您尝试打开的文件的格式与 Asp.Net 中文件扩展名指定的格式不同

您尝试打开的文件的格式与文件扩展名指定的格式不同，尝试在 Excel 中打开文件时出现 C# 错误。

这是我的代码

public ActionResult Export(string filterBy)
{
    MemoryStream output = new MemoryStream();
    StreamWriter writer = new StreamWriter(output, Encoding.UTF8);

    var data = City.GetAll().Select(o => new
    {
        CountryName = o.CountryName,
        StateName = o.StateName,
        o.City.Name,
        Title = o.City.STDCode
    }).ToList();
    var grid = new GridView { DataSource = data };
    grid.DataBind();
    var htw = new HtmlTextWriter(writer);

    grid.RenderControl(htw);

    writer.Flush();
    output.Position = 0;

    return File(output, "application/vnd.ms-excel", "test.xls");

}

当我尝试打开 Excel 时出现此错误

您尝试打开的文件的格式与 由文件扩展名指定

单击“是”后，文件可以正确打开。但我不希望出现此消息。

我用过CloseXML http://closedxml.codeplex.com/来解决问题。

public static void ExportToExcel(IEnumerable<dynamic> data, string sheetName)
{
    XLWorkbook wb = new XLWorkbook();
    var ws = wb.Worksheets.Add(sheetName);
    ws.Cell(2, 1).InsertTable(data);
    HttpContext.Current.Response.Clear();
    HttpContext.Current.Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
    HttpContext.Current.Response.AddHeader("content-disposition", String.Format(@"attachment;filename={0}.xlsx",sheetName.Replace(" ","_")));

    using (MemoryStream memoryStream = new MemoryStream())
    {
        wb.SaveAs(memoryStream);
        memoryStream.WriteTo(HttpContext.Current.Response.OutputStream);
        memoryStream.Close();
    }

    HttpContext.Current.Response.End();
}

使用在我的项目中安装 ClosedXMLNuget 包管理器 https://www.nuget.org/packages/ClosedXML/.