.Net 中表达式的转换

.Net 中表达式的转换

 

如： a>0  && (c>a || a <b ) || (a>b || c>1)    转换后  (((a > 0) and ((c > a) OR (a < b))) OR ((a > b) OR (c > 1))) 

本文主要用到了 表达式树（Expression Tree） ， 表达式树相关知识（https://msdn.microsoft.com/zh-cn/library/system.linq.expressions.expression.aspx）  

 

本实例 只是 抛砖引玉， 不足的地方 你们补充。

仍是直接贴代码吧。 

 

        private void button1_Click(object sender, EventArgs e)
        {

            //这里就先写一个吧。 
            Expression<Func<int, int, int, bool>> m = (a, b, c) => a > 0 && (c > a || a < b) || (a > b || c > 1);

            var cccc = AnalysisExpressionTree(m.Body);
            MessageBox.Show("解析后的表达式：" + cccc);


            //再运行一下
            var run = m.Compile();

            var result = run(2, 6, 9);

            MessageBox.Show("数据转换成代码运行后的结果：" + result.ToString());
        }

 

         /// <summary>
        /// 递归解析一下 表达式树
        /// </summary>
        /// <param name="m"></param>
        /// <returns></returns>
        private string AnalysisExpressionTree(Expression m)
        {
            var c = m as ConstantExpression;
            if (c != null)
            {
                return c.Value.ToString();
            }

            var p = m as ParameterExpression;

            if (p != null)
            {


                return p.Name;
            }

            var u = m as UnaryExpression;

            if (u != null)
            {

                if (u.NodeType == ExpressionType.Not)
                {
                    return "!(" + AnalysisExpressionTree(u.Operand) + ")";

                }
            }

            var method = m as MethodCallExpression;


            if (method != null)
            {
                return "调用函数" + method.Method.Name + "(" + string.Join(",", method.Method.GetParameters().Select(pp => pp.Name)) + ")";

            }


            var b = m as BinaryExpression;

            if (b != null)
            {

                switch (b.NodeType)
                {
                    case ExpressionType.And:
                        return "(" + AnalysisExpressionTree(b.Left) + " and " + AnalysisExpressionTree(b.Right) + ")";

                    case ExpressionType.AndAlso:
                        return "(" + AnalysisExpressionTree(b.Left) + " and " + AnalysisExpressionTree(b.Right) + ")";

                    case ExpressionType.GreaterThan:
                        return "(" + AnalysisExpressionTree(b.Left) + " > " + AnalysisExpressionTree(b.Right) + ")";

                    case ExpressionType.LessThan:
                        return "(" + AnalysisExpressionTree(b.Left) + " < " + AnalysisExpressionTree(b.Right) + ")";

                    case ExpressionType.OrElse:
                        return "(" + AnalysisExpressionTree(b.Left) + " OR " + AnalysisExpressionTree(b.Right) + ")";

                    case ExpressionType.NotEqual:
                        return "(" + AnalysisExpressionTree(b.Left) + " != " + AnalysisExpressionTree(b.Right) + ")";

                     //这里还能够再加 ，此例只是一个 DEMO

                }
            }

            return "";

        }

 

 

OK  ， 就写这些吧。 很久不写博客了。源代码  也发出来吧。