Migrating From 4.x

AjaxUploader 5.0 is designed to let older Web Forms projects move forward without forcing a full rewrite on day one.

What stays familiar

The CuteWebUI namespace still exists for upgrade scenarios.
Legacy controls such as Uploader, UploadAttachments, and UploadPersistedFile are still shipped.
Legacy event and file wrapper types such as UploaderEventArgs, AttachmentItem, and PersistedFile are still available.

What changed

The runtime is HTML5-based. Old Flash and Silverlight-era settings remain for compatibility, but they do not bring those runtimes back.
New development should prefer the AjaxUploader.* namespaces, especially AjaxFileUpload.
AjaxUploader.dll is the main shipping assembly for v5.
CuteWebUI.AjaxUploader.dll is only needed when an older project still references the old assembly name.
The v5 license file is ajaxuploader5.lic.
Local development on localhost, 127.0.0.1, or ::1 does not require license detection.

Recommended upgrade path

Replace the old binaries with the latest AjaxUploader.dll.
Keep your CuteWebUI markup and code-behind in place first.
Register the ajaxupload.axd handler and make sure uploads work end to end.
Verify your old server-side events and attachment flows on a real postback.
Migrate individual pages to AjaxUploader.Controls.* only when you want cleaner v5-native markup.

Practical assembly guidance

For a normal v5 Web Forms app:

Use AjaxUploader.dll
Register AjaxUploader.Controls

For an upgraded 4.x app that still has old assembly references:

Use AjaxUploader.dll
Optionally keep CuteWebUI.AjaxUploader.dll only if the application still depends on the old assembly identity

Typical upgrade pattern

Start by keeping the old control:

<%@ Register Assembly="AjaxUploader" Namespace="CuteWebUI" TagPrefix="CuteWebUI" %>

<CuteWebUI:Uploader ID="Uploader1" runat="server"
    InsertText="Select files"
    MultipleFilesUpload="true"
    OnFileUploaded="Uploader1_FileUploaded" />

Then move to the native v5 control later if you want:

<%@ Register Assembly="AjaxUploader" Namespace="AjaxUploader.Controls" TagPrefix="au" %>

<au:AjaxFileUpload ID="Uploader1" runat="server"
    ButtonText="Select files"
    Multiple="true"
    OnFileUploaded="Uploader1_FileUploaded" />

Compatibility expectation

The goal of the CuteWebUI layer is upgrade continuity:

old markup should keep compiling
old code-behind patterns should keep working
HTML5 upload behavior should be better than the old runtime

The goal is not to recreate the old browser plugins or every legacy visual behavior exactly.