Hi @peter liles ,
First, you need to pass the value to confirm whether the MessageID has a value.
I suggest that you can use Request.QueryString to accept a collection of URL query strings.
PostBackUrl='<%# String.Format("~/MyProject/AdminManager - Copy/Messaging/Pictures.aspx ?id={0}", Request.QueryString["MessageID"]) %>'
Best regards,
Lan Huang
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