Unable to cast object of type 'System.String' to type 'System.Byte[]'.how to solve?

public void ProcessRequest (HttpContext context) 
    {
       // SqlConnection cn = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString);
        SqlConnection cn = new SqlConnection(ConfigurationManager.AppSettings["constring"].ToString());
        cn.Open();
        
      string sql = "Select clogo from tbl_company1 where cid=@cid";
        SqlCommand cmd = new SqlCommand(sql, cn);
       cmd.Parameters.Add("@cid", SqlDbType.Int).Value = context.Request.QueryString["cid"];
       cmd.Prepare();
        SqlDataReader dr = cmd.ExecuteReader();
       dr.Read();
       //context.Response.ContentType = dr["imagename"].ToString();
       context.Response.BinaryWrite((byte[])dr["clogo"]);//error is here like "Unable to cast object of type 'System.String' to type 'System.Byte[]'"//
       dr.Close();
       cn.Close(); 
        
   }