using "in" method in where clause with query

[mehmetyildiz]

Hi,
I have an id list that its types are guid. And i am using these ids in my query like below

string whereClause = string.Empty;
                            foreach (var feature in featureSet)
                            {
                                if (feature.Attributes[id] != null)
                                {
                                    if (idList != string.Empty)
                                    {
                                        if (!idList.Contains(feature.Attributes[id].ToString().ToUpper()))
                                            idList += "'{" + feature.Attributes[id].ToString().ToUpper() + "}',";
                                    }
                                    else
                                        idList += "'{" + feature.Attributes[id].ToString().ToUpper() + "}',";
                                }
                            }
                            if (idList != string.Empty)
                                idList = idList.Substring(0, idList.Length - 1);
                            whereClause = wayid+ " IN (" + idList + ")";

with this whereClause i can query succesfully in internetexplorer. But when i try it in mozilla my querytask returns null. And i tried shorter whereClause in mozilla and i could query succesfuly. What should i do for querying with long whereclause espacially using in method. Any Idea?

best regards