ASP.Net มีปัญหาตอนการอัพเดทรูปภาพครับ โดยจากเดิมเมื่อทำการแก้ไขข้อมูล จะลบไฟล์ภาพเก่าทิ้งแล้วอัพภาพใหม่แทนที่

protected void BTSave_Click(object sender, EventArgs e)
        {
            if (this.FormMode == StateMode.Add)
            {
                string MaxID = eq.SelectMaxID().Rows[0]["maxid"].ToString();
                if (MaxID.ToString() == "")
                {
                    ViewState["AUTOGEN"] = "EQU001";
                }
                else
                {
                    string sub = MaxID.Substring(3);
                    int num = Convert.ToInt32(sub);
                    num += 1;
                    string str = Convert.ToString(num);
                    string autogen = "EQU" + str.PadLeft(3, '0');
                    ViewState["AUTOGEN"] = autogen;
                }
                eq._EQUIPMENTID = ViewState["AUTOGEN"].ToString();
                eq._EQUIPMENTNAME = EqNametxt.Text + " " + Session["model_name"].ToString();
                eq._MODELID = DbModelEQ.SelectedValue;
                eq._EQUIPMENTDETAIL = EqDetailtxt.Text;
                eq.InsertEquipment();

                File.Move(Server.MapPath("~/ImageUpload/") + "tempimg" + Session["id"] + "EQU.jpg", Server.MapPath("~/ImageUpload/") + ViewState["AUTOGEN"].ToString() + "PIC.jpg");
                this.FormMode = StateMode.Search;
                View_Grid();
                SetScreen();
                Server.Transfer("Equipment.aspx");
            }
            else if (this.FormMode == StateMode.Edit)  ///ส่วนการแก้ไขข้อมูลครับ
            {
                eq._EQUIPMENTID = ViewState["equipment_id"].ToString();
                eq._EQUIPMENTNAME = EqNametxt.Text;
                eq._MODELID = DbModelEQ.SelectedValue;
                eq._EQUIPMENTDETAIL = EqDetailtxt.Text;
                eq.UpdateEquipment();
                File.Delete(Server.MapPath("~/ImageUpload/") + ViewState["equipment_id"].ToString() + "PIC.jpg");  
                File.Move(Server.MapPath("~/ImageUpload/") + "tempimg" + Session["id"] + "EQU.jpg", Server.MapPath("~/ImageUpload/") + ViewState["equipment_id"].ToString() + "PIC.jpg");
                
                this.FormMode = StateMode.Search;
                View_Grid();
                SetScreen();
                Server.Transfer("Equipment.aspx");
            }
        }