How to check file size before upload in ASP.NET MVC File Upload

26 Aug 20261 minute to read

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

CSHTML

@using Syncfusion.EJ2

<div class="col-lg-8 control-section">
    <div class="control_wrapper">
        @Html.EJS().Uploader("UploadFiles").Uploading("onBeforeUpload").AutoUpload(false).AsyncSettings(new Syncfusion.EJ2.Inputs.UploaderAsyncSettings { SaveUrl = "https://services.syncfusion.com/aspnet/production/api/FileUploader/Save", RemoveUrl = "https://services.syncfusion.com/aspnet/production/api/FileUploader/Remove" }).Render()
    </div>
</div>

<script>

    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))
    }

</script>

Index.css

.control_wrapper {
        max-width: 500px;
        margin: auto;
    }

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

Explore the ASP.NET MVC File Upload feature tour page to discover its groundbreaking features. You can also check out our ASP.NET MVC File Upload example to see how to browse and select files for upload to the server.