Expression Tree Tutorial - Knowledge Base (KB)
542 results for: in tag: c#
Identify an event via a Linq Expression tree
The compiler usually chokes when an event doesn't appear beside a ...+=... or a ...-=..., so I'm not sure if this is possible....I want to be able to identify an event by using an Expression tree, so I can create an event watcher for a test. The syntax wo...
asked by Will
Try-catch every line of code without individual try-catch blocks
I do not currently have this issue..., but you never know, and thought experiments are always fun....Ignoring the obvious problems that you would have to have with your architecture to even be attempting this..., let's assume that you had some horribly-wr...
asked by tags2k
Serializing and Deserializing Expression Trees in C#
Is there a way to Deserialize Expressions in C#, I would like to store Expressions in a Database and load them at run time.
asked by Alexandre Brisebois
How do I create an expression tree to represent 'String.Contains("term")' in C#?
I am just getting started with expression trees so I hope this makes sense. I am trying to create an expression tree to represent:...t => t.SomeProperty.Contains("stringValue"); ...So far I have got:... private static Expression.Lambda<Func<string, boo...
asked by flesh
Best way to call an instance method in Expression Trees?
What is the best way to call an instance method within an Expression Tree? My current solution is something like this for an interface method "object GetRowValue(rowIndex)" of the interface IColumn....public static Expression CreateGetRowValueExpression( ...
asked by Rauhotz
Lambda Expression Tree Parsing
I am trying to use Lambda Expressions in a project to map to a third party query API. So, I'm parsing the Expression tree by hand....If I pass in a lambda expression like:...p => p.Title == "title" ...everything works....However, if my lambda expression l...
asked by Keith Fitzgerald
Expression trees for dummies?
I am the dummy in this scenario....I've tried to read on Google what these are but I just don't get it. Can someone give me a simple explanation of what they are and why they're useful?...edit: I'm talking about the LINQ feature in .Net.
asked by Dave
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
C# How to convert an Expression<Func<SomeType>> to an Expression<Func<OtherType>>
I have used C# expressions before based on lamdas, but I have no experience composing them by hand. Given an ...Expression<Func<SomeType, bool>> originalPredicate..., I want to create an ...Expression<Func<OtherType, bool>> translatedPredicate.......In th...
asked by Michiel van Oosterhout
In LINQ to SQL, how do you pass parts of a LINQ query into a function
Is it possible to pass parts of a linq Query into a function? I want create a common interface for my DAL that always uses the same query interface. For example, ...List<T> Get(Join j, Where w, Select s){ return currentDataContext<T>.Join(j).Wh...
asked by Arron S
C#: How to parse arbitrary strings into expression trees?
In a project that I'm working on I have to work with a rather weird data source. I can give it a "query" and it will return me a DataTable. But the query is not a traditional string. It's more like... a set of method calls that define the criteria that I ...
asked by Vilx-
How to create LINQ Expression Tree to select an anonymous type
I would like to generate the following select statement dynamically using expression trees:...var v = from c in Countries where c.City == "London" select new {c.Name, c.Population}; ...I have worked out how to generate...var v = from c in ...
asked by Tom Deloford
C# Expression Tree Parameter for Parent Navigation Property
How can I create a ParameterExpression for the parent side of a 1 to * Navigation Property?...The following works for the child entity:...var parameter = Expression.Parameter( typeof(T), // where T is the entity type GetParameterName()); // helper...
asked by blu
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
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
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 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
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
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