中文字幕精品亚洲无线码二区,国产黄a三级三级三级看三级,亚洲七七久久桃花影院,丰满少妇被猛烈进入,国产小视频在线观看网站

Lind.DDD.ExpressionExtensions動態(tai)構建(jian)表達(da)式樹，實現對數據(ju)集的權限控(kong)制(zhi)

回到目錄

Lind.DDD框架里提出了(le)對數據集(ji)的(de)(de)控(kong)制(zhi)，某些權限的(de)(de)用戶為(wei)某些表添(tian)加某些數據集(ji)的(de)(de)權限，具體(ti)實(shi)現是在一張表中存儲用戶ID,表名(ming)，檢索字段，檢索值和檢索操(cao)作(zuo)符(fu)，然(ran)后(hou)用戶登陸后(hou)，通過自己權限來構建對應表的(de)(de)查(cha)詢語句(ju)，即動態構建表達式樹，這種操(cao)作(zuo)一些被寫在業(ye)務(wu)層上，我們可以在業(ye)務(wu)層需(xu)要進行數據集(ji)權限控(kong)制(zhi)的(de)(de)地方，添(tian)加這種策略，下面(mian)具體(ti)分析說明(ming)一下．

看一下數(shu)據集(ji)權限表結(jie)果

  public class User_DataSet_Policies
    {
        /// <summary>
        /// 用戶ID
        /// </summary>
        public int UserId { get; set; }
        /// <summary>
        /// 表名(ming)
        /// </summary>
        public string TableName { get; set; }
        /// <summary>
        /// 策略(lve)所需字(zi)段
        /// </summary>
        public string PolicyField { get; set; }
        /// <summary>
        /// 策略所(suo)需要(yao)值(zhi)
        /// </summary>
        public string PolicyValue { get; set; }
        /// <summary>
        /// 策略操(cao)作符(fu)
        /// </summary>
        public string PolicyOperation { get; set; }
    }

看一下，在程(cheng)序(xu)中如何動態構建和(he)使用我們的表達式樹(shu)

 　　　　　　 Expression<Func<User, bool>> exe = ExpressionExtensions.GenerateExpression<User>(
                new string[] { "Age", "UserName" },
                new object[] { "12", "zzl" },
                new string[] { "=", "=" });
            userList.Where(exe.Compile()).ToList().ForEach(i =>
            {
                Console.WriteLine(i.UserName);
            });

下面(mian)貢獻一(yi)下GenerateExpression泛型(xing)方法的(de)原碼(ma)，大家可以把它添(tian)加(jia)到我們的(de)LinqExtensions模塊里(li)

　　 /// <summary>
    /// 表(biao)達式樹的擴展
    /// </summary>
    public class ExpressionExtensions
    {
        /// <summary>
        /// 構建表達式(shi)樹
        /// 調用：GenerateExpression(new string[]{"username"},new object[]{"zzl"},new string[]{"="});
        /// </summary>
        /// <typeparam name="T">表類(lei)型(xing)</typeparam>
        /// <param name="keys">字(zi)段名</param>
        /// <param name="values">字(zi)段值</param>
        /// <param name="operation">操作(zuo)符(fu)</param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> GenerateExpression<T>(string[] keys, object[] values, string[] operation)
        {
            var TType = typeof(T);
            Expression expression_return = Expression.Constant(true);
            ParameterExpression expression_param = Expression.Parameter(TType, "p");
            Expression expression;
            for (int i = 0; i < keys.Length; i++)
            {
                switch (operation[i])
                {
                    case "=":
                        expression = Expression.Equal(Expression.Call(Expression.Property(expression_param, TType.GetProperty(keys[i])),
                            TType.GetMethod("ToString")),
                         Expression.Constant(values[i]));
                        expression_return = Expression.And(expression_return, expression);
                        break;
                    case "%":
                        expression = Expression.Call(Expression.Property(expression_param, TType.GetProperty(keys[i])),
                            typeof(string).GetMethod("Contains"),
                            Expression.Constant(values[i], typeof(string)));
                        expression_return = Expression.And(expression_return, expression);
                        break;
                    case ">":
                        expression = Expression.Call(Expression.Property(expression_param, TType.GetProperty(keys[i])),
                            typeof(double).GetType().GetMethod("GreaterThan"), Expression.Constant(values[i]));
                        expression_return = Expression.And(expression_return, expression);
                        break;
                    case "<":
                        expression = Expression.Call(Expression.Property(expression_param, TType.GetProperty(keys[i])),
                            typeof(double).GetType().GetMethod("LessThan"), Expression.Constant(values[i]));
                        expression_return = Expression.And(expression_return, expression);
                        break;
                    case ">=":
                        expression = Expression.Call(Expression.Property(expression_param, TType.GetProperty(keys[i])),
                            typeof(double).GetType().GetMethod("GreaterThanOrEqual"), Expression.Constant(values[i]));
                        expression_return = Expression.And(expression_return, expression);
                        break;
                    case "<=":
                        expression = Expression.Call(Expression.Property(expression_param, TType.GetProperty(keys[i])),
                            TType.GetProperty(keys[i]).GetType().GetMethod("LessThanOrEqual"), Expression.Constant(values[i]));
                        expression_return = Expression.And(expression_return, expression);
                        break;
                    case "in":
                        string[] strarr = values[i].ToString().Split(',');
                        Expression or_return = Expression.Constant(false);
                        for (int k = 0; k < strarr.Length; k++)
                        {
                            expression = Expression.Equal(Expression.Call(Expression.Property(expression_param, TType.GetProperty(keys[i])),
                                TType.GetMethod("ToString")),
                             Expression.Constant(strarr[k]));
                            or_return = Expression.Or(or_return, expression);
                        }

                        expression_return = Expression.And(expression_return, or_return);
                        break;
                    default:
                        throw new ArgumentException("無效的操作(zuo)符，目前(qian)只(zhi)支持=,%,>,<,>=,<=,in");
                }
            }

            return (Expression<Func<T, bool>>)Expression.Lambda<Func<T, bool>>(expression_return, new ParameterExpression[] { expression_param });
        }
    }

對于動態構建表達(da)式的介紹就(jiu)到這里了，以后在使(shi)用(yong)過程中如(ru)果出現什么問題(ti)，請直接回復我．

回到目錄

posted @ 2015-12-30 09:06  張占嶺  閱讀(1445)  評論(0)    收藏  舉報