ILogger Interface
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
This interface defines a "logger" in the build system. A logger subscribes to build system events. All logger classes must implement this interface to be recognized by the build engine.
public interface class ILogger[System.Runtime.InteropServices.ComVisible(true)]
public interface ILogger[<System.Runtime.InteropServices.ComVisible(true)>]
type ILogger = interfacePublic Interface ILogger- Derived
- Attributes
Examples
The following example shows how to write a basic logger.
using System;
using System.IO;
using System.Security;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;
namespace MyLoggers
{
// This logger will derive from the Microsoft.Build.Utilities.Logger class,
// which provides it with getters and setters for Verbosity and Parameters,
// and a default empty Shutdown() implementation.
public class BasicFileLogger : Logger
{
/// <summary>
/// Initialize is guaranteed to be called by MSBuild at the start of the build
/// before any events are raised.
/// </summary>
public override void Initialize(IEventSource eventSource)
{
// The name of the log file should be passed as the first item in the
// "parameters" specification in the /logger switch. It is required
// to pass a log file to this logger. Other loggers may have zero or more than
// one parameters.
if (null == Parameters)
{
throw new LoggerException("Log file was not set.");
}
string[] parameters = Parameters.Split(';');
string logFile = parameters[0];
if (String.IsNullOrEmpty(logFile))
{
throw new LoggerException("Log file was not set.");
}
if (parameters.Length > 1)
{
throw new LoggerException("Too many parameters passed.");
}
try
{
// Open the file
this.streamWriter = new StreamWriter(logFile);
}
catch (Exception ex)
{
if
(
ex is UnauthorizedAccessException
|| ex is ArgumentNullException
|| ex is PathTooLongException
|| ex is DirectoryNotFoundException
|| ex is NotSupportedException
|| ex is ArgumentException
|| ex is SecurityException
|| ex is IOException
)
{
throw new LoggerException("Failed to create log file: " + ex.Message);
}
else
{
// Unexpected failure
throw;
}
}
// For brevity, we'll only register for certain event types. Loggers can also
// register to handle TargetStarted/Finished and other events.
eventSource.ProjectStarted += new ProjectStartedEventHandler(eventSource_ProjectStarted);
eventSource.TaskStarted += new TaskStartedEventHandler(eventSource_TaskStarted);
eventSource.MessageRaised += new BuildMessageEventHandler(eventSource_MessageRaised);
eventSource.WarningRaised += new BuildWarningEventHandler(eventSource_WarningRaised);
eventSource.ErrorRaised += new BuildErrorEventHandler(eventSource_ErrorRaised);
eventSource.ProjectFinished += new ProjectFinishedEventHandler(eventSource_ProjectFinished);
}
void eventSource_ErrorRaised(object sender, BuildErrorEventArgs e)
{
// BuildErrorEventArgs adds LineNumber, ColumnNumber, File, amongst other parameters
string line = String.Format(": ERROR {0}({1},{2}): ", e.File, e.LineNumber, e.ColumnNumber);
WriteLineWithSenderAndMessage(line, e);
}
void eventSource_WarningRaised(object sender, BuildWarningEventArgs e)
{
// BuildWarningEventArgs adds LineNumber, ColumnNumber, File, amongst other parameters
string line = String.Format(": Warning {0}({1},{2}): ", e.File, e.LineNumber, e.ColumnNumber);
WriteLineWithSenderAndMessage(line, e);
}
void eventSource_MessageRaised(object sender, BuildMessageEventArgs e)
{
// BuildMessageEventArgs adds Importance to BuildEventArgs
// Let's take account of the verbosity setting we've been passed in deciding whether to log the message
if ((e.Importance == MessageImportance.High && IsVerbosityAtLeast(LoggerVerbosity.Minimal))
|| (e.Importance == MessageImportance.Normal && IsVerbosityAtLeast(LoggerVerbosity.Normal))
|| (e.Importance == MessageImportance.Low && IsVerbosityAtLeast(LoggerVerbosity.Detailed))
)
{
WriteLineWithSenderAndMessage(String.Empty, e);
}
}
void eventSource_TaskStarted(object sender, TaskStartedEventArgs e)
{
// TaskStartedEventArgs adds ProjectFile, TaskFile, TaskName
// To keep this log clean, this logger will ignore these events.
}
void eventSource_ProjectStarted(object sender, ProjectStartedEventArgs e)
{
// ProjectStartedEventArgs adds ProjectFile, TargetNames
// Just the regular message string is good enough here, so just display that.
WriteLine(String.Empty, e);
indent++;
}
void eventSource_ProjectFinished(object sender, ProjectFinishedEventArgs e)
{
// The regular message string is good enough here too.
indent--;
WriteLine(String.Empty, e);
}
/// <summary>
/// Write a line to the log, adding the SenderName and Message
/// (these parameters are on all MSBuild event argument objects)
/// </summary>
private void WriteLineWithSenderAndMessage(string line, BuildEventArgs e)
{
if (0 == String.Compare(e.SenderName, "MSBuild", true /*ignore case*/))
{
// Well, if the sender name is MSBuild, let's leave it out for prettiness
WriteLine(line, e);
}
else
{
WriteLine(e.SenderName + ": " + line, e);
}
}
/// <summary>
/// Just write a line to the log
/// </summary>
private void WriteLine(string line, BuildEventArgs e)
{
for (int i = indent; i > 0; i--)
{
streamWriter.Write("\t");
}
streamWriter.WriteLine(line + e.Message);
}
/// <summary>
/// Shutdown() is guaranteed to be called by MSBuild at the end of the build, after all
/// events have been raised.
/// </summary>
public override void Shutdown()
{
// Done logging, let go of the file
streamWriter.Close();
}
private StreamWriter streamWriter;
private int indent;
}
}
Remarks
All logger classes must implement this interface to be recognized by the MSBuild engine.
Instead of implementing this interface directly, you can also derive your class from the helper class, Logger, which provides default implementations of some ILogger members.
Properties
| Parameters |
This property holds the user-specified parameters to the logger. If parameters are not provided, a logger should revert to defaults. If a logger does not take parameters, it can ignore this property. |
| Verbosity |
The verbosity level directs the amount of detail that appears in a logger's event log. Though this is only a recommendation based on user preferences, and a logger is free to choose the exact events it logs, it is still important that the guidelines for each level be followed, for a good user experience. |
Methods
| Initialize(IEventSource) |
Called by the build engine to allow loggers to subscribe to the events they desire. |
| Shutdown() |
Called by the build engine to allow loggers to release any resources they may have allocated at initialization time, or during the build. |