Expression Tree Tutorial - Knowledge Base (KB)
45 results in tag: reflection
Advice on C# Expression Trees
I'm working on a method that accepts an expression tree as a parameter, along with a type (or instance) of a class....The basic idea is that this method will add certain things to a collection that will be used for validation....public interface ITestInte...
asked by Ian P
Given a type ExpressionType.MemberAccess, how do i get the field value?
I am parsing an Expression Tree. Given a NodeType of ExpressionType.MemberAccess, how do I get the value of that Field? ...From C# MSDN docs: MemberAccess is A node that represents reading from a field or property. ...A code snippet would be incredibly, ...
asked by Keith Fitzgerald
Creating an expression tree that calls a method
Is it possible to create an expression tree that directly calls a method? For example, consider the following method:...public static int MyFunc(int a, int b) { return a + b; } ...I would like to create an expression tree that calls MyFunc with parame...
asked by brianberns
Convert func to predicate using reflection in C#
I'm basically trying to do ...this..., but I don't know what T will be, so I'm building things up using Reflection and Expression trees....// Input (I don't know about "Book") Type itemType = typeof(Book); // Actual Code // Build up func p => p.AuthorNam...
asked by Jon Smock
Why are expression trees safer than reflection?
In ...this... answer to the question of the fastest way to determine if a property contains a given attribute, user ...Darin Dimitrov... posited that expression trees are safer than reflection. Is this true, and if so, why is it true?
asked by Charles Y.
How to reflect over T to build an expression tree for a query?
I'm trying to build a generic class to work with entities from EF. This class talks to repositories, but it's this class that creates the expressions sent to the repositories. Anyway, I'm just trying to implement one virtual method that will act as a base...
asked by Gup3rSuR4c
How do I rewrite query expressions to replace enumerations with ints?
Inspired by a desire to be able to use enumerations in EF queries, I'm considering adding an ExpressionVisitor to my repositories that will take incoming criteria/specifications criteria and rewrite them to use the corresponding persisted int property....
asked by Morten Mertner
How to convert Expression<Func<T, bool>> to Expression<Func<Type, bool>>?
I am trying build a dictionary of Expressions that have different input parameter types. I am trying to store the type of the parameter because later down the road I plan to use Reflection to discover a method on the type. Here is the code that creates th...
asked by Rockdocta
Expression tree for String.IndexOf method
How should I construct Expression tree for ...string.IndexOf("substring", StringComparison.OrdinalIgnoreCase)...?...I can get it working without the second argument: ...StringComparison.OrdinalIgnoreCase.... These are my attempts so far:...var methodCall ...
asked by ashokgelal
Get actual return type from a Expression<Func<T, object>> instance
I have a method that accepts a ...Expression<Func<T, object>>... instance. I want to get at the ...actual... data type being returned by a specific expression instance, rather than ...object.......I can get it to work for direct property references, so if...
asked by Seth Petry-Johnson
Expressions call constructor with a parameter and set its value
i am trying to call an parameterized constructor from an expression instead of using the default ctor. this is the code that gets the constructor parameter(s):...ConstructorInfo ci = type.GetConstructor(BindingFlags.Instance | BindingFlags.Public, null, C...
asked by user1052087
Extract method name from expression tree?
I am trying to implement the following pattern function:...MethodInfo GetMethod( Expression<Func<TTarget, EventHandler<TEventArgs>>> method) ...I can provide an instance of TTarget if required...The desired usage is:...public static void Main(stri...
asked by Shimmy
How to call a non-generic static extension method with parameters using Reflection
I am using the code below to execute methods. It works for standard methods of ...string... , for example ...StartsWith..., however I am attempting to use several string extension methods, including an override for ...Contains... which alllows for case-in...
asked by Rory McCrossan
Getting PropertyInfo Name and Value
I have seen various ways of doing this including reflection, component model type descriptors, expression trees, and aspects, BUT I'm still not sure whether the code below achieves all of the following objectives using .Net 4.0 or higher:...Be type safe, ...
asked by Berryl
Create delegate from constructor
Using reflection, I'm trying to create a delegate from a parameterless constructor like this:...Delegate del = GetMethodInfo( () => System.Activator.CreateInstance( type ) ).CreateDelegate( delType ); static MethodInfo GetMethodInfo( Expression<Func<obje...
asked by HappyNomad
How to set properties and nested property's properties with expression
I googled the propblem and also search the SO. There is a ton of solutions that all of them (that I found) are not completed. Can you help me please, to set a class's properties and its nested property's properties, choosen by a ...lambda..., using ...Ref...
asked by agent47
How can I simplify Linq extension method invokation using reflection?
Background:...I have a web service that returns the rows in a table (table name supplied as a parameter) with Ids greater than a certain Id (also supplied as a parameter). We are assuming the Ids are sequential....I am using Linq to SQL for database inter...
asked by Ryan Kirkman
Use Compiled Lambda expression instead of Activator.CreateInstance to initialize SoapHttpClientProtocol object
I'm working with the code that dynamically instantiates ...SoapHttpClientProtocol... object (proxy class) and uses this object to make a call to WS-Basic I Web Service. Here is the simplified version of my code:...public override object Call(Type callingO...
asked by Misha Narinsky
Casting the Expression.Property result
How do I create a cast when creating an ...Expression... tree dynamically?...The problem is, I have a property of type ...string...:...public class Test { public string Id { get; set; } } ...And I want to generically create a strongly typed lambda exp...
asked by Lou
Dynamic lambda select expression
I have a lambda expression tree issue that I can’t figure out. I am trying to make a dynamic linq Select statement....I have a dynamic repository created here:...private static dynamic GetRepository(Type type) { dynamic repository = typeof(IFactory)...
asked by Morten Holmgaard
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