将blob转换为Excel文件并下载，文件无法打开

Question

I have an api which return below response, which contain the excel file content.

So now I need to convert them into excel file and download for the user.

Here is the api function

   [HttpGet]
    [IgnoreAntiforgeryToken]
    public async Task<IActionResult> DownloadLoadedTrnFile(string S3Path)
    {
        try
        {
            string bucket = "taurus-" + GetEnvironmentSettings() + "-trn";
            string fileName = "";
            string[] fileStr = S3Path.Split('-');
            if (fileStr.Count() > 0)
            {
                fileName = fileStr.Last();
            }
            Stream responseStream = await _imageStore.GetImage(bucket, S3Path);
            if (responseStream == null)
                return NotFound();
            using (MemoryStream ms = new MemoryStream())
            {
                responseStream.CopyTo(ms);

                var finalResult = File(System.Text.UTF8Encoding.UTF8.GetString(ms.ToArray()), MimeTypesMap.GetMimeType(S3Path), fileName);
                return Ok(finalResult);
            }
        }
        catch (Exception ex)
        {
            return StatusCode(500, "Error in downloading file.");
        }
    }





     public async Task<Stream> GetImage(string bucketName, string objectKey)
    {
        GetObjectRequest originalRequest = new GetObjectRequest
        {
            BucketName = bucketName,
            Key = objectKey
        };
    
        try
        {
            GetObjectResponse response = await S3Client.GetObjectAsync(originalRequest);

            // AWS HashStream doesn't support seeking so we need to copy it back to a MemoryStream
            MemoryStream outputStream = new MemoryStream();
            response.ResponseStream.CopyTo(outputStream);

            outputStream.Position = 0;

            return outputStream;
        }
        catch (AmazonS3Exception ex)
        {
            // Not found if we get an exception
            return null;
        }
    }

I have such function in the front-end as below,

      function saveTextAsFile(data, filename, contentType) {
        if (!data) {
            console.error('Console.save: No data')
            toastr.error("No data received from server");
            return;
        }

        if (!filename) filename = 'noname.xlsx';

        var blob = new Blob([s2ab(atob(data))], {
            type: contentType
        });


        var a = document.createElement("a");
        a.href = URL.createObjectURL(blob);
        a.download = filename;
        a.click();
    }

and function

     function s2ab(s) {
        var buf = new ArrayBuffer(s.length);
        var view = new Uint8Array(buf);
        for (var i = 0; i != s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
        return buf;
    }

This function is working fine with excel that only has normal text. However, this excel i am trying to download, it has rich content such as color border, dropdown, multiple sheets.

When I try to use this same function to download the excel file, it throw me this error:

To help you more understand my problem, here is t he API HTTP CAll

I have try to search solution online but there is no luck. I actually do not understand what is the problem here. Anything will help thanks.

Answer 1

Thanks for all the replies and make my head around a little bit finally I fixed this issue.

Well, found the problem with it is because in the API I wrap that inside UTF-8. however, it (Excel) shouldn't be wrapped in UTF-8. only If I was downloading a csv file.

   var finalResult = File(System.Text.UTF8Encoding.UTF8.GetString(ms.ToArray()), 
   MimeTypesMap.GetMimeType(S3Path), fileName);

Changed to

   var finalResult = File(ms.ToArray(), MimeTypesMap.GetMimeType(S3Path), fileName);