Index: /Include/Classes/System/Diagnostics/TraceListener.ab
===================================================================
--- /Include/Classes/System/Diagnostics/TraceListener.ab	(revision 289)
+++ /Include/Classes/System/Diagnostics/TraceListener.ab	(revision 290)
@@ -67,4 +67,26 @@
 			End Sub
 
+			' 条件をもとに文字列を出力
+			Sub WriteIf( condition As Boolean, value As Object )
+				If condition Then
+					Write( value )
+				End If
+			End Sub
+			Sub WriteIf( condition As Boolean, message As String )
+				If condition Then
+					Write( message )
+				End If
+			End Sub
+			Sub WriteIf( condition As Boolean, value As Object, category As String )
+				If condition Then
+					Write( value, category )
+				End If
+			End Sub
+			Sub WriteIf( condition As Boolean, message As String, category As String )
+				If condition Then
+					Write( message, category )
+				End If
+			End Sub
+
 
 			'----------------------------------------------------------------