Why failed with no error after concat two string?

I am using VB.NET
It was <asp:Label ID="Label4" runat="server" Text='<%#Eval("Advisor") %>'/>
if I changed it to:
<asp:Label ID="Label1" runat="server" Text='<%#String.Concat("Inputted By: ", Eval("Advisor"))%>'/>
building the page will fail but no error shows up

Even worse thing is: it still fails after I changed it back to original

What's wrong with this and how to find out the true fail reason? Thank you very much.
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