NLog-写入数据库时​​未传递给查询的参数

Question

I'm pretty new to NLog so please forgive my basic question.

I've inherited a Winforms application written by some contractors, I'm mainly a database developer but I've managed to do some development of the application but I sometimes struggle with tracking down error messages encountered by users, therefore I'm attempting to retrofit logging into the application via NLog, I first encountered the issue in NLog 4.4.5 and I've since updated to 4.4.12 and that hasn't solved the problem. I've verified that NLog is catching the errors correctly as it will output to a text file but when I try to direct it to a database output I can't get it to work.

This is my database table:

My problem is that I can only get errors written to the database only if I don't pass any parameters to the insert statement (which is pretty useless). That is to say that the following in my NLog.config file works:

<target name="database" xsi:type="Database">
  <commandText>INSERT INTO [tblException] (DbVersionID, ExceptionDateTime) SELECT MAX(DbVersionID), GETDATE() FROM tblDbVersion</commandText>

  <dbProvider>System.Data.SqlServerCe.4.0</dbProvider>
  <connectionString>Data Source=${basedir}\Database.sdf</connectionString>
</target>

But this doesnt':

<target name="database" xsi:type="Database">
   <commandText>INSERT INTO [tblException] (DbVersionID, ExceptionDateTime, Message) SELECT MAX(DbVersionID), GETDATE(), @message FROM tblDbVersion</commandText>

   <parameter name="@message" layout="${message}" />

   <dbProvider>System.Data.SqlServerCe.4.0</dbProvider>
   <connectionString>Data Source=${basedir}\Database.sdf</connectionString>
</target>

I've enabled internal logging and the following is what I get:

2017-11-28 11:26:45.8063 Trace Executing Text: INSERT INTO [tblException] (DbVersionID, ExceptionDateTime, Message) SELECT MAX(DbVersionID), GETDATE(), @Message FROM tblDbVersion
2017-11-28 11:26:45.8063 Trace   Parameter: '@message' = 'Test Error Message' (String)
2017-11-28 11:26:45.8063 Error Error when writing to database. Exception: System.Data.SqlServerCe.SqlCeException (0x80004005): A parameter is not allowed in this location. Ensure that the '@' sign is in a valid location or that parameters are valid at all in this SQL statement.
   at System.Data.SqlServerCe.SqlCeCommand.ProcessResults(Int32 hr)
   at System.Data.SqlServerCe.SqlCeCommand.CompileQueryPlan()
   at System.Data.SqlServerCe.SqlCeCommand.ExecuteCommand(CommandBehavior behavior, String method, ResultSetOptions options)
   at System.Data.SqlServerCe.SqlCeCommand.ExecuteNonQuery()
   at NLog.Targets.DatabaseTarget.WriteEventToDatabase(LogEventInfo logEvent)
   at NLog.Targets.DatabaseTarget.Write(LogEventInfo logEvent)

It appears that the parameter isn't getting replaced in the query before it's being run. I tried adding single quotes in the command text just in case that would help but it just resulted in the literal string '@message' being inserted into the database field.

I can't see anything that I've done differently to the examples, so any help would be appreciated.

Regards,

Alex

Answer 1

As per the comment from @pmcilreavy

Have you tried temporarily removing the MAX and replacing with a literal and changing to INSERT INTO .. (blah) VALUES (blah, @Message); SqlCe has quite a few limitations and quirks compared to Sql Server so might be worth simplifying things where possible.

The issue appears to be that SQLCE doesn't support parameters in the select part of a select statement.