From 01fa69d714d177d11d45db76c33bc3cae7451333 Mon Sep 17 00:00:00 2001
From: Dave Glick <dave@daveaglick.com>
Date: Sat, 7 Nov 2015 20:29:45 -0500
Subject: [PATCH] LoggerConfiguration.CreateLogger() now throws if called more
 than once, resolves #561

---
 src/Serilog/LoggerConfiguration.cs             | 5 +++++
 test/Serilog.Tests/LoggerConfigurationTests.cs | 8 ++++++++
 2 files changed, 13 insertions(+)

diff --git a/src/Serilog/LoggerConfiguration.cs b/src/Serilog/LoggerConfiguration.cs
index 0f662e80a..a8795eb26 100644
--- a/src/Serilog/LoggerConfiguration.cs
+++ b/src/Serilog/LoggerConfiguration.cs
@@ -38,6 +38,7 @@ public class LoggerConfiguration
         LogEventLevel _minimumLevel = LogEventLevel.Information;
         LoggingLevelSwitch _levelSwitch;
         int _maximumDestructuringDepth = 10;
+        bool _loggerCreated;
 
         /// <summary>
         /// Configures the sinks that log events will be emitted to.
@@ -124,6 +125,10 @@ public LoggerSettingsConfiguration ReadFrom
         /// disposed.</remarks>
         public ILogger CreateLogger()
         {
+            if (_loggerCreated)
+                throw new InvalidOperationException($"CreateLogger was previously called and can only be called once.");
+            _loggerCreated = true;
+
             if (!_logEventSinks.Any())
                 return new SilentLogger();
 
diff --git a/test/Serilog.Tests/LoggerConfigurationTests.cs b/test/Serilog.Tests/LoggerConfigurationTests.cs
index 1178436da..92ba973fb 100644
--- a/test/Serilog.Tests/LoggerConfigurationTests.cs
+++ b/test/Serilog.Tests/LoggerConfigurationTests.cs
@@ -25,6 +25,14 @@ public void Dispose()
             }
         }
 
+        [Test]
+        public void CreateLoggerThrowsIfCalledMoreThanOnce()
+        {
+            var loggerConfiguration = new LoggerConfiguration();
+            loggerConfiguration.CreateLogger();
+            Assert.Throws<InvalidOperationException>(() => loggerConfiguration.CreateLogger());
+        }
+
         [Test]
         public void DisposableSinksAreDisposedAlongWithRootLogger()
         {