How can I pass a data string to a programmatically loaded custom user control in C#

UserControl myUC = (UserControl).Load("~/customUserControl.ascx");

Bob b = (Bob).Load("~/customUserControl.ascx");

class Bob : UserControl{
public string User { get; set;}
}

b.User = theuser;

MyUserControl myUCTyped = (MyUserControl)myUC;
myUCTyped.ThePublicProperty = "some value";

MyUserControl myUC = (UserControl).Load("~/customUserControl.ascx") as MyUserControl;
string result = myUC.user;

public partial class todo : System.Web.UI.UserControl
{
    private string mysecondteststring;
    public string setValue
    {
        get
        {
            return mysecondteststring;
        }
        set
        {
            mysecondteststring = value;
        }
    }
    protected void Page_Load(object sender, EventArgs e)
    {
        // my code
    }
}