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Check File Size before Uploading it in ASP.NET Core Uploader control

26 Oct 2021 / 1 minute to read

By using uploading event, you can get the file size before upload it to server. File object contains the file size in bytes only. You can convert the size to standard formats (KB or MB) using bytesToSize method.

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    var asyncSettings = new Syncfusion.EJ2.Inputs.UploaderAsyncSettings { SaveUrl = "", RemoveUrl = "" };

<div class="col-lg-8 control-section">
    <div class="control_wrapper">
        <ejs-uploader id="UploadFiles" asyncSettings="@asyncSettings" autoUpload="false" uploading="onBeforeUpload">

    function onBeforeUpload(args) {
        var uploadObj = document.getElementById("UploadFiles").ej2_instances[0];
        // get the file size in bytes
        var sizeInBytes = args.fileData.size;
        // get the file size in standard format
        alert("File size is: " + uploadObj.bytesToSize(sizeInBytes))
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;

namespace EJ2CoreSampleBrowser.Controllers.TextBoxes
    public partial class UploaderController : Controller
        public ActionResult DefaultFunctionalities()
            return View();
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.control_wrapper {
        max-width: 500px;
        margin: auto;

    .control_wrapper .e-upload .e-upload-drag-hover {
        margin: 0;

You can also explore ASP.NET Core File Upload feature tour page for its groundbreaking features. You can also explore our ASP.NET Core File Upload example to understand how to browse the files which you want to upload to the server.