Add some nullable reference type annotations

src/NPoco.SqlServer/DatabaseTypes/SqlServer2012DatabaseType.cs

@@ -21,10 +21,10 @@ public override string BuildPageQuery(long skip, long take, PagingHelper.SQLPart
             return sqlPage;
         }
 
-        public override string GetAutoIncrementExpression(TableInfo ti)
+        public override string? GetAutoIncrementExpression(TableInfo ti)
         {
             if (!string.IsNullOrEmpty(ti.SequenceName))
-                return string.Format("NEXT VALUE FOR {0}", ti.SequenceName);
+                return $"NEXT VALUE FOR {ti.SequenceName}";
 
             return null;
         }

src/NPoco.SqlServer/DatabaseTypes/SqlServerDatabaseType.cs

@@ -74,7 +74,7 @@ public override IsolationLevel GetDefaultTransactionIsolationLevel()
             return base.LookupDbType(type, name);
         }
 
-        public override void InsertBulk<T>(IDatabase db, IEnumerable<T> pocos, InsertBulkOptions options)
+        public override void InsertBulk<T>(IDatabase db, IEnumerable<T> pocos, InsertBulkOptions? options)
         {
             SqlBulkCopyHelper.BulkInsert(db, pocos, options);
         }

src/NPoco.SqlServer/NPoco.SqlServer.csproj

@@ -10,6 +10,7 @@
 	<PackageTags>orm;sql;micro-orm;database;mvc</PackageTags>
 	<PackageProjectUrl>https://github.com/schotime/NPoco</PackageProjectUrl>
     <LangVersion>8.0</LangVersion>
+	<nullable>enable</nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/NPoco.SqlServer/SqlBulkCopyHelper.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Data;
 using System.Data.Common;
+using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Data.SqlClient;
@@ -13,12 +14,12 @@ public class SqlBulkCopyHelper
         public static Func<DbConnection, SqlConnection> SqlConnectionResolver = dbConn => (SqlConnection)dbConn;
         public static Func<DbTransaction, SqlTransaction> SqlTransactionResolver = dbTran => (SqlTransaction)dbTran;
 
-        public static void BulkInsert<T>(IDatabase db, IEnumerable<T> list, InsertBulkOptions insertBulkOptions)
+        public static void BulkInsert<T>(IDatabase db, IEnumerable<T> list, InsertBulkOptions? insertBulkOptions)
         {
             BulkInsert(db, list, SqlBulkCopyOptions.Default, insertBulkOptions);
         }
 
-        public static void BulkInsert<T>(IDatabase db, IEnumerable<T> list, SqlBulkCopyOptions sqlBulkCopyOptions, InsertBulkOptions insertBulkOptions)
+        public static void BulkInsert<T>(IDatabase db, IEnumerable<T> list, SqlBulkCopyOptions sqlBulkCopyOptions, InsertBulkOptions? insertBulkOptions)
         {
             using (var bulkCopy = new SqlBulkCopy(SqlConnectionResolver(db.Connection), sqlBulkCopyOptions, SqlTransactionResolver(db.Transaction)))
             {
@@ -42,7 +43,7 @@ public static async Task BulkInsertAsync<T>(IDatabase db, IEnumerable<T> list, S
         }
 
 
-        private static DataTable BuildBulkInsertDataTable<T>(IDatabase db, IEnumerable<T> list, SqlBulkCopy bulkCopy, SqlBulkCopyOptions sqlBulkCopyOptions, InsertBulkOptions insertBulkOptions)
+        private static DataTable BuildBulkInsertDataTable<T>(IDatabase db, IEnumerable<T> list, SqlBulkCopy bulkCopy, SqlBulkCopyOptions sqlBulkCopyOptions, InsertBulkOptions? insertBulkOptions)
         {
             var pocoData = db.PocoDataFactory.ForType(typeof (T));
 
@@ -78,7 +79,7 @@ private static DataTable BuildBulkInsertDataTable<T>(IDatabase db, IEnumerable<T
                 var values = new object[cols.Count];
                 for (var i = 0; i < values.Length; i++)
                 {
-                    var value = cols[i].Value.GetValue(item);
+                    var value = cols[i].Value.GetValue(item!);
                     if (db.Mappers != null)
                     {
                         value = db.Mappers.FindAndExecute(x => x.GetToDbConverter(cols[i].Value.ColumnType, cols[i].Value.MemberInfoData.MemberInfo), value);

src/NPoco.SqlServer/SqlServerDatabase.cs

@@ -8,14 +8,14 @@ namespace NPoco.SqlServer
 {
     public class SqlServerDatabase : Database
     {
-        private readonly IPollyPolicy _pollyPolicy;
+        private readonly IPollyPolicy? _pollyPolicy;
 
-        public SqlServerDatabase(string connectionString, IPollyPolicy pollyPolicy = null) 
+        public SqlServerDatabase(string connectionString, IPollyPolicy? pollyPolicy = null) 
             : this(connectionString, Singleton<SqlServer2012DatabaseType>.Instance, pollyPolicy)
         {
         }
 
-        public SqlServerDatabase(string connectionString, SqlServerDatabaseType databaseType, IPollyPolicy pollyPolicy) 
+        public SqlServerDatabase(string connectionString, SqlServerDatabaseType databaseType, IPollyPolicy? pollyPolicy) 
             : base(connectionString, databaseType, SqlClientFactory.Instance)
         {
             _pollyPolicy = pollyPolicy;

src/NPoco/IDatabase.cs

+#nullable enable
 using System;
 using System.Collections.Generic;
 using System.Linq.Expressions;
@@ -26,12 +27,12 @@ public interface IDatabase : IAsyncDatabase, IDatabaseQuery, IDatabaseConfig
         /// <summary>
         /// Insert POCO's into database using SqlBulkCopy for SqlServer (other DB's currently fall back to looping each row)
         /// </summary>        
-        void InsertBulk<T>(IEnumerable<T> pocos, InsertBulkOptions options = null);
+        void InsertBulk<T>(IEnumerable<T> pocos, InsertBulkOptions? options = null);
 
         /// <summary>
         /// Insert POCO's into database by concatenating sql using the provided batch options
         /// </summary>        
-        int InsertBatch<T>(IEnumerable<T> pocos, BatchOptions options = null);
+        int InsertBatch<T>(IEnumerable<T> pocos, BatchOptions? options = null);
 
         /// <summary>
         /// Update POCO in the specified table, primary key and primarkey value
@@ -46,12 +47,12 @@ public interface IDatabase : IAsyncDatabase, IDatabaseQuery, IDatabaseConfig
         /// <summary>
         /// Update POCO in the specified table, primary key, primarkey value for only the columns specified
         /// </summary>        
-        int Update(string tableName, string primaryKeyName, object poco, object primaryKeyValue, IEnumerable<string> columns);
+        int Update(string tableName, string primaryKeyName, object poco, object? primaryKeyValue, IEnumerable<string>? columns);
 
         /// <summary>
         /// Update POCO in the specified table, primary key for only the columns specified
         /// </summary>        
-        int Update(string tableName, string primaryKeyName, object poco, IEnumerable<string> columns);
+        int Update(string tableName, string primaryKeyName, object poco, IEnumerable<string>? columns);
 
         /// <summary>
         /// Update POCO by convention or configuration for only the columns specified
@@ -61,7 +62,7 @@ public interface IDatabase : IAsyncDatabase, IDatabaseQuery, IDatabaseConfig
         /// <summary>
         /// Update POCO by primary key for only the columns specified
         /// </summary>        
-        int Update(object poco, object primaryKeyValue, IEnumerable<string> columns);
+        int Update(object poco, object primaryKeyValue, IEnumerable<string>? columns);
 
         /// <summary>
         /// Update POCO by convention or configuration
@@ -97,7 +98,7 @@ public interface IDatabase : IAsyncDatabase, IDatabaseQuery, IDatabaseConfig
         /// <summary>
         /// Update POCO's into database by concatenating sql using the provided batch options
         /// </summary>     
-        int UpdateBatch<T>(IEnumerable<UpdateBatch<T>> pocos, BatchOptions options = null);
+        int UpdateBatch<T>(IEnumerable<UpdateBatch<T>> pocos, BatchOptions? options = null);
 
         /// <summary>
         /// Generate an update statement using a Fluent syntax. Remember to call Execute.
@@ -112,7 +113,7 @@ public interface IDatabase : IAsyncDatabase, IDatabaseQuery, IDatabaseConfig
         /// <summary>
         /// Delete POCO specifying the table name, primary key name and primary key value
         /// </summary>        
-        int Delete(string tableName, string primaryKeyName, object poco, object primaryKeyValue);
+        int Delete(string tableName, string primaryKeyName, object? poco, object? primaryKeyValue);
 
         /// <summary>
         /// Delete POCO using convention or configuration