完成延时加载开发与测试，ICollection集合待支持

FreeSql.Tests/MySql/Curd/MySqlSelectTest.cs

@@ -10,28 +10,39 @@ namespace FreeSql.Tests.MySql {
 		ISelect<Topic> select => g.mysql.Select<Topic>();
 
 		[Table(Name = "tb_topic")]
-		class Topic {
+		public class Topic {
 			[Column(IsIdentity = true, IsPrimary = true)]
 			public int Id { get; set; }
 			public int Clicks { get; set; }
 			public int TestTypeInfoGuid { get; set; }
-			public TestTypeInfo Type { get; set; }
+
+			public int TypeGuid { get; set; }
+			public virtual TestTypeInfo Type { get; set; }
 			public string Title { get; set; }
 			public DateTime CreateTime { get; set; }
 		}
-		class TestTypeInfo {
+		public class TestTypeInfo {
+			[Column(IsIdentity = true)]
 			public int Guid { get; set; }
 			public int ParentId { get; set; }
 			public TestTypeParentInfo Parent { get; set; }
 			public string Name { get; set; }
 		}
-		class TestTypeParentInfo {
+		public class TestTypeParentInfo {
+			[Column(IsIdentity = true)]
 			public int Id { get; set; }
 			public string Name { get; set; }
 
 			public List<TestTypeInfo> Types { get; set; }
 		}
 
+		[Fact]
+		public void Lazy() {
+			Topic t = g.mysql.Select<Topic>(2).ToOne();
+			Topic tz = g.mysql.Select<Topic>(2).ToOne();
+			var tzType = tz.Type;
+		}
+
 		[Fact]
 		public void ToList() {
 			var t0 = select.Limit(50).ToList();

FreeSql.Tests/g.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Text;
 
 
@@ -11,7 +12,7 @@ public class g {
 
 		.UseMonitorCommand(
 			cmd => {
-				Console.WriteLine(cmd.CommandText);
+				Trace.WriteLine(cmd.CommandText);
 			}, //监听SQL命令对象，在执行前
 			(cmd, traceLog) => {
 				Console.WriteLine(traceLog);

FreeSql/FreeSqlBuilder.cs

@@ -14,6 +14,7 @@ namespace FreeSql {
 		string[] _slaveConnectionString;
 		bool _isAutoSyncStructure = false;
 		bool _isSyncStructureToLower = false;
+		bool _isLazyLoading = false;
 		Action<DbCommand> _aopCommandExecuting = null;
 		Action<DbCommand, string> _aopCommandExecuted = null;
 
@@ -75,6 +76,15 @@ namespace FreeSql {
 			return this;
 		}
 		/// <summary>
+		/// 延时加载导航属性对象，导航属性需要声明 virtual
+		/// </summary>
+		/// <param name="value"></param>
+		/// <returns></returns>
+		public FreeSqlBuilder UseLazyLoading(bool value) {
+			_isLazyLoading = value;
+			return this;
+		}
+		/// <summary>
 		/// 监视数据库命令对象
 		/// </summary>
 		/// <param name="executing">执行前</param>
@@ -98,6 +108,7 @@ namespace FreeSql {
 			if (ret != null) {
 				ret.CodeFirst.IsAutoSyncStructure = _isAutoSyncStructure;
 				ret.CodeFirst.IsSyncStructureToLower = _isSyncStructureToLower;
+				ret.CodeFirst.IsLazyLoading = _isLazyLoading;
 				var ado = ret.Ado as Internal.CommonProvider.AdoProvider;
 				ado.AopCommandExecuting += _aopCommandExecuting;
 				ado.AopCommandExecuted += _aopCommandExecuted;

FreeSql/Generator/TemplateEngin.cs

@@ -544,8 +544,7 @@ return rTn;");
 			var type = assemly.DefinedTypes.Where(a => a.FullName.EndsWith(typename)).FirstOrDefault();
 			return Activator.CreateInstance(type) as ITemplateOutput;
 		}
-		static ConcurrentDictionary<string, (DateTime, object)> _compiler_objs = new ConcurrentDictionary<string, (DateTime, object)>();
-		static Lazy<CSScriptLib.RoslynEvaluator> _compiler = new Lazy<CSScriptLib.RoslynEvaluator>(() => {
+		internal static Lazy<CSScriptLib.RoslynEvaluator> _compiler = new Lazy<CSScriptLib.RoslynEvaluator>(() => {
 			var dlls = Directory.GetFiles(Directory.GetParent(Type.GetType("IFreeSql, FreeSql").Assembly.Location).FullName, "*.dll");
 			var compiler = new CSScriptLib.RoslynEvaluator();
 			compiler.DisableReferencingFromCode = false;

FreeSql/Interface/ICodeFirst.cs

@@ -12,6 +12,10 @@ namespace FreeSql {
 		/// 转小写同步结构
 		/// </summary>
 		bool IsSyncStructureToLower { get; set; }
+		/// <summary>
+		/// 延时加载导航属性对象，导航属性需要声明 virtual
+		/// </summary>
+		bool IsLazyLoading { get; set; }
 
 		/// <summary>
 		/// 将实体类型与数据库对比，返回DDL语句

FreeSql/Internal/CommonProvider/SelectProvider/Select0Provider.cs

@@ -249,9 +249,10 @@ namespace FreeSql.Internal.CommonProvider {
 			public Func<DbDataReader, T1> Read { get; set; }
 		}
 		protected GetAllFieldExpressionTreeInfo GetAllFieldExpressionTree() {
-			var key = string.Join("+", _tables.Select(a => $"{a.Table.DbName}-{a.Alias}"));
-			return _dicGetAllFieldExpressionTree.GetOrAdd(key, s => {
-				var type = _tables.First().Table.Type;
+			return _dicGetAllFieldExpressionTree.GetOrAdd(string.Join("+", _tables.Select(a => $"{a.Table.DbName}-{a.Alias}")), s => {
+				var tb1 = _tables.First().Table;
+				var type = tb1.TypeLazy ?? tb1.Type;
+				var props = tb1.Properties;
 
 				var rowExp = Expression.Parameter(typeof(DbDataReader), "row");
 				var returnTarget = Expression.Label(type);
@@ -266,14 +267,14 @@ namespace FreeSql.Internal.CommonProvider {
 					Expression.Assign(retExp, Expression.New(ctor, ctor.GetParameters().Select(a => Expression.Default(a.ParameterType)))),
 					Expression.Assign(dataIndexExp, Expression.Constant(0))
 				});
+				//typeof(Topic).GetMethod("get_Type").IsVirtual
 
 				var field = new StringBuilder();
 				var dicfield = new Dictionary<string, bool>();
 				var tb = _tables.First();
 				var index = 0;
 				var otherindex = 0;
-				var ps = _tables.First().Table.Properties;
-				foreach (var prop in ps.Values) {
+				foreach (var prop in props.Values) {
 					if (tb.Table.ColumnsByCs.TryGetValue(prop.Name, out var col)) { //普通字段
 						if (index > 0) field.Append(", ");
 						var quoteName = _commonUtils.QuoteSqlName(col.Attribute.Name);
@@ -283,7 +284,7 @@ namespace FreeSql.Internal.CommonProvider {
 						else dicfield.Add(quoteName, true);
 					} else {
 						var tb2 = _tables.Where(a => a.Table.Type == prop.PropertyType && a.Alias.Contains(prop.Name)).FirstOrDefault();
-						if (tb2 == null && ps.Where(pw => pw.Value.PropertyType == prop.PropertyType).Count() == 1) tb2 = _tables.Where(a => a.Table.Type == prop.PropertyType).FirstOrDefault();
+						if (tb2 == null && props.Where(pw => pw.Value.PropertyType == prop.PropertyType).Count() == 1) tb2 = _tables.Where(a => a.Table.Type == prop.PropertyType).FirstOrDefault();
 						if (tb2 == null) continue;
 						foreach (var col2 in tb2.Table.Columns.Values) {
 							if (index > 0) field.Append(", ");
@@ -333,6 +334,7 @@ namespace FreeSql.Internal.CommonProvider {
 						Expression.Assign(retExp, Expression.Convert(readExpValue, type))
 					});
 				}
+				if (tb1.TypeLazy != null) blockExp.Add(Expression.Call(retExp, tb1.TypeLazySetOrm, Expression.Constant(_orm))); //将 orm 传递给 lazy
 				blockExp.AddRange(new Expression[] {
 					Expression.Return(returnTarget, retExp),
 					Expression.Label(returnTarget, Expression.Default(type))
@@ -344,7 +346,8 @@ namespace FreeSql.Internal.CommonProvider {
 			});
 		}
 		protected (ReadAnonymousTypeInfo map, string field) GetAllFieldReflection() {
-			var type = _tables.First().Table.Type;
+			var tb1 = _tables.First().Table;
+			var type = tb1.Type;
 			var constructor = _dicConstructor.GetOrAdd(type, s => type.GetConstructor(new Type[0]));
 			var map = new ReadAnonymousTypeInfo { Consturctor = constructor, ConsturctorType = ReadAnonymousTypeInfoConsturctorType.Properties };
 
@@ -352,7 +355,7 @@ namespace FreeSql.Internal.CommonProvider {
 			var dicfield = new Dictionary<string, bool>();
 			var tb = _tables.First();
 			var index = 0;
-			var ps = _tables.First().Table.Properties;
+			var ps = tb1.Properties;
 			foreach (var p in ps.Values) {
 				var child = new ReadAnonymousTypeInfo { Property = p, CsName = p.Name };
 				if (tb.Table.ColumnsByCs.TryGetValue(p.Name, out var col)) { //普通字段

FreeSql/Internal/CommonUtils.cs

@@ -22,9 +22,14 @@ namespace FreeSql.Internal {
 		internal abstract string QuoteReadColumn(Type type, string columnName);
 		internal abstract string DbName { get; }
 
-		internal ICodeFirst CodeFirst { get; set; }
+		internal IFreeSql _orm { get; set; }
+		internal ICodeFirst CodeFirst => _orm.CodeFirst;
 		internal TableInfo GetTableByEntity(Type entity) => Utils.GetTableByEntity(entity, this);
 
+		public CommonUtils(IFreeSql orm) {
+			_orm = orm;
+		}
+
 		internal string WhereObject(TableInfo table, string aliasAndDot, object dywhere) {
 			if (dywhere == null) return "";
 			var type = dywhere.GetType();

FreeSql/Internal/Model/TableInfo.cs

@@ -5,6 +5,8 @@ using System.Reflection;
 namespace FreeSql.Internal.Model {
 	class TableInfo {
 		public Type Type { get; set; }
+		public Type TypeLazy { get; set; }
+		public MethodInfo TypeLazySetOrm { get; set; }
 		public Dictionary<string, PropertyInfo> Properties { get; set; } = new Dictionary<string, PropertyInfo>(StringComparer.CurrentCultureIgnoreCase);
 		public Dictionary<string, ColumnInfo> Columns { get; set; } = new Dictionary<string, ColumnInfo>(StringComparer.CurrentCultureIgnoreCase);
 		public Dictionary<string, ColumnInfo> ColumnsByCs { get; set; } = new Dictionary<string, ColumnInfo>(StringComparer.CurrentCultureIgnoreCase);

FreeSql/Internal/UtilsExpressionTree.cs

@@ -10,21 +10,23 @@ using System.Collections.Generic;
 using System.Data;
 using System.Data.Common;
 using System.Diagnostics;
+using System.IO;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Net;
 using System.Net.NetworkInformation;
 using System.Reflection;
+using System.Text;
 using System.Text.RegularExpressions;
 using System.Threading;
 
 namespace FreeSql.Internal {
 	class Utils {
 
-		static ConcurrentDictionary<string, TableInfo> _cacheGetTableByEntity = new ConcurrentDictionary<string, TableInfo>();
+		static ConcurrentDictionary<string, ConcurrentDictionary<Type, TableInfo>> _cacheGetTableByEntity = new ConcurrentDictionary<string, ConcurrentDictionary<Type, TableInfo>>();
 		internal static TableInfo GetTableByEntity(Type entity, CommonUtils common) {
 			if (entity.FullName.StartsWith("<>f__AnonymousType")) return null;
-			return _cacheGetTableByEntity.GetOrAdd($"{common.DbName}-{entity.FullName}", key => { //区分数据库类型缓存
+			return _cacheGetTableByEntity.GetOrAdd(common.DbName, k1 => new ConcurrentDictionary<Type, TableInfo>()).GetOrAdd(entity, k2 => { //区分数据库类型缓存
 				if (common.CodeFirst.GetDbInfo(entity) != null) return null;
 				
 				var tbattr = entity.GetCustomAttributes(typeof(TableAttribute), false).LastOrDefault() as TableAttribute;
@@ -39,11 +41,20 @@ namespace FreeSql.Internal {
 					trytb.DbOldName = trytb.DbOldName?.ToLower();
 				}
 				trytb.SelectFilter = tbattr?.SelectFilter;
+				var virtualProps = new List<(PropertyInfo, bool, bool)>();
 				foreach (var p in trytb.Properties.Values) {
 					var tp = common.CodeFirst.GetDbInfo(p.PropertyType);
 					//if (tp == null) continue;
 					var colattr = p.GetCustomAttributes(typeof(ColumnAttribute), false).LastOrDefault() as ColumnAttribute;
-					if (tp == null && colattr == null) continue;
+					if (tp == null && colattr == null) {
+						if (common.CodeFirst.IsLazyLoading) {
+							var getIsVirtual = trytb.Type.GetMethod($"get_{p.Name}")?.IsVirtual;
+							var setIsVirtual = trytb.Type.GetMethod($"set_{p.Name}")?.IsVirtual;
+							if (getIsVirtual == true || setIsVirtual == true)
+								virtualProps.Add((p, getIsVirtual == true, setIsVirtual == true));
+						}
+						continue;
+					}
 					if (colattr == null)
 						colattr = new ColumnAttribute {
 							Name = p.Name,
@@ -93,7 +104,66 @@ namespace FreeSql.Internal {
 					foreach (var col in trytb.Primarys)
 						col.Attribute.IsPrimary = true;
 				}
-				_cacheGetTableByEntity.TryAdd(entity.FullName, trytb);
+
+				if (common.CodeFirst.IsLazyLoading && virtualProps.Any()) {
+					//virtual 属性延时加载，生态产生新的重写类
+					if (trytb.Type.IsNotPublic) throw new Exception("【延时加载】功能发生错误，实体类必须声明为 public");
+
+					var overrieds = 0;
+					var cscode = new StringBuilder();
+					cscode.AppendLine("using System;")
+						.AppendLine("using FreeSql.DataAnnotations;")
+						.AppendLine("using System.Collections.Generic;")
+						.AppendLine("using System.Linq;")
+						.AppendLine("")
+						.Append("public class FreeSqlOverrideLazyEntity").Append(trytb.Type.Name).Append(" : ").Append(trytb.Type.FullName.Replace("+", ".")).AppendLine(" {")
+						.AppendLine("	public IFreeSql __fsql_orm__ { get; set; }\r\n");
+					foreach(var vp in virtualProps) {
+						TableInfo pktb = null;
+						if (vp.Item1.PropertyType == trytb.Type) pktb = trytb;
+						else pktb = GetTableByEntity(vp.Item1.PropertyType, common);
+						if (pktb == null || pktb.Primarys.Any() == false) {
+							//continue;
+							throw new Exception($"【延时加载】功能发生错误，导航属性 {trytb.Type.FullName}.{vp.Item1.Name} 类型不正确，或者实体类型 {vp.Item1.PropertyType.FullName} 缺少主键标识");
+						}
+
+						var lmbdWhere = new StringBuilder();
+						var vpcols = new ColumnInfo[pktb.Primarys.Length];
+						for (var a = 0; a < pktb.Primarys.Length; a++) {
+							if (trytb.ColumnsByCs.TryGetValue($"{vp.Item1.Name}{pktb.Primarys[a].CsName}", out var trycol) == false && //骆峰命名
+								trytb.ColumnsByCs.TryGetValue($"{vp.Item1.Name}_{pktb.Primarys[a].CsName}", out trycol) == false //下划线命名
+								) {
+								pktb = null;
+								throw new Exception($"【延时加载】功能发生错误，导航属性 {trytb.Type.FullName}.{vp.Item1.Name} 没有找到对应的字段 {vp.Item1.Name}{pktb.Primarys[a].CsName} 或 {vp.Item1.Name}_{pktb.Primarys[a].CsName}");
+								//break;
+							}
+							if (a > 0) lmbdWhere.Append(" && ");
+							lmbdWhere.Append("a.").Append(pktb.Primarys[a].CsName).Append(" == this.").Append(trycol.CsName);
+						}
+						if (pktb == null) continue;
+
+						cscode.Append("	public override ").Append(vp.Item1.PropertyType.FullName.Replace("+", ".")).Append(" ").Append(vp.Item1.Name).AppendLine(" {");
+						if (vp.Item2) { //get 重写
+							cscode.Append("		get => base.").Append(vp.Item1.Name)
+								.Append(" ?? (base.").Append(vp.Item1.Name)
+								.Append(" = __fsql_orm__.Select<").Append(vp.Item1.PropertyType.FullName.Replace("+", ".")).Append(">().Where(a => ")
+								.Append(lmbdWhere.ToString())
+								.Append(").ToOne()").AppendLine(");");
+						}
+						if (vp.Item3) { //set 重写
+							cscode.Append("		set => base.").Append(vp.Item1.Name).AppendLine(" = value;");
+						}
+						cscode.AppendLine("	}");
+						++overrieds;
+					}
+					if (overrieds > 0) {
+						cscode.AppendLine("}");
+						var assemly = Generator.TemplateEngin._compiler.Value.CompileCode(cscode.ToString());
+						var type = assemly.DefinedTypes.Where(a => a.FullName.EndsWith($"FreeSqlOverrideLazyEntity{trytb.Type.Name}")).FirstOrDefault();
+						trytb.TypeLazy = type;
+						trytb.TypeLazySetOrm = type.GetProperty("__fsql_orm__").GetSetMethod();
+					}
+				}
 				return trytb;
 			});
 		}

FreeSql/MySql/MySqlCodeFirst.cs

@@ -24,6 +24,7 @@ namespace FreeSql.MySql {
 
 		public bool IsAutoSyncStructure { get; set; } = true;
 		public bool IsSyncStructureToLower { get; set; } = false;
+		public bool IsLazyLoading { get; set; } = false;
 
 		static object _dicCsToDbLock = new object();
 		static Dictionary<string, (MySqlDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)> _dicCsToDb = new Dictionary<string, (MySqlDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)>() {

FreeSql/MySql/MySqlProvider.cs

@@ -36,7 +36,7 @@ namespace FreeSql.MySql {
 			this.Ado = new MySqlAdo(this.InternalCommonUtils, this.Cache, log, masterConnectionString, slaveConnectionString);
 
 			this.DbFirst = new MySqlDbFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
-			this.InternalCommonUtils.CodeFirst = this.CodeFirst = new MySqlCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
+			this.CodeFirst = new MySqlCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
 		}
 
 		internal CommonUtils InternalCommonUtils { get; }

FreeSql/MySql/MySqlUtils.cs

@@ -8,10 +8,7 @@ using System.Data.Common;
 namespace FreeSql.MySql {
 
 	class MySqlUtils : CommonUtils {
-		IFreeSql _orm;
-
-		public MySqlUtils(IFreeSql orm) {
-			_orm = orm;
+		public MySqlUtils(IFreeSql orm) : base(orm) {
 		}
 
 		internal override DbParameter AppendParamter(List<DbParameter> _params, string parameterName, Type type, object value) {

FreeSql/Oracle/OracleCodeFirst.cs

@@ -24,6 +24,7 @@ namespace FreeSql.Oracle {
 
 		public bool IsAutoSyncStructure { get; set; } = true;
 		public bool IsSyncStructureToLower { get; set; } = false;
+		public bool IsLazyLoading { get; set; } = false;
 
 		static object _dicCsToDbLock = new object();
 		static Dictionary<string, (OracleDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)> _dicCsToDb = new Dictionary<string, (OracleDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)>() {

FreeSql/Oracle/OracleProvider.cs

@@ -35,7 +35,7 @@ namespace FreeSql.Oracle {
 			this.Cache = new CacheProvider(cache, log);
 			this.Ado = new OracleAdo(this.InternalCommonUtils, this.Cache, log, masterConnectionString, slaveConnectionString);
 
-			this.InternalCommonUtils.CodeFirst = this.CodeFirst = new OracleCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
+			this.CodeFirst = new OracleCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
 		}
 
 		internal CommonUtils InternalCommonUtils { get; }

FreeSql/Oracle/OracleUtils.cs

@@ -8,9 +8,7 @@ using System.Data.Common;
 namespace FreeSql.Oracle {
 
 	class OracleUtils : CommonUtils {
-		IFreeSql _orm;
-		public OracleUtils(IFreeSql orm) {
-			_orm = orm;
+		public OracleUtils(IFreeSql orm) : base(orm) {
 		}
 
 		internal override DbParameter AppendParamter(List<DbParameter> _params, string parameterName, Type type, object value) {

FreeSql/PostgreSQL/PostgreSQLCodeFirst.cs

@@ -29,6 +29,7 @@ namespace FreeSql.PostgreSQL {
 
 		public bool IsAutoSyncStructure { get; set; } = true;
 		public bool IsSyncStructureToLower { get; set; } = false;
+		public bool IsLazyLoading { get; set; } = false;
 
 		static object _dicCsToDbLock = new object();
 		static Dictionary<string, (NpgsqlDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)> _dicCsToDb = new Dictionary<string, (NpgsqlDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)>() {

FreeSql/PostgreSQL/PostgreSQLProvider.cs

@@ -36,7 +36,7 @@ namespace FreeSql.PostgreSQL {
 			this.Ado = new PostgreSQLAdo(this.InternalCommonUtils, this.Cache, log, masterConnectionString, slaveConnectionString);
 
 			this.DbFirst = new PostgreSQLDbFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
-			this.InternalCommonUtils.CodeFirst = this.CodeFirst = new PostgreSQLCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
+			this.CodeFirst = new PostgreSQLCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
 		}
 
 		internal CommonUtils InternalCommonUtils { get; }

FreeSql/PostgreSQL/PostgreSQLUtils.cs

@@ -11,9 +11,7 @@ using System.Net;
 namespace FreeSql.PostgreSQL {
 
 	class PostgreSQLUtils : CommonUtils {
-		IFreeSql _orm;
-		public PostgreSQLUtils(IFreeSql orm) {
-			_orm = orm;
+		public PostgreSQLUtils(IFreeSql orm) : base(orm) {
 		}
 
 		static Array getParamterArrayValue(Type arrayType, object value, object defaultValue) {

FreeSql/SqlServer/SqlServerCodeFirst.cs

@@ -23,6 +23,7 @@ namespace FreeSql.SqlServer {
 
 		public bool IsAutoSyncStructure { get; set; } = true;
 		public bool IsSyncStructureToLower { get; set; } = false;
+		public bool IsLazyLoading { get; set; } = false;
 
 		static object _dicCsToDbLock = new object();
 		static Dictionary<string, (SqlDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)> _dicCsToDb = new Dictionary<string, (SqlDbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)>() {

FreeSql/SqlServer/SqlServerProvider.cs

@@ -35,7 +35,7 @@ namespace FreeSql.SqlServer {
 			this.Ado = new SqlServerAdo(this.InternalCommonUtils, this.Cache, log, masterConnectionString, slaveConnectionString);
 
 			this.DbFirst = new SqlServerDbFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
-			this.InternalCommonUtils.CodeFirst = this.CodeFirst = new SqlServerCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
+			this.CodeFirst = new SqlServerCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
 		}
 
 		internal CommonUtils InternalCommonUtils { get; }

FreeSql/SqlServer/SqlServerUtils.cs

@@ -8,9 +8,7 @@ using System.Data.SqlClient;
 namespace FreeSql.SqlServer {
 
 	class SqlServerUtils : CommonUtils {
-		IFreeSql _orm;
-		public SqlServerUtils(IFreeSql orm) {
-			_orm = orm;
+		public SqlServerUtils(IFreeSql orm) : base(orm) {
 		}
 
 		internal override DbParameter AppendParamter(List<DbParameter> _params, string parameterName, Type type, object value) {

FreeSql/Sqlite/SqliteCodeFirst.cs

@@ -23,6 +23,7 @@ namespace FreeSql.Sqlite {
 
 		public bool IsAutoSyncStructure { get; set; } = true;
 		public bool IsSyncStructureToLower { get; set; } = false;
+		public bool IsLazyLoading { get; set; } = false;
 
 		static object _dicCsToDbLock = new object();
 		static Dictionary<string, (DbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)> _dicCsToDb = new Dictionary<string, (DbType type, string dbtype, string dbtypeFull, bool? isUnsigned, bool? isnullable, object defaultValue)>() {

FreeSql/Sqlite/SqliteProvider.cs

@@ -35,7 +35,7 @@ namespace FreeSql.Sqlite {
 			this.Cache = new CacheProvider(cache, log);
 			this.Ado = new SqliteAdo(this.InternalCommonUtils, this.Cache, log, masterConnectionString, slaveConnectionString);
 
-			this.InternalCommonUtils.CodeFirst = this.CodeFirst = new SqliteCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
+			this.CodeFirst = new SqliteCodeFirst(this, this.InternalCommonUtils, this.InternalCommonExpression);
 		}
 
 		internal CommonUtils InternalCommonUtils { get; }

FreeSql/Sqlite/SqliteUtils.cs

@@ -9,9 +9,7 @@ using System.Data.SQLite;
 namespace FreeSql.Sqlite {
 
 	class SqliteUtils : CommonUtils {
-		IFreeSql _orm;
-		public SqliteUtils(IFreeSql orm) {
-			_orm = orm;
+		public SqliteUtils(IFreeSql orm) : base(orm) {
 		}
 
 		internal override DbParameter AppendParamter(List<DbParameter> _params, string parameterName, Type type, object value) {

readme.md

@@ -31,6 +31,8 @@ IFreeSql fsql = new FreeSql.FreeSqlBuilder()
 
     .UseAutoSyncStructure(true) //自动同步实体结构到数据库
     .UseSyncStructureToLower(true) //转小写同步结构
+
+	.UseLazyLoading(true) //延时加载导航属性对象，导航属性需要声明 virtual
     .Build();
 ```