TraceFilter::ShouldTrace Method

When overridden in a derived class, determines whether the trace listener should trace the event.

Namespace:  System.Diagnostics
Assembly:  System (in System.dll)

public:
virtual bool ShouldTrace(
	TraceEventCache^ cache, 
	String^ source, 
	TraceEventType eventType, 
	int id, 
	String^ formatOrMessage, 
	array<Object^>^ args, 
	Object^ data1, 
	array<Object^>^ data
) abstract

Parameters

cache
Type: System.Diagnostics::TraceEventCache

The TraceEventCache that contains information for the trace event.

source
Type: System::String

The name of the source.

eventType
Type: System.Diagnostics::TraceEventType

One of the TraceEventType values specifying the type of event that has caused the trace.

id
Type: System::Int32

A trace identifier number.

formatOrMessage
Type: System::String

Either the format to use for writing an array of arguments specified by the args parameter, or a message to write.

args
Type: array<System::Object>

An array of argument objects.

data1
Type: System::Object

A trace data object.

data
Type: array<System::Object>

An array of trace data objects.

Return Value

Type: System::Boolean
true to trace the specified event; otherwise, false.

Notes to Inheritors

Implementations of this method should return true if the event specified by the passed parameters should be traced. Otherwise the method should return false. For example, a filter that allows only error events to pass through to the listener should inspect the eventType parameter and return true if the trace event type level is set to TraceEventType::Error or greater; otherwise, it should return false.

Implementations of the method should be prepared to handle nullptr in the following parameters: args, data1, data, formatOrMessage, and cache. If the parameter value is nullptr, the parameter is not part of the event. For example, if the args parameter is nullptr, it means that the event does not have any arguments. If the data parameter is nullptr, then there are either one or no data objects. If there is one data object, it will be found in the data1 parameter. The reason for the distinction between a single data object and an array of data objects is for performance. There is no reason to create an object array if only one object is traced, as is normally the case. If the data parameter is not nullptr, the data1 parameter must also not be nullptr.

It is guaranteed that the source parameter is not nullptr and not an empty string ("").

Implementations of the method can optionally throw the following exceptions:

The following code example shows how to override the ShouldTrace method to indicate tracing should occur when the trace event type of the event is equal to TraceEventType::Error.

public ref class ErrorFilter : TraceFilter
{
public:
    virtual bool ShouldTrace(TraceEventCache^ cache, String^ source,
        TraceEventType eventType, int id, String^ formatOrMessage,
        array<Object^>^ args, Object^ data, array<Object^>^ dataArray) override
    {
        return eventType == TraceEventType::Error;
    }
};

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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