DefaultTraceListener Class

Definition

Namespace:

System.Diagnostics

Assembly:

System.Diagnostics.TraceSource.dll

Source:

DefaultTraceListener.cs

Provides the default output methods and behavior for tracing.

public ref class DefaultTraceListener : System::Diagnostics::TraceListener

public class DefaultTraceListener : System.Diagnostics.TraceListener

type DefaultTraceListener = class
    inherit TraceListener

Public Class DefaultTraceListener
Inherits TraceListener

Inheritance

Object

MarshalByRefObject

TraceListener

DefaultTraceListener

Examples

The following code example calculates binomial coefficients, which are values used in probability and statistics. This example uses a DefaultTraceListener to trace results and log errors. It creates a new DefaultTraceListener, adds it to the Trace.Listeners collection, and sets the LogFileName property to the log file specified in the command-line arguments.

If an error is detected while processing the input parameter, or if the CalcBinomial function throws an exception, the Fail method logs and displays an error message. If the AssertUiEnabled property is false, the error message is also written to the console. When the result is calculated successfully, the Write(String) and WriteLine(String) methods write the results to the log file.

The Fail, Write, and WriteLine methods cause trace information to be written only to the DefaultTraceListener. To write trace information to all listeners in the Trace.Listeners collection, use the Fail, Write, and WriteLine methods of the Trace class.

using System;
using System.Diagnostics;
using Microsoft.VisualBasic;

class Binomial
{

    // args(0) is the number of possibilities for binomial coefficients.
    // args(1) is the file specification for the trace log file.
    public static void Main(string[] args)
    {

        decimal possibilities;
        decimal iter;

        // Remove the original default trace listener.
        Trace.Listeners.RemoveAt(0);

        // Create and add a new default trace listener.
        DefaultTraceListener defaultListener;
        defaultListener = new DefaultTraceListener();
        Trace.Listeners.Add(defaultListener);

        // Assign the log file specification from the command line, if entered.
        if (args.Length>=2)
        {
            defaultListener.LogFileName = args[1];
        }

        // Validate the number of possibilities argument.
        if (args.Length>=1)

            // Verify that the argument is a number within the correct range.
        {
            try
            {
                const decimal MAX_POSSIBILITIES = 99;
                possibilities = Decimal.Parse(args[0]);
                if (possibilities<0||possibilities>MAX_POSSIBILITIES)
                {
                    throw new Exception(String.Format("The number of possibilities must " +
                        "be in the range 0..{0}.", MAX_POSSIBILITIES));
                }
            }
            catch(Exception ex)
            {
                string failMessage = String.Format("\"{0}\" " +
                    "is not a valid number of possibilities.", args[0]);
                defaultListener.Fail(failMessage, ex.Message);
                if (!defaultListener.AssertUiEnabled)
                {
                    Console.WriteLine(failMessage+ "\n" +ex.Message);
                }
                return;
            }
        }
        else
        {
            // Report that the required argument is not present.
            const string ENTER_PARAM = "Enter the number of " +
                      "possibilities as a command line argument.";
            defaultListener.Fail(ENTER_PARAM);
            if (!defaultListener.AssertUiEnabled)
            {
                Console.WriteLine(ENTER_PARAM);
            }
            return;
        }

        for(iter=0; iter<=possibilities; iter++)
        {
            decimal result;
            string binomial;

            // Compute the next binomial coefficient and handle all exceptions.
            try
            {
                result = CalcBinomial(possibilities, iter);
            }
            catch(Exception ex)
            {
                string failMessage = String.Format("An exception was raised when " +
                    "calculating Binomial( {0}, {1} ).", possibilities, iter);
                defaultListener.Fail(failMessage, ex.Message);
                if (!defaultListener.AssertUiEnabled)
                {
                    Console.WriteLine(failMessage+ "\n" +ex.Message);
                }
                return;
            }

            // Format the trace and console output.
            binomial = String.Format("Binomial( {0}, {1} ) = ", possibilities, iter);
            defaultListener.Write(binomial);
            defaultListener.WriteLine(result.ToString());
            Console.WriteLine("{0} {1}", binomial, result);
        }
    }

    public static decimal CalcBinomial(decimal possibilities, decimal outcomes)
    {

        // Calculate a binomial coefficient, and minimize the chance of overflow.
        decimal result = 1;
        decimal iter;
        for(iter=1; iter<=possibilities-outcomes; iter++)
        {
            result *= outcomes+iter;
            result /= iter;
        }
        return result;
    }
}

Imports System.Diagnostics

Module Binomial

    ' args(0) is the number of possibilities for binomial coefficients.
    ' args(1) is the file specification for the trace log file.
    Sub Main(ByVal args() As String)

        Dim possibilities As Decimal
        Dim iter As Decimal

        ' Remove the original default trace listener.
        Trace.Listeners.RemoveAt(0)

        ' Create and add a new default trace listener.
        Dim defaultListener As DefaultTraceListener
        defaultListener = New DefaultTraceListener
        Trace.Listeners.Add(defaultListener)

        ' Assign the log file specification from the command line, if entered.
        If args.Length >= 2 Then
            defaultListener.LogFileName = args(1)
        End If

        ' Validate the number of possibilities argument.
        If args.Length >= 1 Then

            ' Verify that the argument is a number within the correct range.
            Try
                Const MAX_POSSIBILITIES As Decimal = 99
                possibilities = Decimal.Parse(args(0))
                If possibilities < 0 Or possibilities > MAX_POSSIBILITIES Then
                    Throw New Exception( _
                        String.Format("The number of possibilities must " & _
                            "be in the range 0..{0}.", MAX_POSSIBILITIES))
                End If
            Catch ex As Exception
                Dim failMessage As String = String.Format("""{0}"" " & _
                    "is not a valid number of possibilities.", args(0))
                defaultListener.Fail(failMessage, ex.Message)
                If Not defaultListener.AssertUiEnabled Then
                    Console.WriteLine(failMessage & vbCrLf & ex.Message)
                End If
                Return
            End Try
        Else
            ' Report that the required argument is not present.
            Const ENTER_PARAM As String = "Enter the number of " & _
                "possibilities as a command line argument."
            defaultListener.Fail(ENTER_PARAM)
            If Not defaultListener.AssertUiEnabled Then
                Console.WriteLine(ENTER_PARAM)
            End If
            Return
        End If

        For iter = 0 To possibilities
            Dim result As Decimal
            Dim binomial As String

            ' Compute the next binomial coefficient and handle all exceptions.
            Try
                result = CalcBinomial(possibilities, iter)
            Catch ex As Exception
                Dim failMessage As String = String.Format( _
                        "An exception was raised when " & _
                        "calculating Binomial( {0}, {1} ).", _
                        possibilities, iter)
                defaultListener.Fail(failmessage, ex.Message)
                If Not defaultListener.AssertUiEnabled Then
                    Console.WriteLine(failMessage & vbCrLf & ex.Message)
                End If
                Return
            End Try

            ' Format the trace and console output.
            binomial = String.Format("Binomial( {0}, {1} ) = ", _
                            possibilities, iter)
            defaultListener.Write(binomial)
            defaultListener.WriteLine(result.ToString)
            Console.WriteLine("{0} {1}", binomial, result)
        Next
    End Sub

    Function CalcBinomial(ByVal possibilities As Decimal, _
                        ByVal outcomes As Decimal) As Decimal

        ' Calculate a binomial coefficient, and minimize the chance of overflow.
        Dim result As Decimal = 1
        Dim iter As Decimal
        For iter = 1 To possibilities - outcomes
            result *= outcomes + iter
            result /= iter
        Next
        Return result
    End Function
End Module

Remarks

An instance of this class is automatically added to the Debug.Listeners and Trace.Listeners collections. Explicitly adding a second DefaultTraceListener causes duplicate messages in the debugger output window and duplicate message boxes for asserts.

By default, the Write and WriteLine methods emit the message to the Win32 OutputDebugString function and to the Debugger.Log method.

The Fail method, by default, displays a message box when the application is running in a user interface mode; it also emits the message using WriteLine.

Note

The display of the message box for Assert and Fail method calls depends on the presence of the DefaultTraceListener. If the DefaultTraceListener is not in the Listeners collection, the message box is not displayed. The DefaultTraceListener can be removed by calling the Clear method on the Listeners property (System.Diagnostics.Trace.Listeners.Clear()). For .NET Framework apps, you can also use the <clear> element and the <remove> element in your app's configuration file.

You must enable tracing or debugging to use a trace listener. The following syntax is compiler specific. If you use compilers other than C# or Visual Basic, refer to the documentation for your compiler.

• To enable debugging in C#, add the /d:DEBUG flag to the compiler command line when you compile your code, or add #define DEBUG to the top of your file. In Visual Basic, add the /d:DEBUG=True flag to the compiler command line.

• To enable tracing in C#, add the /d:TRACE flag to the compiler command line when you compile your code, or add #define TRACE to the top of your file. In Visual Basic, add the /d:TRACE=True flag to the compiler command line.

For .NET Framework apps, you can add a trace listener by editing the configuration file that corresponds to the name of your application. Within this file, you can add a listener, set its type and set its parameters, remove a listener, or clear all the listeners previously set by the application. The configuration file should be formatted similar to the following example:

<configuration>  
<system.diagnostics>  
  <trace autoflush="false" indentsize="4">  
    <listeners>  
      <remove name="Default" />  
      <add name="myListener" type="System.Diagnostics.TextWriterTraceListener" initializeData="c:\myListener.log" />  
    </listeners>  
  </trace>  
</system.diagnostics>  
</configuration>  

Constructors

DefaultTraceListener()

Initializes a new instance of the DefaultTraceListener class with "Default" as its Name property value.

Properties

AssertUiEnabled	Gets or sets a value indicating whether the application is running in user-interface mode.
Attributes	Gets the custom trace listener attributes defined in the application configuration file. (Inherited from TraceListener)
Filter	Gets or sets the trace filter for the trace listener. (Inherited from TraceListener)
IndentLevel	Gets or sets the indent level. (Inherited from TraceListener)
IndentSize	Gets or sets the number of spaces in an indent. (Inherited from TraceListener)
IsThreadSafe	Gets a value indicating whether the trace listener is thread safe. (Inherited from TraceListener)
LogFileName	Gets or sets the name of a log file to write trace or debug messages to.
Name	Gets or sets a name for this TraceListener. (Inherited from TraceListener)
NeedIndent	Gets or sets a value indicating whether to indent the output. (Inherited from TraceListener)
TraceOutputOptions	Gets or sets the trace output options. (Inherited from TraceListener)

Methods

Close()	When overridden in a derived class, closes the output stream so it no longer receives tracing or debugging output. (Inherited from TraceListener)
CreateObjRef(Type)	Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject)
Dispose()	Releases all resources used by the TraceListener. (Inherited from TraceListener)
Dispose(Boolean)	Releases the unmanaged resources used by the TraceListener and optionally releases the managed resources. (Inherited from TraceListener)
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
Fail(String, String)	Emits or displays detailed messages and a stack trace for an assertion that always fails.
Fail(String)	Emits or displays a message and a stack trace for an assertion that always fails.
Flush()	When overridden in a derived class, flushes the output buffer. (Inherited from TraceListener)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetLifetimeService()	Obsolete. Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject)
GetSupportedAttributes()	Gets the custom attributes supported by the trace listener. (Inherited from TraceListener)
GetType()	Gets the Type of the current instance. (Inherited from Object)
InitializeLifetimeService()	Obsolete. Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
MemberwiseClone(Boolean)	Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject)
ToString()	Returns a string that represents the current object. (Inherited from Object)
TraceData(TraceEventCache, String, TraceEventType, Int32, Object)	Writes trace information, a data object and event information to the listener specific output. (Inherited from TraceListener)
TraceData(TraceEventCache, String, TraceEventType, Int32, Object[])	Writes trace information, an array of data objects and event information to the listener specific output. (Inherited from TraceListener)
TraceEvent(TraceEventCache, String, TraceEventType, Int32, String, Object[])	Writes trace information, a formatted array of objects and event information to the listener specific output. (Inherited from TraceListener)
TraceEvent(TraceEventCache, String, TraceEventType, Int32, String)	Writes trace information, a message, and event information to the listener specific output. (Inherited from TraceListener)
TraceEvent(TraceEventCache, String, TraceEventType, Int32)	Writes trace and event information to the listener specific output. (Inherited from TraceListener)
TraceTransfer(TraceEventCache, String, Int32, String, Guid)	Writes trace information, a message, a related activity identity and event information to the listener specific output. (Inherited from TraceListener)
Write(Object, String)	Writes a category name and the value of the object's ToString() method to the listener you create when you implement the TraceListener class. (Inherited from TraceListener)
Write(Object)	Writes the value of the object's ToString() method to the listener you create when you implement the TraceListener class. (Inherited from TraceListener)
Write(String, String)	Writes a category name and a message to the listener you create when you implement the TraceListener class. (Inherited from TraceListener)
Write(String)	Writes the output to the OutputDebugString function and to the Log(Int32, String, String) method.
WriteIndent()	Writes the indent to the listener you create when you implement this class, and resets the NeedIndent property to false. (Inherited from TraceListener)
WriteLine(Object, String)	Writes a category name and the value of the object's ToString() method to the listener you create when you implement the TraceListener class, followed by a line terminator. (Inherited from TraceListener)
WriteLine(Object)	Writes the value of the object's ToString() method to the listener you create when you implement the TraceListener class, followed by a line terminator. (Inherited from TraceListener)
WriteLine(String, String)	Writes a category name and a message to the listener you create when you implement the TraceListener class, followed by a line terminator. (Inherited from TraceListener)
WriteLine(String)	Writes the output to the OutputDebugString function and to the Log(Int32, String, String) method, followed by a carriage return and line feed (\r\n).

Thread Safety

This class is thread safe.

See also

• TraceListener
• TextWriterTraceListener
• ConsoleTraceListener
• Debug
• Trace