How do I solve updating problem in webform. Able to insert but not update.

if (btn_add.Text == "Submit")
        {
            string BracketSuspensionType = Convert.ToString(txt_BracketSuspensionType.Text.Trim());
            string PoleTypeID = Convert.ToString(dd_PoleTypeID.SelectedValue.Trim());
            string Status = chk_Active.Checked ? "True" : "False";
            System.Collections.Hashtable ht = (System.Collections.Hashtable)Session["UserDetails"];
            Int64 UsrId = (Int64)ht["UserID"];
            string CreatedBy = Convert.ToString(UsrId);
            //string CreatedOn = DateTime.Now;
            string filename = Path.GetFileName(fileuploadimages.PostedFile.FileName);
            fileuploadimages.SaveAs(Server.MapPath("~/Images/Bracket Type/" + filename));
            try
            { 
            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["valmont"].ToString());
            con.Open();
            SqlCommand cmd = new SqlCommand("Insert into DEF_BRACKET_ACCESSORIES_MST(BracketSuspensionType,PoleTypeID,Status,CreatedBy,ImagePath) values(@BracketSuspensionType,@PoleTypeID,@Status,@CreatedBy,@ImagePath)", con);

            cmd.Parameters.AddWithValue("@BracketSuspensionType", BracketSuspensionType);
            cmd.Parameters.AddWithValue("@PoleTypeID", PoleTypeID);
            cmd.Parameters.AddWithValue("@Status", Status);
            cmd.Parameters.AddWithValue("@CreatedBy", CreatedBy);
            //cmd.Parameters.AddWithValue("@CreatedOn", CreatedOn);
            cmd.Parameters.AddWithValue("@ImagePath", "~/Images/Bracket Type/" + filename);
            cmd.ExecuteNonQuery();
            con.Close();
           }
else if (btn_add.Text == "Update")

{
grv_BracketAccessories.EditIndex = -1;
            string AccessoryID = Convert.ToString(txtAccessoryID.Text);
            //string AccessoryID = txtAccessoryID.Text;
            string BracketSuspensionType = Convert.ToString(txt_BracketSuspensionType.Text.Trim());
            string PoleTypeID = Convert.ToString(dd_PoleTypeID.SelectedValue.Trim());
            string Status = chk_Active.Checked ? "True" : "False";
            System.Collections.Hashtable ht = (System.Collections.Hashtable)Session["UserDetails"];
            Int64 UsrId = (Int64)ht["UserID"];
            string CreatedBy = Convert.ToString(UsrId);
            //string CreatedOn = DateTime.Now;
            string filename = Path.GetFileName(fileuploadimages.PostedFile.FileName);
            fileuploadimages.SaveAs(Server.MapPath("~/Images/Bracket Type/" + filename));

            try
            {
                SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["valmont"].ToString());
                con.Open();
                //SqlCommand cmd = new SqlCommand("Update DEF_BRACKET_ACCESSORIES_MST(BracketSuspensionType,PoleTypeID,Status,CreatedBy,ImagePath) values(@BracketSuspensionType,@PoleTypeID,@Status,@CreatedBy,@ImagePath)", con);
                SqlCommand cmd = new SqlCommand("Update DEF_BRACKET_ACCESSORIES_MST set BracketSuspensionType=@BracketSuspensionType,PoleTypeID=@PoleTypeID,Status=@Status,CreatedBy=@CreatedBy,ImagePath=@ImagePath WHERE AccessoryID=@AccessoryID", con);
                cmd.Parameters.AddWithValue("@BracketSuspensionType", BracketSuspensionType);
                cmd.Parameters.AddWithValue("@PoleTypeID", PoleTypeID);
                cmd.Parameters.AddWithValue("@Status", Status);
                cmd.Parameters.AddWithValue("@CreatedBy", CreatedBy);
                //cmd.Parameters.AddWithValue("@CreatedOn", CreatedOn);
                cmd.Parameters.AddWithValue("@ImagePath", "~/Images/Bracket Type/" + filename);
                cmd.Parameters.AddWithValue("@AccessoryID", AccessoryID);
                cmd.ExecuteNonQuery();
                con.Close();
}

CREATE TABLE [dbo].[DEF_BRACKET_ACCESSORIES_MST](
	[AccessoryID] [bigint] IDENTITY(1,1) NOT NULL,
	[BracketSuspensionType] [varchar](70) NOT NULL,
	[Status] [bit] NOT NULL,
	[CreatedBy] [bigint] NULL,
	[CreatedOn] [datetime] NULL,
	[UpdatedBy] [bigint] NULL,
	[UpdatedOn] [datetime] NULL,
	[PoleTypeID] [bigint] NOT NULL,
	[column1] [varchar](100) NULL,
	[column2] [varchar](100) NULL,
	[column3] [varchar](100) NULL,
	[ImagePath] [varchar](max) NULL,
 CONSTRAINT [PK__DEF_BRAC__3214EC270D7A0286] PRIMARY KEY CLUSTERED 
(
	[AccessoryID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO