After the Asp.net Textbox Control is set to readonly, it cannot be returned.

It is strange that such a strange problem has never been encountered before. It can be normal on other machines and may be related to the ASP. NET version.
I use ASP. NET 2.0. When it is changed to ASP. NET 1.0, it will be normal. The Textbox Control readonly = true can be returned.
In ASP. NET 1.0, readonly = true will be returned.
In ASP. NET 2.0, if readonly = true, it will not be returned.

Solution:
<Asp: textbox id = "username" runat = "server" readonly = "true"> </ASP: textbox>
Remove readonly = "true" and change it
<Asp: textbox id = "username" runat = "server"> </ASP: textbox>

In the backgroundCodeTo control read-only attributes.
Username. Attributes. Add ("readonly", "true ");
In this way, the Textbox Control read-only in ASP. NET 2.0 can also be returned.