Enable nullable annotations for the repo, then update a few files wit…

…h nullable, convert .NET 1 data structures to strongly typed collections, and perform other modernizations

src/Directory.Build.props

@@ -2,5 +2,6 @@
     <PropertyGroup>
         <UseSharedCompilation>true</UseSharedCompilation>
         <LangVersion>latest</LangVersion>
+        <Nullable>annotations</Nullable>
     </PropertyGroup>
 </Project>

src/log4net.Tests/Appender/AdoNet/Log4NetCommand.cs

@@ -22,84 +22,53 @@
 using System;
 using System.Data;
 
+#nullable enable
+
 namespace log4net.Tests.Appender.AdoNet
 {
   public class Log4NetCommand : IDbCommand
   {
-    #region AdoNetAppender
-
-    private static Log4NetCommand mostRecentInstance;
-
-    private IDbTransaction transaction;
-    private string commandText;
-    private readonly IDataParameterCollection parameters;
-    private CommandType commandType;
-    private int executeNonQueryCount;
-
     public Log4NetCommand()
     {
-      mostRecentInstance = this;
+      MostRecentInstance = this;
 
-      parameters = new Log4NetParameterCollection();
+      Parameters = new Log4NetParameterCollection();
     }
 
     public void Dispose()
     {
       // empty
     }
 
-    public IDbTransaction Transaction
-    {
-      get { return transaction; }
-      set { transaction = value; }
-    }
+    public IDbTransaction? Transaction { get; set; }
 
     public int ExecuteNonQuery()
     {
-      executeNonQueryCount++;
+      ExecuteNonQueryCount++;
       return 0;
     }
 
-    public int ExecuteNonQueryCount
-    {
-      get { return executeNonQueryCount; }
-    }
+    public int ExecuteNonQueryCount { get; private set; }
 
     public IDbDataParameter CreateParameter()
     {
       return new Log4NetParameter();
     }
 
-    public string CommandText
-    {
-      get { return commandText; }
-      set { commandText = value; }
-    }
+#pragma warning disable CS8766 // Nullability of reference types in return type doesn't match implicitly implemented member (possibly because of nullability attributes).
+    public string? CommandText { get; set; }
+#pragma warning restore CS8766
 
-    public CommandType CommandType
-    {
-      get { return commandType; }
-      set { commandType = value; }
-    }
+    public CommandType CommandType { get; set; }
 
     public void Prepare()
     {
       // empty
     }
 
-    public IDataParameterCollection Parameters
-    {
-      get { return parameters; }
-    }
+    public IDataParameterCollection Parameters { get; }
 
-    public static Log4NetCommand MostRecentInstance
-    {
-      get { return mostRecentInstance; }
-    }
-
-    #endregion
-
-    #region Not Implemented
+    public static Log4NetCommand? MostRecentInstance { get; private set; }
 
     public void Cancel()
     {
@@ -121,24 +90,22 @@ public object ExecuteScalar()
       throw new NotImplementedException();
     }
 
-    public IDbConnection Connection
+    public IDbConnection? Connection
     {
-      get { throw new NotImplementedException(); }
-      set { throw new NotImplementedException(); }
+      get => throw new NotImplementedException();
+      set => throw new NotImplementedException();
     }
 
     public int CommandTimeout
     {
-      get { throw new NotImplementedException(); }
-      set { throw new NotImplementedException(); }
+      get => throw new NotImplementedException();
+      set => throw new NotImplementedException();
     }
 
     public UpdateRowSource UpdatedRowSource
     {
-      get { throw new NotImplementedException(); }
-      set { throw new NotImplementedException(); }
+      get => throw new NotImplementedException();
+      set => throw new NotImplementedException();
     }
-
-    #endregion
   }
 }

src/log4net.Tests/Appender/AdoNet/Log4NetConnection.cs

@@ -22,40 +22,29 @@
 using System;
 using System.Data;
 
+#nullable enable
+
 namespace log4net.Tests.Appender.AdoNet
 {
   public class Log4NetConnection : IDbConnection
   {
-    #region AdoNetAppender
-
-    private static Log4NetConnection mostRecentInstance;
-
-    private bool open;
-    private string connectionString;
+    private bool _open;
 
     public Log4NetConnection()
     {
-      mostRecentInstance = this;
+      MostRecentInstance = this;
     }
 
     public void Close()
     {
-      open = false;
+      _open = false;
     }
 
-    public ConnectionState State
-    {
-      get
-      {
-        return open ? ConnectionState.Open : ConnectionState.Closed;
-      }
-    }
+    public ConnectionState State => _open ? ConnectionState.Open : ConnectionState.Closed;
 
-    public string ConnectionString
-    {
-      get { return connectionString; }
-      set { connectionString = value; }
-    }
+#pragma warning disable CS8766 // Nullability of reference types in return type doesn't match implicitly implemented member (possibly because of nullability attributes).
+    public string? ConnectionString { get; set; }
+#pragma warning restore CS8766
 
     public IDbTransaction BeginTransaction()
     {
@@ -69,17 +58,10 @@ public IDbCommand CreateCommand()
 
     public void Open()
     {
-      open = true;
-    }
-
-    public static Log4NetConnection MostRecentInstance
-    {
-      get { return mostRecentInstance; }
+      _open = true;
     }
 
-    #endregion
-
-    #region Not Implemented
+    public static Log4NetConnection? MostRecentInstance { get; private set; }
 
     public IDbTransaction BeginTransaction(IsolationLevel il)
     {
@@ -91,21 +73,13 @@ public void ChangeDatabase(string databaseName)
       throw new NotImplementedException();
     }
 
-    public int ConnectionTimeout
-    {
-      get { throw new NotImplementedException(); }
-    }
+    public int ConnectionTimeout => throw new NotImplementedException();
 
-    public string Database
-    {
-      get { throw new NotImplementedException(); }
-    }
+    public string Database => throw new NotImplementedException();
 
     public void Dispose()
     {
       throw new NotImplementedException();
     }
-
-    #endregion
   }
 }

src/log4net.Tests/Appender/AdoNet/Log4NetTransaction.cs

@@ -22,12 +22,12 @@
 using System;
 using System.Data;
 
+#nullable enable
+
 namespace log4net.Tests.Appender.AdoNet
 {
   public class Log4NetTransaction : IDbTransaction
   {
-    #region AdoNetAppender
-
     public void Commit()
     {
       // empty
@@ -38,25 +38,13 @@ public void Rollback()
       // empty
     }
 
-    #endregion
-
-    #region Not Implemented
+    public IDbConnection Connection => throw new NotImplementedException();
 
-    public IDbConnection Connection
-    {
-      get { throw new NotImplementedException(); }
-    }
-
-    public IsolationLevel IsolationLevel
-    {
-      get { throw new NotImplementedException(); }
-    }
+    public IsolationLevel IsolationLevel => throw new NotImplementedException();
 
     public void Dispose()
     {
       throw new NotImplementedException();
     }
-
-    #endregion
   }
 }

src/log4net.Tests/Appender/AdoNetAppenderTest.cs

@@ -41,9 +41,11 @@ public void NoBufferingTest()
     {
       ILoggerRepository rep = LogManager.CreateRepository(Guid.NewGuid().ToString());
 
-      AdoNetAppender adoNetAppender = new AdoNetAppender();
-      adoNetAppender.BufferSize = -1;
-      adoNetAppender.ConnectionType = typeof(Log4NetConnection).AssemblyQualifiedName;
+      AdoNetAppender adoNetAppender = new AdoNetAppender
+      {
+          BufferSize = -1,
+          ConnectionType = typeof(Log4NetConnection).AssemblyQualifiedName!
+      };
       adoNetAppender.ActivateOptions();
 
       BasicConfigurator.Configure(rep, adoNetAppender);
@@ -61,9 +63,11 @@ public void BufferingTest()
 
       int bufferSize = 5;
 
-      AdoNetAppender adoNetAppender = new AdoNetAppender();
-      adoNetAppender.BufferSize = bufferSize;
-      adoNetAppender.ConnectionType = typeof(Log4NetConnection).AssemblyQualifiedName;
+      AdoNetAppender adoNetAppender = new AdoNetAppender
+      {
+          BufferSize = bufferSize,
+          ConnectionType = typeof(Log4NetConnection).AssemblyQualifiedName!
+      };
       adoNetAppender.ActivateOptions();
 
       BasicConfigurator.Configure(rep, adoNetAppender);
@@ -83,7 +87,6 @@ public void BufferingTest()
     public void WebsiteExample()
     {
       XmlDocument log4netConfig = new XmlDocument();
-      #region Load log4netConfig
       log4netConfig.LoadXml(@"
                 <log4net>
                 <appender name=""AdoNetAppender"" type=""log4net.Appender.AdoNetAppender"">
@@ -140,7 +143,6 @@ public void WebsiteExample()
                     <appender-ref ref=""AdoNetAppender"" />
                   </root>  
                 </log4net>");
-      #endregion
 
       ILoggerRepository rep = LogManager.CreateRepository(Guid.NewGuid().ToString());
       XmlConfigurator.Configure(rep, log4netConfig["log4net"]);
@@ -173,7 +175,6 @@ public void WebsiteExample()
     public void BufferingWebsiteExample()
     {
       XmlDocument log4netConfig = new XmlDocument();
-      #region Load log4netConfig
       log4netConfig.LoadXml(@"
                 <log4net>
                 <appender name=""AdoNetAppender"" type=""log4net.Appender.AdoNetAppender"">
@@ -230,7 +231,6 @@ public void BufferingWebsiteExample()
                     <appender-ref ref=""AdoNetAppender"" />
                   </root>  
                 </log4net>");
-      #endregion
 
       ILoggerRepository rep = LogManager.CreateRepository(Guid.NewGuid().ToString());
       XmlConfigurator.Configure(rep, log4netConfig["log4net"]);
@@ -267,7 +267,6 @@ public void BufferingWebsiteExample()
     public void NullPropertyXmlConfig()
     {
       XmlDocument log4netConfig = new XmlDocument();
-      #region Load log4netConfig
       log4netConfig.LoadXml(@"
                 <log4net>
                 <appender name=""AdoNetAppender"" type=""log4net.Appender.AdoNetAppender"">
@@ -289,7 +288,6 @@ public void NullPropertyXmlConfig()
                     <appender-ref ref=""AdoNetAppender"" />
                   </root>  
                 </log4net>");
-      #endregion
 
       ILoggerRepository rep = LogManager.CreateRepository(Guid.NewGuid().ToString());
       XmlConfigurator.Configure(rep, log4netConfig["log4net"]);
@@ -305,7 +303,7 @@ public void NullPropertyXmlConfig()
     }
 
     [Test]
-    public void NullPropertyProgmaticConfig()
+    public void NullPropertyProgrammaticConfig()
     {
       AdoNetAppenderParameter productIdParam = new AdoNetAppenderParameter();
       productIdParam.ParameterName = "@productId";