What is a decent use case for Expression Trees in.net 4.0?

.net expression-trees linq

Question

This one was inspired by my language-guru co-worker who can't seem to find a good use for them, and after a few lame attempts of my own, I'd have to agree.

Now I know these concepts tend to flow a lot more easily once you get some good practical reasons down.

At the moment it seems as though its only purpose is to allow you to write a Linq provider?

Is that it?? Is there any other benefits to this?

1
17
10/7/2009 4:07:54 PM

Fastest Entity Framework Extensions

Bulk Insert
Bulk Delete
Bulk Update
Bulk Merge

Accepted Answer

Expression tree are so powerful because they let you treat code like data. Users are accustomed to building up data, saving it and coming back to it later.

Expression trees let you do the same thing with code. For example you can take your user's input (check-boxes, number ranges, etc.) and translate it into an Expression tree. That expression tree can then be executed, or stored off for later use. Very cool.

Think of the practical uses around reporting like building up and saving data filters and data mappings. Another practical use would be to support custom work flows in your application based on user defined rules.

Here's a bit of MSDN code on serializing expression trees (http://code.msdn.microsoft.com/exprserialization) that should get the ideas flowing.

17
10/7/2009 4:45:11 PM

Popular Answer

You can use Expression Trees to transform a domain language into executable code.

ChaosPandion

Related Questions

.NET 4.0 Expression Trees: Expression The method "get Item" in type ListT> cannot be found.

I'm stuck with the problem below and wondering is someone out there will be able to help. I have added comments to the code to make it self-explanatory but let me know if you need more info or if the problem is unclear....Thanks a lot in advance!...Edit: I've been asked to summarize the problem in text, so here it goes: under the circumstances desc...
.net-4.0 c# expression-trees lambda
asked by d..

Expression trees vs. CodeDom in C# 4.0

Expression trees have a lot in common with (for example) an ...AST.... It doesn't map directly to code, but is very amenable to construction from algorithms. For example, if you are parsing a formula:...((a + 2) / b) ...that is:...ParameterExpression a = ..., b = ... var body = Expression.Divide( Expression.Add(a, Expression.Constant(2)), b...
c# codedom expression-trees
asked by Marc Gravell

An expression tree may be sent as a parameter to another expression tree.

I have two expression trees defined like this:...private Expression<Func<TEntity, TPropertyResult>> PropertyAccessor { get; set; } ...and...private Expression<Func<TPropertyResult, bool>> TestExpression { get; set; } ...I need to create a new expression tree that will result in the equivalent of:...var expression = p => this.TestExpression(this.Pro...
c# expression-trees lambda
asked by Pierre-Alain Vigeant

Using Expression and creating Expression Trees Method to invoke

I have two dummy classes named ...TClass1... and ...TClass2.... I would like to know how to build an expression tree to call the operation ...TClass1.TestMethod.... I specifically have problem using ...Expression.Call... method to create an expression based on instance methods of a class. Any help would be appreciated....public class TClass1 { ...
c# expression-trees
asked by Hamid Rashidi

How can I create a LINQ-friendly 'return false' expression using C# expression trees?

Can you wrap the entire thing in an if-else expression?...Meaning:...if input return <your normal code> else return false ...The return is implicit in expressions; the return value of the expression will simply be the last value. So you could try:... Expression.Condition ( Expression.NotEqual(input, Expression.Constant("")), ...
.net c# expression-trees linq
asked by JulianR

Building an expression tree using a stack and a binary tree c

I am given an arithmetic formula containing operators +, -, *, / and parentheses (which might or might not change the natural precedence of operators). An example would be the following one: a / b + f – (c + d) * e – a * c. and I am asked to use a stack (implemented as a linked list) in order to keep track of the operands and the operators: an...
binary-tree c expression-trees stack
asked by user1680944

Efficiently eliminate common sub-expressions in .NET Expression Tree

You're correct in noting this is not a trivial problem....The classical way that compilers handle it is a ...Directed Acyclic Graph (DAG) representation... of the expression. The DAG is built in the same manner as the abstract syntax tree (and can be built by traversing the AST - perhaps a job for the expression visitor; I don't know much of C# li...
.net algorithm c# expression-trees optimization
asked by Gene

How to call a lambda using LINQ expression trees in C# / .NET

I want to use expression trees to dynamically create a method to call a lambda. The following code runs fine for the first call to the ComposeLambda function, but the second call fails with the following error message....Incorrect number of arguments supplied for call to method 'Int32 lambda_method(System.Runtime.CompilerServices.Closure, Int32)'...
.net c# expression-trees lambda linq
asked by Philipp Kramer

Create Lambda Expression Selector For New Class Using Expression Tree

Related To:...Create Expression Tree For Selector...Create a Lambda Expression With 3 conditions...Convert Contains To Expression Tree...Convert List.Contains to Expression Tree...I want to Create ...Selector... expression using ...Expression Tree... for new class. Please Consider this code:...s => new Allocation { Id = s.Id, ...
c# c#-6.0 expression-trees lambda linq
asked by Arian

C# Expression Tree with Ignore Case or tolower

I want to create expression.Equal() with ignore case. Sample code:...if (!string.IsNullOrEmpty(request.BrandCode)) { MemberExpression me = Expression.Property(parmExpression, "BrandCode"); ConstantExpression constant = Expression.Constant(request.BrandCode, typeof(string)); expbrandCode = Expression.Equal(me, constant); } if (!string.I...
.net asp.net c# expression-trees
asked by RajGan

Fastest Entity Framework Extensions

Bulk Insert
Bulk Delete
Bulk Update
Bulk Merge
View more on Stack Overflow

Prime Library

Performance

Expression Evaluator

More Projects...
Licensed under: CC-BY-SA with attribution
Not affiliated with Stack Overflow
Licensed under: CC-BY-SA with attribution
Not affiliated with Stack Overflow