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WhenLayoutRendererWrapper.cs
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WhenLayoutRendererWrapper.cs
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//
// Copyright (c) 2004-2019 Jaroslaw Kowalski <jaak@jkowalski.net>, Kim Christensen, Julian Verdurmen
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// * Neither the name of Jaroslaw Kowalski nor the names of its
// contributors may be used to endorse or promote products derived from this
// software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
//
namespace NLog.LayoutRenderers.Wrappers
{
using System;
using System.Text;
using NLog.Conditions;
using NLog.Config;
using NLog.Layouts;
using NLog.Internal;
/// <summary>
/// Only outputs the inner layout when the specified condition has been met.
/// </summary>
[LayoutRenderer("when")]
[AmbientProperty("When")]
[ThreadAgnostic]
[ThreadSafe]
public sealed class WhenLayoutRendererWrapper : WrapperLayoutRendererBuilderBase, IRawValue
{
/// <summary>
/// Gets or sets the condition that must be met for the <see cref="WrapperLayoutRendererBase.Inner"/> layout to be printed.
/// </summary>
/// <docgen category="Transformation Options" order="10"/>
[RequiredParameter]
public ConditionExpression When { get; set; }
/// <summary>
/// If <see cref="When"/> is not met, print this layout.
/// </summary>
/// <docgen category="Transformation Options" order="10"/>
public Layout Else { get; set; }
/// <inheritdoc/>
protected override void Append(StringBuilder builder, LogEventInfo logEvent)
{
int orgLength = builder.Length;
try
{
if (ShouldRenderInner(logEvent))
{
Inner?.RenderAppendBuilder(logEvent, builder);
}
else
{
Else?.RenderAppendBuilder(logEvent, builder);
}
}
catch
{
builder.Length = orgLength; // Rewind/Truncate on exception
throw;
}
}
private bool ShouldRenderInner(LogEventInfo logEvent)
{
return When == null || true.Equals(When.Evaluate(logEvent));
}
/// <inheritdoc/>
[Obsolete("Inherit from WrapperLayoutRendererBase and override RenderInnerAndTransform() instead. Marked obsolete in NLog 4.6")]
protected override void TransformFormattedMesssage(StringBuilder target)
{
}
/// <inheritdoc />
public bool TryGetRawValue(LogEventInfo logEvent, out object value)
{
if (ShouldRenderInner(logEvent))
{
return TryGetRawValueFromLayout(logEvent, Inner, out value);
}
return TryGetRawValueFromLayout(logEvent, Else, out value);
}
private static bool TryGetRawValueFromLayout(LogEventInfo logEvent, Layout layout, out object value)
{
if (layout == null)
{
value = null;
return false;
}
return layout.TryGetRawValue(logEvent, out value);
}
}
}