.NET Core Razor Pages+ClosedXML+Unobtrusive AJAX 文件下载失败

你用了AJAX提交表单，但浏览器不会自动处理AJAX请求返回的文件流响应，所以代码执行无报错但没有下载动作。AJAX默认用于获取JSON/文本数据，无法直接触发文件下载。

方案1：改用普通表单提交（最简单） #

直接移除form标签里的data-ajax相关属性，让表单以普通方式提交，浏览器会自动处理后端返回的文件流：

<form class="d-flex flex-row" method="post" asp-page-handler="ExportToExcel">            
    <button type="submit" class="btn btn-primary" data-bs-toggle="tooltip" data-bs-placement="top" title="Export to Excel"><i class="fa-light fa-cloud-arrow-down"></i></button>
</form>

后端代码无需修改，保持原样即可。

方案2：保留AJAX，前端手动触发下载（适合需要页面不刷新的场景） #

如果必须用AJAX，需要后端返回文件的Base64编码，再由前端处理并触发下载：

后端修改（返回Base64数据） #

public IActionResult OnPostExportToExcel()
{
    AssetsList = _context.Assets.ToList();

    using (var workbook = new XLWorkbook())
    {
        var worksheet = workbook.Worksheets.Add("Assets");
        var currentRow = 1;
        worksheet.Cell(currentRow, 1).Value = "AssetName";
        // 填充其他列逻辑...

        foreach (Asset asset in AssetsList)
        {
            currentRow++;
            worksheet.Cell(currentRow, 1).Value = asset.AssetName ?? "";
            // 填充其他列逻辑...
        }

        var fileName = "AssetsExport-" + DateTime.Now.ToString("yyyyMMdd-HHmmssfff") + ".xlsx";

        using (var stream = new MemoryStream())
        {
            workbook.SaveAs(stream);
            stream.Position = 0;
            byte[] fileBytes = stream.ToArray();
            string base64 = Convert.ToBase64String(fileBytes);
            
            return Json(new { 
                fileName = fileName, 
                fileBase64 = base64,
                contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
            });
        }
    }
}

前端修改（处理Base64并触发下载） #

<form class="d-flex flex-row" method="post" asp-page-handler="ExportToExcel" data-ajax="true" data-ajax-method="post" data-ajax-success="handleDownload" data-ajax-failure="ajaxValidationHandler">            
    <button type="submit" class="btn btn-primary" data-bs-toggle="tooltip" data-bs-placement="top" title="Export to Excel"><i class="fa-light fa-cloud-arrow-down"></i></button>
</form>

<script>
function handleDownload(response) {
    const byteCharacters = atob(response.fileBase64);
    const byteNumbers = new Array(byteCharacters.length);
    for (let i = 0; i < byteCharacters.length; i++) {
        byteNumbers[i] = byteCharacters.charCodeAt(i);
    }
    const byteArray = new Uint8Array(byteNumbers);
    const blob = new Blob([byteArray], { type: response.contentType });
    
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = response.fileName;
    document.body.appendChild(a);
    a.click();
    URL.revokeObjectURL(url);
    document.body.removeChild(a);
}
</script>

内容的提问来源于stack exchange，提问作者s15199d