Получение данных из базы

private string CreateJson(IDataReader dataReader)
{
    var list = new List<dynamic>();
    var cnt = dataReader.FieldCount;
    var fields = new List<string>();
    for (int i = 0; i < cnt; i++)
    {
        fields.Add(dataReader.GetName(i));
    }
    while (dataReader.Read())
    {
        dynamic exo = new System.Dynamic.ExpandoObject();
        foreach (var field in fields)
        {
            ((IDictionary<String, Object>)exo).Add(field, dataReader.GetColumnValue(field));
        }
        list.Add(exo);
    }
    return JsonConvert.SerializeObject(list);
}

public string GetSqlTextExample()
{
    var result = "";
    var select = new Select(UserConnection)
            .Column(Column.Asterisk())
        .From("Contact");
    result = select.GetSqlText();
    return result;
}

public string SelectColumns(string tableName, int top)
{
    top = top > 0 ? top : 1;
    var result = "{}";
    var select = new Select(UserConnection)
        .Top(top)
        .Column(Column.Asterisk())
        .From(tableName);
    using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())
    {
        using (IDataReader dataReader = select.ExecuteReader(dbExecutor))
        {
            result = CreateJson(dataReader);
        }
    }
    return result;
}

public string SelectContactsYoungerThan(string birthYear)
{
    var result = "{}";
    var year = DateTime.ParseExact(birthYear, "yyyy", CultureInfo.InvariantCulture);
    var select = new Select(UserConnection)
            .Column("Id")
            .Column("Name")
            .Column("BirthDate")
        .From("Contact")
        .Where("BirthDate").IsGreater(Column.Parameter(year))
            .Or("BirthDate").IsNull()
        .OrderByDesc("BirthDate")
         as Select;
    using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())
    {
        using (IDataReader dataReader = select.ExecuteReader(dbExecutor))
        {
            result = CreateJson(dataReader);
        }
    }
    return result;
}

public string SelectContactsYoungerThanAndHasAccountId(string birthYear)
{
    var result = "{}";
    var year = DateTime.ParseExact(birthYear, "yyyy", CultureInfo.InvariantCulture);
    var select = new Select(UserConnection)
            .Column("Id")
            .Column("Name")
            .Column("BirthDate")
        .From("Contact")
        .Where()
        .OpenBlock("BirthDate").IsGreater(Column.Parameter(year))
            .Or("BirthDate").IsNull()
        .CloseBlock()
        .And("AccountId").Not().IsNull()
        .OrderByDesc("BirthDate")
         as Select;
    using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())
    {
        using (IDataReader dataReader = select.ExecuteReader(dbExecutor))
        {
            result = CreateJson(dataReader);
        }
    }
    return result;
}

public string SelectContactsJoinAccount()
{
    var result = "{}";
    var select = new Select(UserConnection)
            .Column("Contact", "Id").As("ContactId")
            .Column("Contact", "Name").As("ContactName")
            .Column("Account", "Id").As("AccountId")
            .Column("Account", "Name").As("AccountName")
        .From("Contact")
        .Join(JoinType.Inner, "Account")
            .On("Contact", "Id").IsEqual("Account", "PrimaryContactId")
         as Select;
    using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())
    {
        using (IDataReader dataReader = select.ExecuteReader(dbExecutor))
        {
            result = CreateJson(dataReader);
        }
    }
    return result;
}

public string SelectAccountPrimaryContacts()
{
    var result = "{}";
    var select = new Select(UserConnection)
            .Column("Id")
            .Column("Name")
        .From("Contact").As("C")
        .Where()
            .Exists(new Select(UserConnection)
                            .Column("A", "PrimaryContactId")
                        .From("Account").As("A")
                        .Where("A", "PrimaryContactId").IsEqual("C", "Id"))
         as Select;
    using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())
    {
        using (IDataReader dataReader = select.ExecuteReader(dbExecutor))
        {
            result = CreateJson(dataReader);
        }
    }
    return result;
}

public string SelectCountriesWithCitiesCount(int count)
{
    var result = "{}";
    var select = new Select(UserConnection)
            .Column(Func.Count("City", "Id")).As("CitiesCount")
            .Column("Country", "Name").As("CountryName")
        .From("City")
        .Join(JoinType.Inner, "Country")
            .On("City", "CountryId").IsEqual("Country", "Id")
        .GroupBy("Country", "Name")
        .Having(Func.Count("City", "Id")).IsGreater(Column.Parameter(count))
        .OrderByDesc("CitiesCount")
         as Select;
    using (DBExecutor dbExecutor = UserConnection.EnsureDBConnection())
    {
        using (IDataReader dataReader = select.ExecuteReader(dbExecutor))
        {
            result = CreateJson(dataReader);
        }
    }
    return result;
}

public string SelectCountryIdByCityName(string CityName)
{
    var result = "";
    var select = new Select(UserConnection)
            .Column("CountryId")
        .From("City")
        .Where("Name").IsEqual(Column.Parameter(CityName)) as Select;
    result = select.ExecuteScalar<Guid>().ToString();
    return result;
}