Excel Exporter - IAsyncDisposable

Hi,

Thank you for your patience. I reviewed your project and found that the issue is not directly related to the fact that IXlExporter doesn't implement the IAsyncDisposable interface. The issue occurs because you pass the Response.Body property of the HttpResponseStream type to the CreateExcelFileAsync method. This results in an error because the HttpResponseStream doesn't support the Write method and requires the WriteAsync method.

The Excel Export Library is not thread-safe; thus, I recommend that you modify the CreateExcelFileAsync method as follows:

C#
public static async Task CreateExcelFileAsync(XlDocumentFormat format, Stream stream) {
    await Task.Run(() => {
        var variables = GetValues();
        IXlExporter exporter = XlExport.CreateExporter(format);
        using (IXlDocument document = exporter.CreateDocument(stream)) {
            using (var sheet = document.CreateSheet()) {
                sheet.Name = "Sheet 1";
                using (var column = sheet.CreateColumn()) {
                }
                using (var row = sheet.CreateRow()) {
                    foreach (var value in variables) {
                        using (var cell = row.CreateCell()) {
                            cell.Value = value;
                        }
                    }
                }
            }
        }
    });
}
public static IEnumerable<int> GetValues() {
    for (int indexer = 0; indexer < 10; indexer++) {
        yield return indexer;
    }
}

Then, you can modify the GetExcel method in the following manner:

C#
//solution 1
[HttpGet("getExcelOne")]
public async Task<IActionResult> GetExcelOne() {
    using MemoryStream ms = new MemoryStream();
    await CreateExcelFileAsync(XlDocumentFormat.Xlsx, ms);
    return File(ms.ToArray(), "application/octet-stream", fileName);
}

//solution 2
[HttpGet("getExcelTwo")]
public async Task GetExcelTwo() {
    using MemoryStream ms = new MemoryStream();
    await CreateExcelFileAsync(XlDocumentFormat.Xlsx, ms);
    Response.Clear();
    Response.Headers.Append("Content-Disposition", "attachment; filename=" + fileName);
    Response.Headers.Append("Content-Length", ms.Length.ToString());
    Response.ContentType = "application/octet-stream";
    await Response.Body.WriteAsync(ms.ToArray(), 0, (int)ms.Length);
    await Console.Out.WriteLineAsync("This won't be hit");
}

Attached is the updated project. Please review it and let me know if this solution is suitable.