如何使用C＃和Linq实现动态搜索功能？

Question

I am trying to implement a dynamic search functionality in C#. My search will be like

Attribute operand Value === > Height > 170 

Like the above search list goes on dynamically as user can add as much as he wants to filter that data. And Attribute matches my Column name might be from different tables in SQL DB.

What is the best way to implement these kind of searches? I am pretty new to Linq and I am trying to understand http://www.albahari.com/nutshell/predicatebuilder.aspx

How can I dynamically build query or What will be the best way for these sort of searches which is easy to maintain?

Example:

Attribute operand Value === > Height = 170 
Attribute operand Value === > Altitude > 40000  
Attribute operand Value === > temperature < 105 

Everything is customizable to user and build at run time .

What is the best way to implement this ?

Answer 1

Check this answer in this question for an example on how to build an expression dynamically.

In your case I think something like this should help (wrote this off top of my head, pls excuse syntax errors).

PropertyInfo propInfo = typeof(T).GetProperty(Attribute);
ParameterExpression pe = Expression.Parameter(typeof(Attribute), Attribute);
Expression right = Expression.Parameter(typeof(int), Value);
Expression predicateBody = Expression.GreaterThan(left, right);

Expression<Func<int, bool>> lambda1 =
                Expression.Lambda<Func<int, bool>>(
                    predicateBody,
                    new ParameterExpression[] { numParam });

Reference - Expression Trees and ExpressionType .