How to use ViewState for class objects using C# in ASP.Net

Hi Guys,

I'm Working with ViewState in my project to reduce the cycles of data loading again and again.

It's not working! Please help me

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        if ((object)ViewState["GridView"] != null)
        {
            global_functions.load_gridview(grd_master_district, (object)ViewState["GridView"]);
        }
        else
        {
            load_Grid_View();
        }
    }
}

private void load_Grid_View()
{
    try
    {
        Object obj = ClassBO.load_Master_District();
        ViewState["GridView"] = obj;
        global_functions.load_gridview(grd_master_district, obj);
    }
    catch (Exception ex)
    {
        ex.Message.ToString();
        ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alert", "alert('Something Went Wrong!.')", true);
    }
}