Blazor export to excel

Question

I am attempting to add an export to excel button on my blazor server side app. So far after combing the internet this is what I have done.

My button

    <div class="row text-right">
                <div class="col-12 p-3">
                    <button class="btn btn-outline-success" @onclick="@(() =>DownloadExcel(formValues.Region, formValues.startDate, formValues.endDate))">
                        Export to Excel&nbsp;
                        <i class="fa fa-file-excel" aria-hidden="true"></i>
                    </button>
               </div>
            </div>

My method in my .razor page

    public FileResult DownloadExcel(string Region, DateTime StartDate, DateTime EndDate)
    {
        FileResult ExcelFile = searchService.ExportToExcel(Region, StartDate, EndDate);
        return ExcelFile;
    }

And Finally my logic in my service

        public FileResult ExportToExcel(string Region, DateTime StartDate, DateTime EndDate)
        {
            var queryable = context.AuditCardPinrecords.Where(s => Region == s.RegionRecordId)
                .Where(s => s.AuditComplete == true)
                .Where(s => s.DateTime >= StartDate && s.DateTime <= EndDate).AsQueryable();

            var stream = new MemoryStream();

            using (var package = new ExcelPackage(stream))
            {
                var workSheet = package.Workbook.Worksheets.Add("Sheet1");
                workSheet.Cells.LoadFromCollection(queryable, true);
                package.Save();
            }


            string excelName = $"AuditPinRecords-{DateTime.Now.ToString("yyyyMMddHHmmssfff")}.xlsx";

            return File(stream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", excelName); 

        }

My expected result is to download the excel file. Unfortunately nothing happens on button click. Any advice would be greatly appreciated. Thanks!

Answer 1

The method shown below worked for both Blazor Server and WASM without JavaScript. I used Aspose.Cells, but it isn't dependent on any particular Excel Nuget package.

Controller:

[HttpGet("~/GetExcelReport")]
public IActionResult ExcelReport(string id)
{
        var license = new Aspose.Cells.License();
        license.SetLicense("Aspose.Total.NET.lic");

        var wb = new Workbook();
        var ws = wb.Worksheets[0];
        var cells = ws.Cells;
        ws.Name = "LW310";

        int rowNo = 0;
        
        cells[rowNo, 0].PutValue("Step");
        cells[rowNo, 1].PutValue("Prompt");
        cells[rowNo, 2].PutValue("Value");

        using (var ms = new MemoryStream())
        {
                wb.Save(ms, SaveFormat.Xlsx);
                ms.Position = 0;

                byte[] data = ms.ToArray();
                string fileName = "LW310_" + String.Format("{0:MM_dd_yyyy_hh_mm_ss_tt}", DateTime.Now) + ".xlsx";

                if (data != null)
                        return File(data, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", fileName);
                else
                        return new EmptyResult();
        }
}

Razor Page:

<button @onclick="ExportExcel">Export Excel</button>

@inject NavigationManager navMgr
async Task ExportExcel() => await Task.Run(() => navMgr.NavigateTo($"./getexcelreport?id={"testId"}", true));

Answer 2

I had a similar need and was able to piece together how to do it via javascript from this project: https://github.com/timplourde/dcidr-blazor

Static Utility Service:

public static class ExcelService
{
    public static byte[] GenerateExcelWorkbook()
    {
        var list = new List<UserInfo>()
        {
            new UserInfo { UserName = "catcher", Age = 18 },
            new UserInfo { UserName = "james", Age = 20 },
        };
        var stream = new MemoryStream();

        // ExcelPackage.LicenseContext = LicenseContext.NonCommercial;
        using (var package = new ExcelPackage(stream))
        {
            var workSheet = package.Workbook.Worksheets.Add("Sheet1");

            // simple way
            workSheet.Cells.LoadFromCollection(list, true);

            ////// mutual
            ////workSheet.Row(1).Height = 20;
            ////workSheet.Row(1).Style.HorizontalAlignment = ExcelHorizontalAlignment.Center;
            ////workSheet.Row(1).Style.Font.Bold = true;
            ////workSheet.Cells[1, 1].Value = "No";
            ////workSheet.Cells[1, 2].Value = "Name";
            ////workSheet.Cells[1, 3].Value = "Age";

            ////int recordIndex = 2;
            ////foreach (var item in list)
            ////{
            ////    workSheet.Cells[recordIndex, 1].Value = (recordIndex - 1).ToString();
            ////    workSheet.Cells[recordIndex, 2].Value = item.UserName;
            ////    workSheet.Cells[recordIndex, 3].Value = item.Age;
            ////    recordIndex++;
            ////}

            return package.GetAsByteArray();
        }
    }
}

public class UserInfo
{
    public string UserName { get; set; }
    public int Age { get; set; }
}

Create a js folder with a site.js file in the wwwroot folder

function saveAsFile(filename, bytesBase64) {
    var link = document.createElement('a');
    link.download = filename;
    link.href = "data:application/octet-stream;base64," + bytesBase64;
    document.body.appendChild(link); // Needed for Firefox
    link.click();
    document.body.removeChild(link);
}

In your _Host.cshtml file add the following script in the body section

<script src="~/js/site.js"></script>

In your .razor page that you want to export to excel from

@using YOUR_APP_NAME.Services

@inject IJSRuntime js

<Row Class="d-flex px-0 mx-0 mb-1">
    <Button Clicked="@DownloadExcelFile" class="p-0 ml-auto mr-2" style="background-color: transparent" title="Download">
        <span class="fa fa-file-excel fa-lg m-0" style="color: #008000; background-color: white;" aria-hidden="true"></span>
    </Button>
</Row>

@code {
    private void DownloadExcelFile()
    {
        var excelBytes = ExcelService.GenerateExcelWorkbook();
        js.InvokeVoidAsync("saveAsFile", $"test_{DateTime.Now.ToString("yyyyMMdd_HHmmss")}.xlsx", Convert.ToBase64String(excelBytes));
    }
}

Answer 3

A .razor component is not an HTTP endpoint like an MVC view is. Your return FileResult is not going to trigger a download by the browser.

You will need to create an MVC controller action and redirect the user there, or use JavaScript to invoke the a file save action. You would then need to use the JavaScript Interop to invoke the JS function.

window.msSaveBlob = function (payload, filename) {

    const createBlob = data => new Blob([data], { type: "text/csv;charset=utf-8;" });

    const buildDownloadLink = (blob, fileName) => {
        let link = document.createElement("a");
        link.setAttribute("href", URL.createObjectURL(blob));
        link.setAttribute("download", fileName);
        link.style = "visibility:hidden";
        return link;
    };
    const invokeDownload = link => {
        document.body.appendChild(link);
        link.click();
        document.body.removeChild(link);
    };
    const isHtmlDownloadAllowed = document.createElement("a").download !== undefined;
    const isSaveBlobAllowed = navigator.msSaveBlob;

    isSaveBlobAllowed ? navigator.msSaveBlob(createBlob(payload), filename) :
        isHtmlDownloadAllowed ? invokeDownload(buildDownloadLink(createBlob(payload), filename)) :
            console.log("Feature unsupported");

};

Of course there are also commercial libraries to help with these types of things. Telerik UI for Blazor Document Processing