How to disable a link button in Gridview when clicked on it

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C#

ASP.NET

I have two Link buttons in GridView Approve and Reject I want Approve linkButton to be disabled when i click on it. I tried the following code but its not working.

protected void gvManagerTimeSheet_RowCommand(object sender, GridViewCommandEventArgs e)

{

        if (e.CommandName == "ApproveRow")
        {
            GridViewRow row = (GridViewRow)(((LinkButton)e.CommandSource).NamingContainer);
            LinkButton lnkbtn = (LinkButton)row.FindControl("lbApprove");
            lnkbtn.Enabled = false;

            int rowIndex = ((GridViewRow)((LinkButton)e.CommandSource).NamingContainer).RowIndex;
            int TimeSheetId = Convert.ToInt32(e.CommandArgument);

            string CS = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;

            using (SqlConnection con = new SqlConnection(CS))
            {
                SqlCommand cmd = new SqlCommand("spApproveTimeSheet ", con);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@TimeSheetId", TimeSheetId);

                con.Open();
                cmd.ExecuteNonQuery();

                GetManagerTimeSheets();
            }

        }