Refactor format provider handling in RichTextBoxSink options

Author: vonhoff

Serilog.Sinks.RichTextBox.WinForms.Colored/RichTextBoxSinkLoggerConfigurationExtensions.cs

@@ -23,6 +23,7 @@
 using Serilog.Sinks.RichTextBoxForms.Rendering;
 using Serilog.Sinks.RichTextBoxForms.Themes;
 using System;
+using System.Globalization;
 using System.Windows.Forms;
 
 namespace Serilog
@@ -58,8 +59,9 @@ public static LoggerConfiguration RichTextBox(
             LoggingLevelSwitch? levelSwitch = null)
         {
             var appliedTheme = theme ?? ThemePresets.Literate;
-            var renderer = new TemplateRenderer(appliedTheme, outputTemplate, formatProvider);
-            var options = new RichTextBoxSinkOptions(appliedTheme, autoScroll, maxLogLines, outputTemplate, formatProvider);
+            var appliedFormatProvider = formatProvider ?? CultureInfo.InvariantCulture;
+            var renderer = new TemplateRenderer(appliedTheme, outputTemplate, appliedFormatProvider);
+            var options = new RichTextBoxSinkOptions(appliedTheme, autoScroll, maxLogLines, outputTemplate, appliedFormatProvider);
             richTextBoxSink = new RichTextBoxSink(richTextBoxControl, options, renderer);
             return sinkConfiguration.Sink(richTextBoxSink, minimumLogEventLevel, levelSwitch);
         }

Serilog.Sinks.RichTextBox.WinForms.Colored/Sinks/RichTextBoxForms/RichTextBoxSinkOptions.cs

@@ -18,6 +18,7 @@
 
 using Serilog.Sinks.RichTextBoxForms.Themes;
 using System;
+using System.Globalization;
 
 namespace Serilog.Sinks.RichTextBoxForms
 {
@@ -46,7 +47,7 @@ public RichTextBoxSinkOptions(
             Theme = theme;
             MaxLogLines = maxLogLines;
             OutputTemplate = outputTemplate;
-            FormatProvider = formatProvider;
+            FormatProvider = formatProvider ?? CultureInfo.InvariantCulture;
         }
 
         public bool AutoScroll { get; set; }