Question

对于UiPath版本18.2.3，我成功创建了一个新的日志记录活动。这个想法是，在将所有内容记录在Orchestrator中时，新活动还将另外记录一个文件。即将加入我们的组织将升级到UiPath 2019.4.3，但是我的活动无法正常进行，因此我需要将UiPath引用升级到当前的dlls。这样做为我提供了可编译的代码，但是活动导致null-pointer exception。为什么？

这是我的代码：

using System;
using System.Activities;
using System.Activities.Presentation.Metadata;
using System.ComponentModel;
using System.IO;
using System.Text;
using UiPath.Core.Activities;

namespace CustomCode.Log
{
    /// <summary>
    /// Designer attribute gives a look & feel like UiPaths own LogMessage activity
    /// </summary>
    [Designer(typeof(UiPath.Core.Activities.Design.LogDesigner))]
    public class LogMessage : CodeActivity, IRegisterMetadata
    {
        [Category("Input")]
        public CurentLogLevel Level { get; set; }

        [Category("Input")]
        public InArgument<System.String> Message { get; set; }

        [Category("Input")]
        public InArgument<System.String> LogFilePath { get; set; }

        /// <summary>
        /// UiPath Log Message object reference
        /// </summary>
        private UiPath.Core.Activities.LogMessage _LogMessage { get; set; }

        /// <summary>
        /// Constructor
        /// </summary>
        public LogMessage()
        {
            DisplayName = "Extended Log Message";            
            Level = CurentLogLevel.Trace; // default setting
        }

        /// <summary>
        /// declare dummy register metadata class to force UiPath to load this assembly
        /// </summary>
        public void Register()
        {
            // intentionally empty
        }

        /// <summary>
        /// First log as if done by native UiPath then log to the file specified
        /// </summary>
        /// <param name="context"></param>
        protected override void Execute(CodeActivityContext context)
        {
            // first do the usual UiPath logging...
            string message = Message.Get(context);
            //bool isNew = false;

            #region log as UiPath standard
            // it is necessary to create new objects every time. 
            // reassigning property values causes errors when logging is frequent...
            _LogMessage = new  UiPath.Core.Activities.LogMessage
            {
                Level = this.Level,
                Message = new InArgument<string>(message),
            };

            // do UiPath log 
            try
            {
                WorkflowInvoker.Invoke(_LogMessage); // NULL POINTER EXCEPTION HERE
            }
            catch (Exception ex)
            {
                throw new Exception("Internal UiPath Invoke Exception ", ex);
            }
            #endregion

            string logFilePath = LogFilePath.Get(context);

            // log to file if path is specified...
            if (logFilePath != null)
            {
                LogToFile(logFilePath, message, Level.ToString());
            }
        }

        /// <summary>
        /// Method to write a line in the log file
        /// </summary>
        /// <param name="filename">the file to which to log</param>
        /// <param name="message">the log message</param>
        /// <param name="level">the log level</param>
        private void LogToFile(string filename, string message, string level)
        {
            StringBuilder LogLine = new StringBuilder(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));
            LogLine.Append("\t");
            LogLine.Append(level);
            LogLine.Append("\t");

            LogLine.Append("\t - ");
            LogLine.Append(message);
            LogLine.Append(Environment.NewLine);

            try
            {
                // append the log line
                File.AppendAllText(filename, LogLine.ToString());
            }
            catch (Exception ex)
            {
                // try to log the exception in UiPath
                _LogMessage.Message = new InArgument<string>(ex.Message + Environment.NewLine + ex.StackTrace);
                throw new Exception("Internal append to log file exception", ex);
            }
        }
    }
}

Answer 1

您的错误表明 _LogMessage 为空，因此为空指针错误。

您可以通过简单地检查部分代码来验证这一点

_LogMessage = new  UiPath.Core.Activities.LogMessage
            {
                Level = this.Level,
                Message = new InArgument<string>(message),
            };

如果您的变量为空：

if (_LogMessage.Any())

希望这会有所帮助。

从C＃执行UiPath活动会导致空指针异常

1 个答案: