Client-Side file size validation

Environment

Product

Telerik WebForms AsyncUpload for ASP.NET AJAX

Description

The aim of the article is to gain some kind of client side validation to restrict users from adding more than a pre-determined limit of files based upon total size of all uploaded files, not just each file or number of files.

Solution

This JavaScript code enforces client-side validation to prevent users from uploading more files than a preset limit based on the total size of all files uploaded, handling duplicate file detection and exceeding total size limits while providing real-time feedback during the upload process.

ASP.NET

<table>
    <tr>
        <td colspan="2">You may attach up to 20mb in files to the Email.</td>
    </tr>
    <tr>
        <td>Select File(s):</td>
        <td>
            <telerik:RadAsyncUpload ID="RadAsyncUpload1"
                OnClientFileSelected="OnFileSelected"
                OnClientFileUploadFailed="OnFileUploadFailed"
                OnClientFilesUploaded="OnFilesUploaded"
                OnClientProgressUpdating="OnProgressUpdating"
                OnClientFileUploaded="OnFileUploaded"
                OnClientFileUploadRemoved="OnFileUploadRemoved"
                runat="server">
            </telerik:RadAsyncUpload>
        </td>
    </tr>
</table>

JavaScript

var uploadsInProgress = 0;
var MAX_TOTAL_BYTES = 20971520;
var filesSize = new Array();
var OVERSIZE_MESSAGE = "You are only allowed to add up to 20mb of files total";
var isDuplicateFile = false;

function OnFileSelected(sender, args) {
    for (var fileindex in sender._uploadedFiles) {
        if (sender._uploadedFiles[fileindex].fileInfo.FileName == args.get_fileName()) {
            isDuplicateFile = true;
        }
    }

    if (!uploadsInProgress) {
        $("input[id$=btnSave]").attr("disabled", "disabled");
    }
    uploadsInProgress++;
}

function OnFilesUploaded(sender, args) {
    if (sender._uploadedFiles.length == 0) {
        filesSize = new Array();
        uploadsInProgress = 0;
        $("input[id$=btnSave]").removeAttr("disabled");
    }

    if (uploadsInProgress > 0) {
        DecrementUploadsInProgress();
    }
}

function OnProgressUpdating(sender, args) {
    filesSize[args.get_data().fileName] = args.get_data().fileSize;
}

function OnFileUploadFailed(sender, args) {
    DecrementUploadsInProgress();
}

function OnFileUploaded(sender, args) {
    DecrementUploadsInProgress();
    var totalBytes = 0;
    var numberOfFiles = sender._uploadedFiles.length;

    if (isDuplicateFile) {
        sender.deleteFileInputAt(numberOfFiles - 1);
        isDuplicateFile = false;
        sender.updateClientState();
        alert("You can't add the same file twice");
        return;
    }

    for (var index in filesSize) {
        totalBytes += filesSize[index];
    }

    if (totalBytes > MAX_TOTAL_BYTES) {
        sender.deleteFileInputAt(numberOfFiles - 1);
        sender.updateClientState();
        alert(OVERSIZE_MESSAGE);
    }
}

function OnFileUploadRemoved(sender, args) {
    if (args.get_fileName() != null) {
        if (!isDuplicateFile) {
            delete filesSize[args.get_fileName()];
        }
    }
}

function DecrementUploadsInProgress() {
    uploadsInProgress--;
    if (!uploadsInProgress) {
        $("input[id$=btnSave]").removeAttr("disabled");
    }
}