I'm sure this is simple, I need to disable a button on my html page if a variable doesn't have a value from inside the code.

```
        <asp:Linkbutton ID="eastMinute" runat="server" CssClass="btn btn-default" Text="Open Once" Width="95%" />

```

I've found several options for disabling the button if there is no text for form validation but I haven't found a way to actually connect the VB code with my ASPX page... 

My thought was:

```
    'Logic for button enable
    If (username.Length < 0) Then eastOpen_Click.Enabled = False
    Else eastOpen_Click.Enabled = True

```

But with that I get an argument not specified error.