using System;

using System.Collections.Generic;

using System.Text;

using System.Linq;

public class Program

{

    static string MontarSqlComCondicoes(string tabela, string c1, string c2, bool and)

    {

        var condicoes = new List<string>();

        var sql = new StringBuilder();

        sql.Append("select * from")

            .Append(" ")

            .Append(tabela)

            .Append(" ");

        if (!string.IsNullOrWhiteSpace(c1))

        {

            condicoes.Add(c1);

        }

        if (!string.IsNullOrWhiteSpace(c2))

        {

            condicoes.Add(c2);

        }

        if (condicoes.Any())

        {

            sql.Append("where")

                .Append(" ");

            if (and) sql.Append(string.Join(" and ", condicoes.ToArray()));

            else sql.Append(string.Join(" or ", condicoes.ToArray()));

        }

        return sql.ToString();

    }

    public static void Main()

    {

        var sql = MontarSqlComCondicoes("pessoa", "nome = @nome", "idade > @idade", true);

        Console.WriteLine(sql);

    }

}