How to delete file after download with ASP.NET MVC?

You can return just regular FileStreamResult which is opened with FileOptions.DeleteOnClose. File stream will be disposed with result by asp.net. This answer dosen't require usage of low level response methods which may backfire in certain situations. Also no extra work will be done like loading file to memory as whole.

var fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.None, 4096, FileOptions.DeleteOnClose);
return File(
    fileStream: fs,
    contentType: System.Net.Mime.MediaTypeNames.Application.Octet,
    fileDownloadName: "File.abc");

This answer is based on answer by Alan West and comment by Thariq Nugrohotomo.

Read in the bytes of the file, delete it, call the base controller's File action.

public class MyBaseController : Controller
{
    protected FileContentResult TemporaryFile(string fileName, string contentType, string fileDownloadName)
    {
        var bytes = System.IO.File.ReadAllBytes(fileName);
        System.IO.File.Delete(fileName);
        return File(bytes, contentType, fileDownloadName);
    }
}

BTW, you may refrain from this method if you're dealing with very large files, and you're concerned about the memory consumption.