c# - 如何确定视图中按钮的来源？

Question

页面上有一个按钮。
我在页面代码中没有看到这个按钮。
 
问题：如何确定视图中按钮的来源？
 
项目使用- ImportExportExcelASPNetCore //talkingdotnet //github.com  
启动应用程序后，会出现一个页面。
  页面代码中的哪里是Выберите файл按钮？

代码

@page
@model ImportExportExcelASPNetCore.Pages.ImportExportModel
@{
    ViewData["Title"] = "ImportExport";
}
<h2>Import Export using NPOI</h2>
<form method="post" enctype="multipart/form-data">
    <br/>
    <div class="row">
        <div class="col-md-4">
            <input type="file" id="fUpload" name="files" class="form-control" />
        </div>
        <div class="col-md-8">
            <input type="button" id="btnUpload" value="Upload" />
        </div>
    </div>
    <div class="row">
        <div class="col-md-8" style="padding-top:10px;">
            <button asp-page-handler="Export">Export</button>
        </div>
    </div>
    <br/>
    <div id="dvData"></div>
</form>
@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
    <script type="text/javascript" language="JavaScript">
        $(document).ready(function ()
        {
            $('#btnUpload').on('click', function ()
            {
                var fileExtension = ['xls', 'xlsx'];    //  Расширение файла
                var filename = $('#fUpload').val();     //  Имя файла
                if (filename.length == 0)
                {
                    alert("Please select a file.");
                    return false;
                }
                else
                {
                    var extension = filename.replace(/^.*\./, '');
                    if ($.inArray(extension, fileExtension) == -1)
                    {
                        alert("Please select only excel files.");
                        return false;
                    }
                }

                var fdata = new FormData();
                var fileUpload = $("#fUpload").get(0);
                var files = fileUpload.files;
                fdata.append(files[0].name, files[0]);

                $.ajax(
                    {
                    type: "POST",
                    url: "/ImportExport?handler=Import",
                        beforeSend: function (xhr)
                        {
                            xhr.setRequestHeader("XSRF-TOKEN",
                            $('input:hidden[name="__RequestVerificationToken"]').val());
                        },

                        data: fdata,
                    contentType: false,
                    processData: false,
                    success: function (response)
                    {
                        if (response.length == 0)
                            alert('Some error occured while uploading');
                        else
                        {
                            $('#dvData').html(response);
                        }
                    },
                        error: function (e)
                        {
                        $('#dvData').html(e.responseText);
                        }
                });
            })
        });
    </script>
}

标签： c#asp.netasp.net-core