如何访问ascx控件的codebehind对象中的公共变量？(内联表达式)

public string MyVariable { get; set; }

<%= MyVariable %>

<asp:TextBox ID="txtMyVariable" runat="server" Text='<%# MyVariable %>'></asp:TextBox>

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        DataBind();
    }
}

protected void btnSave_Click(object sender, EventArgs e)
{
    MyVariable = txtMyVariable.Text;
    DataBind();
}