How to keep the Text of a Read only TextBox after PostBack()?

Question

I have an ASP.NET TextBox and I want it to be ReadOnly. (The user modify it using another control)

But when there is a PostBack()

Answer 1

I've had this same issue but using Knockout binding 'enable' and ASP.Net Server Control Text.

This way:

<asp:TextBox ID="txtCity" runat="server" required="required" class="form-control" placeholder="City" data-bind="value: city, enable: !hasZipCode()"></asp:TextBox>

However, when the form was submitted this field value was always empty. This occurred, I presume, because if the control is disabled, it is not persist on the ViewState chain.

I solved replacing bindig 'enable' by 'attr{ readonly: hasZipCode}'

    <asp:TextBox ID="txtCity" runat="server" required="required" class="form-control" placeholder="City" data-bind="attr{ value: city, readonly: hasZipCode }">/asp:TextBox>