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DefaultTraceListener.Fail Method (String)

Emits or displays a message and a stack trace for an assertion that always fails.

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

public override void Fail(
	string message


Type: System.String
The message to emit or display.

By default, this method sends the message parameter and a stack trace to a message box (when the application runs in user-interface mode) and to the DefaultTraceListener instance.

The following code example writes an error message to a DefaultTraceListener using the Fail(String) method. The method also writes the message to the console if a user interface is not available.

// Report that the required argument is not present.
const string ENTER_PARAM = "Enter the number of " +
          "possibilities as a command line argument.";
if (!defaultListener.AssertUiEnabled)

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.