在Log4Net PatternString中添加自定义字段

Question

我正在努力使我的日志模式成为我的公司制定的标准，并可能需要一些帮助。我需要从我的应用程序登录到JSON，所以我把扩展LayoutSkeleton的Json布局放在一起

public class JsonLayout : LayoutSkeleton
{

    public override void ActivateOptions()
    {
    }

    public override void Format(TextWriter writer, LoggingEvent e)
    {
        var dic = new Dictionary<string, object>
        {
            ["level"] = e.Level.DisplayName,
            ["message"] = e.MessageObject,
            ["timestampUtc"] = e.TimeStamp.ToUniversalTime().ToString("O"),
            ["userName"] = e.UserName
        };
        writer.WriteLine(JsonConvert.SerializeObject(dic));
    }
}

并在我的app.config中引用如下

    <appender name="file" type="log4net.Appender.RollingFileAppender,log4net">
        <rollingStyle value="Date" />
        <datePattern value="yyyy-MM-dd" />
        <preserveLogFileNameExtension value="true" />
        <staticLogFileName value="false" />
        <file type="log4net.Util.PatternString" value="c:\\Logs\\.log" />
        <layout type="MyPackage.JsonLayout">
        </layout>
    </appender>

然后当我们登录时，很简单：

Dictionary<string, string> logObject = new Dictionary<string, string>
{
   { "systemId", systemId },
   { "workflowId", workflowId },
   { "transitionName", transitionName },
   { "instrumentId", instrumentId },
   { "instrumentName", instrumentName },
   { "commandId", commandId.ToString() },
   { "message", statusMessage }                    
};
Logger.Info(logObject);

这个很管用。然而，最终被记录下来的是

{
"level": "INFO",
"message": {
    "systemId": "LM9125",
    "workflowId": "WF7656789876",
    "transitionName": "My transition",
    "instrumentId": "LM123",
    "instrumentName": "Centrifuge 1",
    "commandId": "d21fb5fa-5b39-4c43-94cc-72dc6a7a174d",
    "message": "Centrifuge 1 started"
},
"timestampUtc": "2022-05-06T20:23:06.5136166Z",
"userName": "labuser"

}

所请求的是，在记录的消息中，我从message对象中删除嵌套，以便log语句变为

{
  "level": "INFO",
  "systemId": "LM9125",
  "workflowId": "WF7656789876",
  "transitionName": "My transition",
  "instrumentId": "LM123",
  "instrumentName": "Centrifuge 1",
  "commandId": "d21fb5fa-5b39-4c43-94cc-72dc6a7a174d",
  "message": "Centrifuge 1 started",
  "timestampUtc": "2022-05-06T20:23:06.5136166Z",
  "userName": "labuser"
}

我已经更新了格式方法

...
var dic = new Dictionary<string, object>
{
   ["level"] = e.Level.DisplayName,
   ["systemId"] = "",
   ["workflowId"] = "",
   ["transitionName"] = "",
   ["instrumentId"] = "",
   ["instrumentName"] = "",
   ["message"] = e.MessageObject,
   ["timestampUtc"] = e.TimeStamp.ToUniversalTime().ToString("O"),
   ["userName"] = e.UserName
 };
 writer.WriteLine(JsonConvert.SerializeObject(dic));
 ...

我似乎想不出的是如何从e.MessageObject中提取值，以便将值放入必要的字段中。在调试器中，我可以看到e.MessageObject是object {System.Collections.Generic.Dictionary<string, string>}类型的。

当我试图像普通字典一样使用e.MessageObject["systemId"]访问它时，我会得到以下错误消息error CS0021: Cannot apply indexing with [] to an expression of type 'object'。我不是.NET程序员，无法找到解决这个愚蠢错误的方法。请帮帮我！

我搜索了堆栈溢出，找到的最接近的答案是this。但这对解决这个问题毫无帮助。

Answer 1

object是一种泛型类型，意思是“我可以在这里存储几乎任何类型的东西”。所以编译器不知道会有哪种类型，所以它拒绝将索引语义应用到它。

你需要让编译器知道你在处理什么样的对象.

与…有关的东西：

Dictionary<string,string> messages = e.MessageObject as Dictionary<string,string>;
if(null == messages) {
    // The thing stored here is NOT a Dictionary<string,string>.
    throw new Exception("not the right type");
}
// code to work with the Dictionary...  messages["systemId"]