EFCore扩展Update方法(实现 Update User SET Id=Id+1)

EFCore扩展Update方法(实现 Update User SET Id = Id + 1)

• 源码地址(github)

前言

1. EFCore在操作更新的时候往往需要先查询一遍数据，再去更新相应的字段，如果针对批量更新的话会很麻烦，效率也很低。
2. 目前github上 EFCore.Extentions 项目,实现批量更新挺方便的，但是针对 Update User SET Id = Id + 1 这种操作还是没有解决
3. 本文主要就是扩展自更新Update

实现原理

1. 先根据IQuaryable 获取到SQL语句

        private static readonly TypeInfo QueryCompilerTypeInfo = typeof(QueryCompiler).GetTypeInfo();
        private static readonly FieldInfo QueryCompilerField = typeof(EntityQueryProvider).GetTypeInfo().DeclaredFields.First(x => x.Name == "_queryCompiler");
        private static readonly FieldInfo QueryModelGeneratorField = QueryCompilerTypeInfo.DeclaredFields.First(x => x.Name == "_queryModelGenerator");
        private static readonly FieldInfo DataBaseField = QueryCompilerTypeInfo.DeclaredFields.Single(x => x.Name == "_database");
        private static readonly PropertyInfo DatabaseDependenciesField = typeof(Database).GetTypeInfo().DeclaredProperties.Single(x => x.Name == "Dependencies");

        /// <summary>
        /// 将query 转化为sql语句
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="query"></param>
        /// <returns></returns>
        internal static string ToSql<TEntity>(this IQueryable<TEntity> query) where TEntity : class
        {
            var queryCompiler = (QueryCompiler)QueryCompilerField.GetValue(query.Provider);
            var modelGenerator = (QueryModelGenerator)QueryModelGeneratorField.GetValue(queryCompiler);
            var queryModel = modelGenerator.ParseQuery(query.Expression);
            var database = (IDatabase)DataBaseField.GetValue(queryCompiler);
            var databaseDependencies = (DatabaseDependencies)DatabaseDependenciesField.GetValue(database);
            var queryCompilationContext = databaseDependencies.QueryCompilationContextFactory.Create(false);
            var modelVisitor = (RelationalQueryModelVisitor)queryCompilationContext.CreateQueryModelVisitor();

            modelVisitor.CreateQueryExecutor<TEntity>(queryModel);
            string sql = modelVisitor.Queries.First().ToString();
            return sql;
        }

2. 把获取的查询语句的，From之前的语句砍掉，然后拼接

        public static (string, string) GetBatchSql<T>(IQueryable<T> query) where T : class, new()
        {
            string sqlQuery = query.ToSql();
            string tableAlias = sqlQuery.Substring(8, sqlQuery.IndexOf("]") - 8);
            int indexFROM = sqlQuery.IndexOf(Environment.NewLine);
            string sql = sqlQuery.Substring(indexFROM, sqlQuery.Length - indexFROM);
            sql = sql.Contains("{") ? sql.Replace("{", "{{") : sql; // Curly brackets have to escaped:
            sql = sql.Contains("}") ? sql.Replace("}", "}}") : sql; // https://github.com/aspnet/EntityFrameworkCore/issues/8820
            return (sql, tableAlias);
        }

3. 根据传入的表达式Expression<Func<T,bool> 生成(Update [a] SET) 之后要更新的部分.列如：Expression<Func<T,bool> expression=a=>a.Id == a.Id + 1 生成[a].[Id]=[a].[Id]+parm_0 pram_0=1

通过分析Expression的节点[NodeType]来生成相应的操作符，递归拼接sql语句和参数

        public static void CreateUpdateBody(string Param, Expression expression, ref StringBuilder sb, ref List<SqlParameter> sp)
        {
            if (expression is BinaryExpression binaryExpression)
            {
                CreateUpdateBody(Param, binaryExpression.Left, ref sb, ref sp);

                switch (binaryExpression.NodeType)
                {
                    case ExpressionType.Add:
                        sb.Append(" +");
                        break;
                    case ExpressionType.Divide:
                        sb.Append(" /");
                        break;
                    case ExpressionType.Multiply:
                        sb.Append(" *");
                        break;
                    case ExpressionType.Subtract:
                        sb.Append(" -");
                        break;
                    case ExpressionType.And:
                        sb.Append(" ,");
                        break;
                    case ExpressionType.AndAlso:
                        sb.Append(" ,");
                        break;
                    case ExpressionType.Or:
                        sb.Append(" ,");
                        break;
                    case ExpressionType.OrElse:
                        sb.Append(" ,");
                        break;
                    case ExpressionType.Equal:
                        sb.Append(" =");
                        break;
                    default: break;
                }

                CreateUpdateBody(Param, binaryExpression.Right, ref sb, ref sp);
            }

            if (expression is ConstantExpression constantExpression)
            {
                var parmName = $"param_{sp.Count}";
                sp.Add(new SqlParameter(parmName, constantExpression.Value));
                sb.Append($" @{parmName}");
            }

            if (expression is MemberExpression memberExpression)
            {
                sb.Append($"{Param}.[{memberExpression.Member.Name}]");
            }
        }

4. 最后执行生成SQL语句，详情请看源码github

5. 调用

        static void Main(string[] args)
        {
            using (var context = new TestContext())
            {
                var list = context.User.Select<UserModel>().ToList();

                var user1 = context.User.AsNoTracking().FirstOrDefault(x => x.Id == 2);

                Console.WriteLine($"-----------Before Update --------------------");
                Console.WriteLine($"{user1.Id}:{user1.Name}:{user1.RoleId}");

                context.User.Where(x => x.Id == 2).RestValue(x => x.Name == (x.Name + " Add Bob") && x.RoleId == (x.RoleId + 1));

                var user2 = context.User.AsNoTracking().FirstOrDefault(x => x.Id == 2);

                Console.WriteLine($"-----------After Update --------------------");
                Console.WriteLine($"{user2.Id}:{user2.Name}:{user2.RoleId}");
            }
            Console.WriteLine($"------------结束--------------------");
            Console.ReadLine();
        }

6. 生成的SQL如下

     UPDATE [x] SET x.[Name] =x.[Name] + @param_0 ,x.[RoleId] =x.[RoleId] + @param_1
     FROM [User] AS [x]
     WHERE [x].[Id] = 2