Question

大家好！
我问了一次熟悉的问题，现在又被卡住了
什么是重构这个的更好方法？
PS。不希望将查询作为参数传递，搜索最优雅的解决方案

方法1

public static List<string> GetWinners(Prize prize)
    {
        List<string> winners = new List<string>();

        using (OleDbConnection connection = new OleDbConnection(ConfigurationManager.ConnectionStrings["ForteLotteryDataConnectionString"].ConnectionString))
        {
            var query = string.Concat(
                @"
                    SELECT Member.IBAN ",
                    "FROM Member, Summary ",
                    "WHERE Member.ID = Summary.WinnerID ",
                    "AND PrizeID = " + prize.ID
            );

            connection.Open();
            OleDbCommand command = new OleDbCommand(query, connection);
            OleDbDataReader reader = command.ExecuteReader();

            ...

            connection.Close();
        }

        return winners;
    }

方法2

    public static List<string> GetDoubles(Prize prize)
    {
        List<string> doubles = new List<string>();

        using (OleDbConnection connection = new OleDbConnection(ConfigurationManager.ConnectionStrings["ForteLotteryDataConnectionString"].ConnectionString))
        {
            var query = string.Concat(
                @"
                    SELECT Member.IBAN ",
                    "FROM Member, Summary ",
                    "WHERE Member.ID = Summary.DoubleID ",
                    "AND PrizeID = " + prize.ID
            );

            connection.Open();
            OleDbCommand command = new OleDbCommand(query, connection);
            OleDbDataReader reader = command.ExecuteReader();

            ...

            connection.Close();
        }

        return doubles;
    }

Answer 1

使用String.Format并将propname作为参数传递：

    public static List<string> GetSomething(string propName, Prize prize)
    {
        List<string> doubles = new List<string>();

        using (OleDbConnection connection = new OleDbConnection(ConfigurationManager.ConnectionStrings["ForteLotteryDataConnectionString"].ConnectionString))
        {
            var query = string.Format(
                @"SELECT Member.IBAN,
                    FROM Member, Summary,
                    WHERE Member.ID = Summary.{0},
                    AND PrizeID = {1}", propName, prize.ID
            );

            connection.Open();
            OleDbCommand command = new OleDbCommand(query, connection);
            OleDbDataReader reader = command.ExecuteReader();

            ...

            connection.Close();
        }

        return doubles;
    }

顺便说一句 - 请注意SQLI＆＃39; s - 阅读parameterized queries。

Answer 2

好吧，你可以传递你想要的类型作为枚举，并阅读它。它看起来像这样：

enum Target { DOUBLES, WINNERS } // add as many as you want.

public static List<string> GetTarget(Prize prize, Target lookingFor)
{
....
// define the query
    switch(lookingFor) // take care of each case in the enum.
    {
     case Target.DOUBLES:
       query = string.Concat(
            @"
                SELECT Member.IBAN ",
                "FROM Member, Summary ",
                "WHERE Member.ID = Summary.DoubleID ",
                "AND PrizeID = " + prize.ID
        );
        break;
      case Target.WINNERS:
        query = string.Concat(
            @"
                SELECT Member.IBAN ",
                "FROM Member, Summary ",
                "WHERE Member.ID = Summary.WinnerID ",
                "AND PrizeID = " + prize.ID
        );
        break;
       default: // in case you got a bad value
           //throw an exception
        break;

    }
//Do stuff with the query.
}

Answer 3

方法1

public static List<string> GetWinners(Prize prize)
{
    List<string> winners = new List<string>();

    using (OleDbConnection connection = new OleDbConnection(ConfigurationManager.ConnectionStrings["ForteLotteryDataConnectionString"].ConnectionString))
    {
        var query = string.Concat(
            @"
                SELECT Member.IBAN ",
                "FROM Member, Summary ",
                "WHERE Member.ID = Summary.WinnerID ",
                "AND PrizeID = " + prize.ID
        );

        connection.Open();
        OleDbCommand command = new OleDbCommand(query, connection);
        OleDbDataReader reader = command.ExecuteReader();

        ...

        connection.Close();
    }

    return winners;
}

<强>方法2

public static List<string> GetDoubles(Prize prize)
    {
        List<string> doubles = new List<string>();

        using (OleDbConnection connection = new OleDbConnection(ConfigurationManager.ConnectionStrings["ForteLotteryDataConnectionString"].ConnectionString))
        {
            var query = string.Concat(
                @"
                    SELECT Member.IBAN ",
                    "FROM Member, Summary ",
                    "WHERE Member.ID = Summary.DoubleID ",
                    "AND PrizeID = " + prize.ID
            );

            connection.Open();
            OleDbCommand command = new OleDbCommand(query, connection);
            OleDbDataReader reader = command.ExecuteReader();

            ...

            connection.Close();
        }

        return doubles;
    }

加入这些方法

protected void JoinMethods()
        {
            List<string> j = new List<string>();
            j.AddRange(this.GetWinners("Parameters goes here"); //Method 2
            j.AddRange(this.GetDoubles("Parameters goes here"); //Method 2          
        }

Answer 4

我宁愿列举可能的案例（enum WinnerKind），类似的事情：

public enum WinnerKind {
  Winner = 0,
  Double = 1
}

...

public static List<string> GetWinnersData(Prize prize, WinnerKind kind) {
  List<string> result = new List<string>();

  // You don't have to concat strings
  // it's a good practice to use parametrized queries: "PrizeID = ?" 
  String query = String.Format(
    @"SELECT Member.IBAN,
        FROM Member, 
             Summary,
       WHERE Member.ID = {0}
         AND PrizeID = ?",
    kind == WinnerKind.Winner ? "Summary.WinnerID" : "Summary.DoubleID");

  using (OleDbConnection connection = new OleDbConnection(ConfigurationManager.ConnectionStrings["ForteLotteryDataConnectionString"].ConnectionString)) {
    connection.Open();

    using (OleDbCommand command = new OleDbCommand(query, connection)) {
      // named parameters aren't supported
      command.Parameters.Add(prize.ID);

      using (OleDbDataReader reader = command.ExecuteReader()) {
        while (reader.Read()) 
          result.Add(Convert.ToString(reader[0].GetValue()));
      }
    } 
  }

  return result;  
}

public static List<string> GetWinners(Prize prize) {
  return GetWinnersData(prize, WinnerKind.Winner);
}

public static List<string> GetDoubles(Prize prize) {
  return GetWinnersData(prize, WinnerKind.Double);
}

我应该如何合并这两种方法？

4 个答案: