Question

如何识别具有多个OR条件的if语句中哪个条件失败。示例如下。

if ((null == emailNotificationData || string.IsNullOrEmpty(emailNotificationData.Sender))
                        || null == emailNotificationData.ToRecipients)
  {
    LogProvider.Log(typeof(Notification), LogLevel.Error, "Error sending the email notification 'Here i want to log failed argument'");
    return;
  }

Answer 1

如果不重新检查每个条件，你就不能。我只想把它写成：

if (emailNotificationData == null)
{
    // This is a helper method calling LogProvider.Log(...)
    LogEmailNotificationError("No email notification data");
    return;
}
if (string.IsNullOrEmpty(emailNotificationData.Sender))
{
    LogEmailNotificationError("No sender");
    return;
}
if (emailNotificationData.ToRecipients == null)
{
    LogEmailNotificationError("No recipients");
    return;
}

您可以将此提取到您的通知数据类型的ValidateAndLog扩展方法中 - 使其成为扩展方法意味着您也可以将其处理为null：

// ValidateAndLog returns true if everything is okay, false otherwise.
if (!emailNotificationData.ValidateAndLog())
{
    return;
}

这样就不需要混淆其他代码了。

请注意，C＃写作几乎没有任何好处：

if (null == x)

...除非您实际比较布尔值，否则优先进行常量优先比较的“正常”原因（捕捉=的{{1}}的拼写错误）不适用，无论如何==都不会编译。

Answer 2

使用多个if或有意义的bool变量：

bool noEmailData = emailNotificationData == null;
bool noEmailSender = string.IsNullOrEmpty(emailNotificationData.Sender);

if(noEmailData || noEmailSender)
{
    string msg = string.Format("Error sending the email notification: {0} {1}."
        , noEmailData ? "No email-data available" : ""
        , noEmailSender ? "No email-sender available" : "");
    LogProvider.Log(typeof(Notification), LogLevel.Error, msg);
}

这通常会提高可读性。

Answer 3

您可以创建验证规则来检查emailNotificationData。

public class Rule<T>
{
    public Func<T, bool> Test { get; set; }

    public string Message { get; set; }
}

然后，您创建一个类，为您定义emailNotificationData的规则。

public class EmailNotificationValidationRules
{
    public static IEnumerable<Rule<EmailNotificationData>> Rules 
    {
        get
        {
            return new List<Rule<EmailNotificationData>>
                {
                    new Rule<EmailNotificationData> { Test = data => data != null, Message = "No email notifacation data" },
                    new Rule<EmailNotificationData> { Test = data => !string.IsNullOrEmpty(data.Sender), Message = "No sender" },
                    new Rule<EmailNotificationData> { Test = data => data.ToRecipients != null, Message = "No recipients" }
                };
        }
    }
}

现在您可以使用此代码检查您的对象

        bool isValid = EmailNotificationValidationRules.Rules.All(rule => rule.Test(emailNotificationData));

        if (isValid == false)
        {
            var failedRules = EmailNotificationValidationRules.Rules.Where(rule => rule.Test(emailNotificationData) == false);
            var text2Log = failedRules.Aggregate(new StringBuilder(), (builder, rule) => builder.AppendLine(rule.Message), builder => builder.ToString());
        }

字段text2log仅包含失败规则的消息。

如何在具有多个OR条件的if语句中识别哪个条件失败？

3 个答案: