Question

In the ASP.net, I try to set a variable value to hidden field, but I get exception.

In the first output, it is correct. then I put it into hidden field, failed.

How to fix it ?

 user name: <%= User.Identity.Name %> // output is correct
    <form runat=Server>
    <asp:HiddenField id="HiddenField1" value=<%= User.Identity.Name %> runat=Server />
    </form>

error

Parser Error 
Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. 

Parser Error Message: Server tags cannot contain <% ... %> constructs.

Answer 1

Give quote around your scriplet like given below.

 value='<%= User.Identity.Name %>'

Change

 <asp:HiddenField id="HiddenField1" value=<%= User.Identity.Name %> runat=Server />

To

 <asp:HiddenField id="HiddenField1" value='<%= User.Identity.Name %>' runat=Server />