Change background color of ASP.Net GridView Row based on cell value

HTML

    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns = "false" OnRowDataBound = "OnRowDataBound">
    <Columns>
        <asp:BoundField DataField = "Item" ItemStyle-CssClass = "Item"/>
        <asp:TemplateField>
        <ItemTemplate>
            <asp:TextBox ID="txtPrice" CssClass = "Price" runat="server" Text = '<%# Eval("Price") %>'></asp:TextBox>
        </ItemTemplate>
        </asp:TemplateField>
    </Columns>
    </asp:GridView>

Code

protected void Page_Load(object sender, EventArgs e)
    {

        if (!Page.IsPostBack)
        {
            DataTable dt = new DataTable();
            dt.Columns.AddRange(new DataColumn[2] { new DataColumn("Item"), new DataColumn("Price") }); 
            dt.Rows.Add("Shirt", 0);
            dt.Rows.Add("Football", 1000);
            dt.Rows.Add("Bat", 500);
            GridView1.DataSource = dt;
            GridView1.DataBind();            
        }

    }
    protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            switch ((e.Row.FindControl("txtPrice") as TextBox).Text)
            {
                case "0":
                    e.Row.BackColor = Color.Red;
                    break;
                case "1000":
                    e.Row.BackColor = Color.Green;
                    break;
                case "500":
                    e.Row.BackColor = Color.Blue;
                    break;
            }          
        }
    }