Question

是否有像switch语句一样的C＃结构允许控制进入下一级别？我有这样的事情：

    public static IEnumerable<string> SeverityOrHigher(string severity)
    {
        var result = new List<string>();

        switch (severity.ToUpper())
        {
            case "ALL":
                result.Add("ALL");
            case "DEBUG":
                result.Add("DEBUG");
            case "INFO":
                result.Add("INFO");
            case "WARN":
                result.Add("WARN");
            case "ERROR":
                result.Add("ERROR");
            case "FATAL":
                result.Add("FATAL");
            case "OFF":
                result.Add("OFF");
            default:
                break;
        }

        return result;
    }

...这显然不适用于C＃，（Control cannot fall through from one case label...）但在我看来应该是这样。我知道它预计会有中断，但这不会给我提供我正在寻找的数据流。可以采取哪些措施来实现我想要的方式？

Answer 1

在你的情况下，你可以用一点LINQ来模仿“坠落的情况”：

public static IEnumerable<string> SeverityOrHigher(string severity)
{
    var result = new List<string>() 
        { "ALL", "DEBUG", "INFO", "WARN", "ERROR", "FATAL", "OFF" };
    return result.SkipWhile(l => l != severity.ToUpper()).ToArray();
}

Answer 2

与gotos等一起，你可以使用这个枚举和一点linq：

    public static IEnumerable<Severity> SeverityOrHigher(Severity severity)
    {
        var value = (int) severity;

        return Enum.GetValues(typeof (Severity))
            .Cast<int>()
            .Where(i => i >= value)
            .Select(i => (Severity) i);
    }

    public enum Severity
    {
        All = 0,
        Trace = 1,
        Debug = 2,
        Information = 3,
        Warning = 4,
        Error = 5,
        Fatal = 6
    }

Answer 3

这不是最佳解决方案，但您可以使用goto语句，如下所示：

switch (severity.ToUpper())
{
  case "ALL":
    result.Add("ALL");
    goto case "DEBUG";
  case "DEBUG":
    result.Add("DEBUG");
    goto case "INFO";
  case "INFO":
    result.Add("INFO");
    goto case "WARN";
  case "WARN":
    result.Add("WARN");
    goto case "ERROR";
  case "ERROR":
    result.Add("ERROR");
    goto case "FATAL";
  case "FATAL":
    result.Add("FATAL");
    goto case "OFF";
  case "OFF":
    result.Add("OFF");
    break;
  default:
    break;
}

Answer 4

使用转到：

        switch (severity.ToUpper())
        {
            case "ALL":
                result.Add("ALL");
                goto case "DEBUG";
            case "DEBUG":
                result.Add("DEBUG");
                goto case "INFO";
            case "INFO":
                result.Add("INFO");
                goto case "WARN";
            case "WARN":
                result.Add("WARN");
                goto case "ERROR";
            case "ERROR":
                result.Add("ERROR");
                goto case "FATAL";
            case "FATAL":
                result.Add("FATAL");
                goto case "OFF";
            case "OFF":
                result.Add("OFF");
                break;
            default:
                break;
        }

Microsoft（隐式）建议使用此方法：http://msdn.microsoft.com/en-us/library/06tc147t(v=vs.71).aspx

Answer 5

@ nemesv的Linq答案是更好的解决方案，但是如果你想用开关来做，你可以这样做，并得到相同的结果。

public static IEnumerable<string> SeverityOrHigher(string severity)
{
  var lastFound = -1;

  var severityList = new List<string>() { "ALL", "DEBUG", "INFO", "WARN", "ERROR", "FATAL", "OFF" };
  var results = new List<string>();

  foreach (var t in severityList)
  {

    if (lastFound > -1)
    {
      for (var index = lastFound + 1; index < severityList.Count; index++)
      {
        results.Add(severityList[index]);
      }
      return results;
    }

    switch (severity.ToUpper())
    {
      case "ALL":
        results.Add(severity);
        lastFound = 0;
        break;
      case "DEBUG":
        lastFound = 1;
        results.Add(severity);
        break;
      case "INFO":
        lastFound = 2;
        results.Add(severity);
        break;
      case "WARN":
        lastFound = 3;
        results.Add(severity);
        break;
      case "ERROR":
        lastFound = 4;
        results.Add(severity);
        break;
      case "FATAL":
        lastFound = 5;
        results.Add(severity);
        break;
      case "OFF":
        lastFound = 6;
        results.Add(severity);
        break;
    }
  }

  return results;
}

<强>测试

  var list = SeverityOrHigher("ALL");
  foreach (var severity in list)
  {
    Console.WriteLine(severity);
  }

  Console.ReadKey();

Answer 6

看起来不太好，但可以为你完成这项工作：

string s = severity.ToUpper();
result.add("OFF");
if (s == "OFF")
  return result;
result.add("FATAL");
if (s == "FATAL")
  return result;
result.add("ERROR");
if (s == "ERROR")
  return result;
// ...
result.add("ALL");
return result;

Answer 7

我会选择创建另一个表示所有有效严重性的列表，并检查输入严重性是否为其中之一：

public static IEnumerable<string> SeverityOrHigher(string severity)
{
    var result = new List<string>();
    var severities = new List<string> { "ALL", "DEBUG", "INFO", "WARN", "ERROR", "FATAL", "OFF" };

    severity = severity.ToUpper();

    if (severities.Contain(severity))
            result.Add(severity);

    return result;
}

我想要一些像switch语句（但当然不同）

7 个答案: