- FreeSql.Repository 增加 filter 参数，现实数据过滤 + 验证；

如：var postRepos = fsql.GetGuidRepository<Post>(a => a.TopicId == 1); postRepos CURD 方法都会以 lambad 条件作为查询或验证，Update/Insert验证错误时会抛出异常。
- ISelect 增加 First/FirstAsync；

FreeSql/FreeSql.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
-    <Version>0.1.6</Version>
+    <Version>0.1.7</Version>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     <Authors>YeXiangQin</Authors>
     <Description>打造 .NETCore 最方便的 ORM，DbFirst 与 CodeFirst 混合使用，提供从实体同步数据库，或者从数据库生成实体代码，支持 MySql/SqlServer/PostgreSQL/Oracle/Sqlite 数据库。</Description>

FreeSql/Interface/Curd/ISelect/ISelect0.cs

@@ -28,6 +28,13 @@ namespace FreeSql {
 		T1 ToOne();
 		Task<T1> ToOneAsync();
 
+		/// <summary>
+		/// 执行SQL查询，返回 T1 实体所有字段的第一条记录，记录不存在时返回 null
+		/// </summary>
+		/// <returns></returns>
+		T1 First();
+		Task<T1> FirstAsync();
+
 		/// <summary>
 		/// 返回即将执行的SQL语句
 		/// </summary>

FreeSql/Internal/CommonExpression.cs

@@ -203,6 +203,7 @@ namespace FreeSql.Internal {
 		}
 
 		internal string ExpressionLambdaToSql(Expression exp, List<SelectTableInfo> _tables, List<SelectColumnInfo> _selectColumnMap, Func<Expression[], string> getSelectGroupingMapString, SelectTableInfoType tbtype, bool isQuoteName) {
+			if (exp == null) return "";
 			switch (exp.NodeType) {
 				case ExpressionType.Not: return $"not({ExpressionLambdaToSql((exp as UnaryExpression)?.Operand, _tables, _selectColumnMap, getSelectGroupingMapString, tbtype, isQuoteName)})";
 				case ExpressionType.Quote: return ExpressionLambdaToSql((exp as UnaryExpression)?.Operand, _tables, _selectColumnMap, getSelectGroupingMapString, tbtype, isQuoteName);

FreeSql/Internal/CommonProvider/SelectProvider/Select0Provider.cs

@@ -205,6 +205,9 @@ namespace FreeSql.Internal.CommonProvider {
 			return (await this.ToListAsync()).FirstOrDefault();
 		}
 
+		public T1 First() => this.ToOne();
+		public Task<T1> FirstAsync() => this.ToOneAsync();
+
 		protected List<TReturn> ToListMapReader<TReturn>((ReadAnonymousTypeInfo map, string field) af) {
 			var sql = this.ToSql(af.field);
 			if (_cache.seconds > 0 && string.IsNullOrEmpty(_cache.key)) _cache.key = $"{sql}{string.Join("|", _params.Select(a => a.Value))}";
@@ -461,7 +464,7 @@ namespace FreeSql.Internal.CommonProvider {
 			return (await this.ToListMapReaderAsync<TReturn>((map, field.Length > 0 ? field.Remove(0, 2).ToString() : null))).FirstOrDefault();
 		}
 
-		protected TSelect InternalWhere(Expression exp) => this.Where(_commonExpression.ExpressionWhereLambda(_tables, exp, null));
+		protected TSelect InternalWhere(Expression exp) => exp == null ? this as TSelect : this.Where(_commonExpression.ExpressionWhereLambda(_tables, exp, null));
 
 		protected TSelect InternalJoin(Expression exp) {
 			return this as TSelect;