Download a file using IDownstreamApi in Microsoft.Identity.Web

Question

I'm trying to download a file using IDownstreamApi I've tried the following code

    var file = await downstreamApi.GetForAppAsync<Stream>(Definitions.FileshareApi, options =>
    {
        options.RelativePath = $"{ApiPaths.FileDownload}{sourceUri}";
    }, cancellationToken: cancellationToken);
    if(file != null)
    {
        var target = new FileStream(targetFilePath, FileMode.Create);
        file.CopyTo(target);
        return true;
    }

but I get the following exception

System.Text.Json.JsonException: 'The JSON value could not be converted to System.IO.Stream. Path: $ | LineNumber: 0 |

Is it possible to download a file using the IDownstreamApi. If how do you use it to do this.

score 0 · Answer 1 · answered Jul 19 '23 at 06:48

0

This method is deserializing received JSON data into this type. downstreamApi.GetForAppAsync<SomeType>(...) will just:

Using GET method receive data from url
Treat it as JSON content
Try to deserialize this content into SomeType

So basically your code is trying to deserialize it to Stream object, which is not the same as putting content into stream.

answered Jul 19 '23 at 06:48

GroM

1

I already understood that, what I'm trying to figure out is if it's possible to use the downstreamApi to download the file or if it's designed to only deserialize the response into a strongly typed object – Mark Jul 19 '23 at 09:22

score 0 · Accepted Answer · answered Jul 19 '23 at 09:59

Figured it out myself:

    var response = await downstreamApi.CallApiForAppAsync(Definitions.FileshareApi, options =>
    {
        options.HttpMethod = HttpMethod.Get;
        options.RelativePath = $"{ApiPaths.FileDownload}{sourceUri}";
    }, cancellationToken: cancellationToken);
    if (response != null)
    {
        using Stream output = File.OpenWrite(Path.Combine(targetFilePath, targetFileName));
        response.Content.CopyTo(output, null, cancellationToken);
    }

Download a file using IDownstreamApi in Microsoft.Identity.Web

2 Answers2