[PreviewPane] Enable analyzer and fix warnings (#16995)

src/modules/previewpane/UnitTests-PreviewHandlerCommon/WebBrowserExtUnitTests.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Reflection;
+using Common;
 using Microsoft.PowerToys.STATestExtension;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using PreviewHandlerCommon;

src/modules/previewpane/common/PreviewHandlerCommon.csproj

@@ -18,6 +18,8 @@
     <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
     <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
     <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
+    <EnableNETAnalyzers>true</EnableNETAnalyzers>
+    <AnalysisMode>Recommended</AnalysisMode>
   </PropertyGroup>
   
   <PropertyGroup>

src/modules/previewpane/common/Utilities/ReadonlyStream.cs

@@ -107,7 +107,7 @@ namespace Common.Utilities
 
             if (buffer == null)
             {
-                throw new NullReferenceException("buffer is null");
+                throw new ArgumentNullException(nameof(buffer), "buffer is null");
             }
 
             if (offset < 0 || count < 0 || (offset + count) > buffer.Length)

src/modules/previewpane/common/controls/WebBrowserDownloadControlFlags.cs

@@ -4,6 +4,8 @@
 
 using System;
 
+namespace Common
+{
     /// <summary>
     /// Flags to control download and execution in Web Browser Control.
     /// Values of flags are defined in mshtmdid.h in distributed Windows Sdk.
@@ -107,3 +109,4 @@ public enum WebBrowserDownloadControlFlags : int
         /// </summary>
         SILENT = 0x40000000,
     }
+}

src/modules/previewpane/common/controls/WebBrowserExt.cs

@@ -6,6 +6,7 @@ using System;
 using System.Globalization;
 using System.Reflection;
 using System.Windows.Forms;
+using Common;
 
 namespace PreviewHandlerCommon
 {
@@ -52,7 +53,7 @@ namespace PreviewHandlerCommon
             {
                 object result;
 
-                if (name != null && name.Equals(DISPIDAMBIENTDLCONTROL, StringComparison.CurrentCulture))
+                if (name != null && name.Equals(DISPIDAMBIENTDLCONTROL, StringComparison.Ordinal))
                 {
                     // Using InvariantCulture since this is used for web browser configurations
                     result = Convert.ToInt32(