Question about the "runat" attribute in ASP.NET?

Question

I went through this thread but couldn't understand much. I am very new to ASP/HTML/Server-side programming.

I tried running this code on a .aspx file:

<form id="form1" action="Default.aspx">
    <div>
        <asp:Label ID="lblName"></asp:Label>

    </div>
</form>

And I got an error when I tried to use this in the CodeFile:

protected void Page_Load(object sender, EventArgs e)
    {
        lblName.Text = "123";
    }

"lblName does not exist".

But if I use runat="server" attribute with the label, then this code works.

Also, is there any concept of nesting the runat attribute. e.g, If I specify runat=server for the form above, will all my controls inside the form automatically be configured to run at server? How does this attribute work?

In which case would I be required to specify runat=server for the and for the tag? How does the server-side know that the label is inside the form if I don't have a form object at server side? Or am I missing something?

ars ars · Accepted Answer · 2010-07-18T08:16:54

Any element marked with runat="server" lets the framework know that this will be a control on the server side. This article has more details:

Exploring the Runat Attribute

Question about the "runat" attribute in ASP.NET?

2 Answers