TraceListener.GetSupportedAttributes Method

Definition

Gets the custom attributes supported by the trace listener.

protected public:
 virtual cli::array <System::String ^> ^ GetSupportedAttributes();
protected internal virtual string[] GetSupportedAttributes ();
abstract member GetSupportedAttributes : unit -> string[]
override this.GetSupportedAttributes : unit -> string[]
Protected Friend Overridable Function GetSupportedAttributes () As String()

Returns

String[]

A string array naming the custom attributes supported by the trace listener, or null if there are no custom attributes.

Examples

The following code sample shows an override of the GetSupportedAttributes method for a custom trace listener.

// This code example uses the following application configuration file:

//<?xml version="1.0" encoding="utf-8"?>
//      <source name="TraceTest" switchName="SourceSwitch" switchType="System.Diagnostics.SourceSwitch" >
//          <add name="Testlistener" />
//      <add name="SourceSwitch" value="Warning" />
//      <add name="Testlistener" type="CustomTraceListener.TestListener, CustomTraceListener, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" initializeData="TestListener" Source="test"/>
//    <trace autoflush="true" indentsize="4" />

using System;
using System.Diagnostics;
using System.Configuration;
using System.Reflection;
using System.Collections;
namespace CustomTraceListener
{
    class Program
    {
        static void Main(string[] args)
        {
            TraceSource ts = new TraceSource("TraceTest");
            Console.WriteLine(ts.Switch.DisplayName);
            foreach (TraceListener traceListener in ts.Listeners)
            {
                Console.Write("TraceListener: " + traceListener.Name + "\t");
                // The following output can be used to update the configuration file.
                Console.WriteLine("AssemblyQualifiedName = " +
                    (traceListener.GetType().AssemblyQualifiedName));
            }
            ts.TraceEvent(TraceEventType.Error, 1, "test error message");
        }
    }
    public class TestListener : TraceListener
    {
        string source;
        string name;
        public TestListener(string listenerName)
        {
            name = listenerName;
        }

        public string Source
        {
            get
            {
                foreach (DictionaryEntry de in this.Attributes)
                    if (de.Key.ToString().ToLower() == "source")
                        source = de.Value.ToString();
                return source;
            }
            set { source = value; }
        }

        public override void Write(string s)
        {
            Console.Write(name + " " + Source + ": " + s);
        }
        public override void WriteLine(string s)
        {
            Console.WriteLine(s);
        }
        protected override string[] GetSupportedAttributes()
        {
            return new string[] { "Source" };
        }

    }
}
// This code example creates the following output:
/*
SourceSwitch
TraceListener: Default  AssemblyQualifiedName = System.Diagnostics.DefaultTraceL
istener, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e0
89
TraceListener: Testlistener     AssemblyQualifiedName = CustomTraceListener.Test
Listener, CustomTraceListener, Version=1.0.0.0, Culture=neutral, PublicKeyToken=
null
TestListener test: TraceTest Error: 1 : test error message
*/
' This code example uses the following application configuration file:
'<?xml version="1.0" encoding="utf-8"?>
'      <source name="TraceTest" switchName="SourceSwitch" switchType="System.Diagnostics.SourceSwitch" >
'          <add name="Testlistener" />
'      <add name="SourceSwitch" value="Warning" />
'      <add name="Testlistener" type="CustomTraceListener.TestListener, CustomTraceListener, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" initializeData="TestListener" Source="test"/>
'    <trace autoflush="true" indentsize="4" />
Imports System.Diagnostics
Imports System.Configuration
Imports System.Reflection
Imports System.Collections

Namespace CustomTraceListener

    Class Program

        Shared Sub Main(ByVal args() As String)
            Dim ts As New TraceSource("TraceTest")
            Console.WriteLine(ts.Switch.DisplayName)
            Dim traceListener As TraceListener
            For Each traceListener In ts.Listeners
                Console.Write("TraceListener: " + traceListener.Name + vbTab)
                ' The following output can be used to update the configuration file.
                Console.WriteLine("AssemblyQualifiedName = " + traceListener.GetType().AssemblyQualifiedName)
            Next traceListener
            ts.TraceEvent(TraceEventType.Error, 1, "test error message")

        End Sub
    End Class

    Public Class TestListener
        Inherits TraceListener
        Private [m_source] As String
        Private m_name As String

        Public Sub New(ByVal listenerName As String)
            m_name = listenerName
        End Sub


        Public Property [Source]() As String
            Get
                Dim de As DictionaryEntry
                For Each de In Me.Attributes
                    If de.Key.ToString().ToLower() = "source" Then
                        [Source] = de.Value.ToString()
                    End If
                Next de
                Return [m_source]
            End Get
            Set(ByVal value As String)
                [m_source] = value
            End Set
        End Property

        Public Overrides Sub Write(ByVal s As String)
            Console.Write(m_name + " " + [Source] + ": " + s)

        End Sub

        Public Overrides Sub WriteLine(ByVal s As String)
            Console.WriteLine(s)

        End Sub

        Protected Overrides Function GetSupportedAttributes() As String()
            Return New String() {"Source"}

        End Function 'GetSupportedAttributes
    End Class
End Namespace 'CustomTraceListener
' This code example creates the following output:
'
'SourceSwitch
'TraceListener: Default  AssemblyQualifiedName = System.Diagnostics.DefaultTraceL
'istener, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e0
'89
'TraceListener: Testlistener     AssemblyQualifiedName = CustomTraceListener.Test
'Listener, CustomTraceListener, Version=1.0.0.0, Culture=neutral, PublicKeyToken=
'null
'TestListener test: TraceTest Error: 1 : test error message
'

Remarks

The default implementation for GetSupportedAttributes returns null.

Notes to Inheritors

When inheriting from the TraceListener class or a derived class, you can override the GetSupportedAttributes() method to provide custom attributes for your class.

Applies to