I am working with a legacy database which uses WIN1251 text columns (don't ask me why). I am now trying to read data through the FirebirdClient 7.1.1.0 (and earlier versions) but characters like é and ë are replaced by question marks. I have tried connection character set NONE, UTF8 and even WIN1251 but to the same effect.

I tested this with WIN1252 columns, and that works fine with connection character set NONE, WIN1252 or UTF8. Is WIN1251 not supported?

Sample code (sensitive info removed):

using (FbConnection connection = new FbConnection(@"character set=UTF8;data source=localhost;initial catalog=<db path>;user id=<user>;password=<pass>")) {
                connection.Open();
                using (var command = new FbCommand(@"select id, name from client", connection))
                {
                    using (var reader = command.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            Console.WriteLine($"ID {(int)reader["ID"]}, NAME {(string)reader["NAME"]}");
                        }
                    }
                }
            }