Instantiating an Iformfile from a Physical File

How to instantiate an instance of FormFile in C# without Moq?

Thanks to Hans his comment, the actual answer is:

using (var stream = File.OpenRead("placeholder.pdf"))
{
    var file = new FormFile(stream, 0, stream.Length, null, Path.GetFileName(stream.Name))
    {
        Headers = new HeaderDictionary(),
        ContentType = "application/pdf"
    };
}

How to mock an IFormFile for a unit/integration test in ASP.NET Core?

Assuming you have a Controller like..

public class MyController : Controller {
    public Task<IActionResult> UploadSingle(IFormFile file) {...}
}

...where the IFormFile.OpenReadStream() is accessed with the method under test.

As of ASP.NET Core 3.0, use an instance of the FormFile Class which is now the default implementation of IFormFile.

Here is an example of the same test above using FormFile class

[TestClass]
public class IFormFileUnitTests {
    [TestMethod]
    public async Task Should_Upload_Single_File() {
        //Arrange
       
        //Setup mock file using a memory stream
        var content = "Hello World from a Fake File";
        var fileName = "test.pdf";
        var stream = new MemoryStream();
        var writer = new StreamWriter(stream);
        writer.Write(content);
        writer.Flush();
        stream.Position = 0;

        //create FormFile with desired data
        IFormFile file = new FormFile(stream, 0, stream.Length, "id_from_form", fileName);
        
        MyController sut = new MyController();
        
        //Act
        var result = await sut.UploadSingle(file);

        //Assert
        Assert.IsInstanceOfType(result, typeof(IActionResult));
    }
}

Before the introduction of the FormFile Class or in in cases where an instance is not needed you can create a test using Moq mocking framework to simulate the stream data.

[TestClass]
public class IFormFileUnitTests {
    [TestMethod]
    public async Task Should_Upload_Single_File() {
        //Arrange
        var fileMock = new Mock<IFormFile>();
        //Setup mock file using a memory stream
        var content = "Hello World from a Fake File";
        var fileName = "test.pdf";
        var ms = new MemoryStream();
        var writer = new StreamWriter(ms);
        writer.Write(content);
        writer.Flush();
        ms.Position = 0;
        fileMock.Setup(_ => _.OpenReadStream()).Returns(ms);
        fileMock.Setup(_ => _.FileName).Returns(fileName);
        fileMock.Setup(_ => _.Length).Returns(ms.Length);

        var sut = new MyController();
        var file = fileMock.Object;

        //Act
        var result = await sut.UploadSingle(file);

        //Assert
        Assert.IsInstanceOfType(result, typeof(IActionResult));
    }
}

Good way to get images from the file system and send them using HttpClient to an API in C#

IFormFile represents a file sent with the HttpRequest. That is, it is used on the server receiving the files. In your case, you should use MultipartFormDataContent and ByteArrayContent.

        var file = await File.ReadAllBytesAsync("your path");

        HttpClient httpClient = new HttpClient();
        MultipartFormDataContent form = new MultipartFormDataContent();

        form.Add(new ByteArrayContent(file, 0, file.Length), "Image1", "image1.jpg");
        HttpResponseMessage response = await httpClient.PostAsync("your url", form);

This way, Image1 can be used as IFormFile on your server.

C# IFormFile as ZipFile

IFormFile is just a wrapper for the received file. You should still read the actual file do something about it. For example, you could read the file stream into a byte array and pass that to the service:

byte[] fileData;
using (var stream = new MemoryStream((int)file.Length))
{
    file.CopyTo(stream);
    fileData = stream.ToArray();
}

Or you could copy the stream into a physical file in the file system instead.

But it basically depends on what you actually want to do with the uploaded file, so you should start from that direction and the convert the IFormFile into the thing you need.

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If you want to open the file as a ZIP and extract something from it, you could try the ZipArchive constructor that takes a stream. Something like this:

using (var stream = file.OpenReadStream())
using (var archive = new ZipArchive(stream))
{
    var innerFile = archive.GetEntry("foo.txt");
    // do something with the inner file
}

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