoft.Rest.HttpResponseMessageWrapper(_httpResponse, _responseContent);
                if (_shouldTrace)
                {
                    Microsoft.Rest.ServiceClientTracing.Error(_invocationId, ex);
                }
                _httpRequest.Dispose();
                if (_httpResponse != null)
                {
                    _httpResponse.Dispose();
                }
                throw ex;
            }
            // Create Result
            var _result = new Microsoft.Rest.HttpOperationResponse<System.IO.Stream>();
            _result.Request = _httpRequest;
            _result.Response = _httpResponse;
            // Deserialize Response
            if ((int)_statusCode == 200)
            { //**  ---------------- HERE ------------------    **
                _result.Body = await _httpResponse.Content.ReadAsStreamAsync().ConfigureAwait(false);
            }
            if (_shouldTrace)
            {
                Microsoft.Rest.ServiceClientTracing.Exit(_invocationId, _result);
            }
            return _result;
        }
//more code