TraceFilter Class

Represents the base class for filtering trace output. The TraceFilter class is an abstract class.

Namespace:

System.Diagnostics

Assembly:

System.dll

Inheritance Hierarchy:

System.Object
System.Diagnostics.TraceFilter

Derived Classes:

System.Diagnostics.EventTypeFilter
System.Diagnostics.PerformanceCounterPermissionFilter

Remarks

You can create custom trace filters by deriving from the TraceFilter class and implementing the ShouldTrace method. This method determines whether a trace event should be passed to a trace listener. The .NET Framework provides two built-in trace filters: EventTypeFilter and PerformanceCounterPermissionFilter.

Trace filters are associated with trace listeners. When a trace event is sent to a trace listener, the listener calls the filter's ShouldTrace method to determine if the event should be processed. This allows you to control the granularity of your trace output without modifying the trace source or the trace listener itself.

Methods

`ShouldTrace(TraceEventCache cache, string source, TraceEventType severity, object id, object data)`

Abstract. Determines whether the specified trace event should be traced.

Parameters:

cache: A TraceEventCache object that contains the current process, thread, and stack information.
source: The name of the trace source that generated the event.
severity: A TraceEventType value indicating the severity of the event.
id: The identifier of the trace event.
data: An object containing additional trace data.

Returns:

true if the trace event should be traced; otherwise, false.

Example

The following example shows how to create a custom trace filter that only traces TraceEventType.Error and TraceEventType.Critical events.

Custom Trace Filter Implementation

                        
using System;

namespace MyTracing

{

    public class ErrorOnlyTraceFilter : System.Diagnostics.TraceFilter

    {

        public override bool ShouldTrace(

            System.Diagnostics.TraceEventCache cache,

            string source,

            System.Diagnostics.TraceEventType severity,

            int id,

            object data)

        {

            return (severity == System.Diagnostics.TraceEventType.Error ||

                    severity == System.Diagnostics.TraceEventType.Critical);

        }

    }

}

Applying the Custom Filter

                        
using System;

using System.Diagnostics;

public class Program

{

    public static void Main(string[] args)

    {

        TraceSource ts = new TraceSource("MyApp");

        ConsoleTraceListener consoleListener = new ConsoleTraceListener();

        consoleListener.Filter = new MyTracing.ErrorOnlyTraceFilter();

        ts.Listeners.Clear();

        ts.Listeners.Add(consoleListener);

        ts.TraceInformation("This is an informational message."); // Will not be displayed

        ts.TraceWarning("This is a warning message."); // Will not be displayed

        ts.TraceError("This is an error message."); // Will be displayed

        ts.TraceCritical("This is a critical message."); // Will be displayed

        ts.Close();

    }

}