Expression Tree Tutorial - Knowledge Base (KB)
656 results
How do I make a LINQ expression to call a method?
I've been playing around with the ...DLR... a bit and am a bit stuck on calling methods. For example, suppose I want to make an expression to push something onto a stack:...class StackInfo{ protected Stack<SomeClass> _stack; public Expression P...
asked by Jason Baker
How to create custom System.Linq.Expression classes in C#?
Is it possible to create custom Expression classes? If so, does anyone have any examples? Inheriting from the framework abstract Expression class poses a problem in that its constructor takes an ExpressionType parameter, which is a framework enum type - I...
asked by MalcomTucker
Stuck with BinaryExpression in C#
I want to implement...Expression<Func<int, int, int>> Max = (p1,p2) => p1 > p2 ? p1:p2; ...as an expression tree and tried...ParameterExpression LeftEx = Expression.Parameter(typeof(int), "p1"); ParameterExpression RightEx = Expression.Parameter(typeof(in...
asked by Pemo12
expression trees linq get value of a parameter?
AddOptional<tblObject>(x =>x.Title, objectToSend.SupplementaryData); private static void AddOptional<TType>(Expression<Func<TType,string>> expr, Dictionary<string, string> dictionary) { string propertyName; string propertyValue; Expression e...
asked by Tadeusz Wójcik
Help parsing my own expression tree, C#
I have the following code. I constructed an expression tree and I am stuck parsing it to find the result ...You will find the details within my code...public enum OpertaionType { add, sub, div, mul} public class Node { public Node(Node lhs, Node rhs...
asked by mustafabar
Lambda to Expression tree conversion
I will keep it really simple,...How do I get expression tree out of lambda??...or from query expression ?
asked by Prashant Cholachagudda
LINQ-to-SQL Compiled Query Problem (works as uncompiled query)
I have C# extension methods on ...IQueryable..., e.g. ...FindNewCustomers()... and ...FindCustomersRegisteredAfter(int year)... and so forth which I use to "chain" a query together for LINQ to SQL....Now to my problem: I want to create compiled queries, e...
asked by Alex
How to evaluate a standalone boolean expression in a LINQ expression tree
I'm using the standard visitor pattern to iterate through a LINQ expression tree in order to generate dynamic SQL WHERE clauses....My issue is that unlike C#, you can't use a standalone boolean expression in SQL; you have to compare it to either 1 or 0...
asked by Nathan Ridley
C# switch in lambda expression
Is it possible to have a switch in a lambda expression? If not, why? Resharper displays it as an error.
asked by Toto
Parser for query filter expression tree
I am looking for a parser that can operate on a query filter. However, I'm not quite sure of the terminology so it's proving hard work. I hope that someone can help me. I've read about 'Recursive descent parsers' but I wonder if these are for full-blown l...
asked by Lee Atkinson
Java Expression Trees
Is there an equivalent of ....net...'s Expression Trees that underly LINQ for the ...JVM...? I would like to implement some LINQ like code structures in ...Scala... and I am wondering if I have to roll my own expression tree library also....Update: I am n...
asked by Steve Severance
Is there any way to programmatically generate Python bytecode?
I want to hack around with the Python interpreter and try creating a small DSL . Is there any module where I can do something like this theoretical code (similar to LINQ expression trees)? ...expression_tree = Function( Print( String('Hello ...
asked by Jason Baker
Whats a good use case for .net 4.0 Expression Trees?
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 reason...
asked by KevinDeus
iQueryable and Expression Tree
Can anybody explain me how to use (1) iQueryable (2) Expression Tree in C# by providing a very basic example? Both are not correlated, instead of making two separate questions, I wish to clear my doubt in a single question....Advanced Thanks.
asked by user184805
Lambda Parameter not in scope -- while building binary lambda expression
When creating a lambda expression by hand I get a 'Parameter not in scope' exception. ...Any ideas as to what I am doing wrong?... public class OtherType { public string First_Name { get; set; } public string Last_Name { get; set; } ...
asked by TonyAbell
Bit Curious to understand Expression Tree in .NET
I have read several articles and several ...stackoverflow.com... posts about expression tree. It is beating my brain to understand....Questions:... 1) Like DOM (Document Object Model), it is an in-memory representation of logic?...2) Somebody explained it...
asked by user192142
Getting the object out of a MemberExpression?
So, lets say I have the following expression in C#:...Expression<Func<string>> expr = () => foo.Bar; ...How do I pull out a reference to foo?
asked by Brian Genisio
Generated methods for polynomial evaluation
I'm trying to come up with an elegant way to handle some generated polynomials. Here's the situation we'll focus on (exclusively) for this question:...order... is a parameter in generating an ...n...th order polynomial, where n:=order + 1....i... is an in...
asked by Sam Harwell
How do I view an expression tree with LINQPad?
Maybe I'm missing something obvious, but I how can I view the expression tree for this query:...from word in "The quick brown fox jumps over the lazy dog".Split() orderby word.Length select word ...using ...LINQPad...?
asked by GuyBehindtheGuy
Using an expression tree to read the name and value of a property. Is there an alternative?
Assumptions...Suppose I have a class with a property:...class ClassWithProperty { public string Prop { get; private set; } public ClassWithProperty(string prop) { this.Prop = prop; } } ...And now suppose I have created an instance...
asked by Theo Lenndorff
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