How do I set a maximum file size on the ajaxuploader?

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VB

Ajax

upload

How do I set a maximum file size on the AjaxUploader? I use asp.net/vb.net. I've tried some examples I've seen online which edit the webconfig file but still it doesn't work. I feel it should be as simple as below..

<ajaxToolkit:AjaxFileUpload ID="AjaxFileUpload1" runat="server"
                            onclientuploadcompleteall="onClientUploadCompleteAll" AllowedFileTypes="mov,mp4,mpeg,avi,m4v" maxfilesize ="7000" />

What I have tried:

I Tried doing maxfilesize ="7000" as below but it doesn't work.