Web Forms :: ListBox Selected Item Costing To Business Object

I want to cast back my ListBox Item into my Business Object. Following is the code. ListBox Populate Code on Page Load...

if (!Page.IsPostBack)
{
SalesDBEntities ctx = new SalesDBEntities();
this.ListBox1.DataSource = ctx.SalesHistories;
this.ListBox1.DataTextField = "Product";
this.ListBox1.DataValueField = "SaleID";
this.ListBox1.DataBind();
}

And here is

protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e)
{
SalesHistory sh = new SalesHistory();
//sh = (SalesHistory)ListBox1.SelectedValue; Error Here. How it is possible
TextBox1.Text = ListBox1.SelectedValue.ToString();
}