ViewState doesn't work on post back ASP.NET C#

Question

I am attempting to create a simple "recover" button for a field of values. For some reason, strings stored in ViewState do not show. I followed a tutorial so I really don't know what I did wrong, I also searched the web for an answer, the main issue for many being that they didn't have ViewState enabled in the page, which I didn't also so I added it (but the button still doesn't work). As for the way I wrote the code, or how I use ViewState, I was unable to find an issue. Any help would be appreciated.

So this is what I have in the Contact.aspx page:

<%@ Page Title="" Language="C#" EnableViewState="true"/*...*/

<asp:TextBox class="form-control" id="usr" runat="server"/>

<asp:Button Text="Send" ID="buttonSend" runat="server"  
        onclick="buttonSend_Click"/>
<asp:Button Text="Recover" id="buttonRecover" runat="server" 
        onclick="buttonRecover_Click"/>

And this is the code behind, in Contact.aspx.cs:

protected void buttonSend_Click(object sender, EventArgs e)
{
    ViewState["name"] = Request.Form["usr"];
    usr.Text=string.Empty;
}
protected void buttonRecover_Click(object sender, EventArgs e)
{
    usr.Text = Convert.ToString(ViewState["name"]);
}

Answer 1

The problem is that Request.Form["usr"] does not exist. The ID of a control is not the same as the Form Post Key (which is the name of an input control).

So either use

ViewState["name"] = Request.Form[usr.UniqueID];

Or the recommended way

ViewState["name"] = usr.Text;