how to display previous price in gridview

protected void btnadd_Click(object sender, EventArgs e)

    {

     string totalPid = txtcname.Text.Trim().ToUpper() + "-" + txtcid.Text.Trim();
    int? InsertProductdetStatus;
    objProductsPL.prodName = totalPid;
    objProductsPL.productname = txtname.Text.Trim().ToString();
    objProductsPL.unitweight = Convert.ToInt32(txtunit.Text.ToString());
    objProductsPL.company = txtcompany.Text.ToString();
    objProductsPL.purpose = (txtpurpose.Text.Trim().ToString()== "" ? null : txtpurpose.Text.Trim());
    objProductsPL.producttype = ddlproducttype1.SelectedItem.Text.ToString();
    objProductsPL.unitprice = Convert.ToDouble(txtunitprice.Text.ToString());
    objProductsPL.productid3 = ddlctype.SelectedItem.Text.ToString();
    objProductsPL.username = Session["username"].ToString();
    InsertProductdetStatus = objProductsBAL.ProductidDetInsert(objProductsPL);
    if (InsertProductdetStatus.Equals(1))
    {
        ScriptManager.RegisterClientScriptBlock(this.Page, this.GetType(), "UpdateDetails", "alert('Details Already Exist');", true);

    }
    else if (InsertProductdetStatus.Equals(2))
    {


    ScriptManager.RegisterClientScriptBlock(this.Page, this.GetType(), "UpdateDetails", "alert('Added Successfully');", true);
        Grid();
        clear();
        bindRate();
    }


}