expression-trees

I've tried to simplify this example, as the actual code I'm playing with is more complex. So while this example may seem silly, bear with me. Let's say I'm working with the AdventureWorks database and I decide I want to add a property called Blarg to the Product table that returns an expression that contains code I would like to use in several places: public partial class Product { public Expression<Func<Product, string>> Blarg { get { return product => product.ProductModelID.HasValue ? "Blarg?" : "Blarg!"; } } } What I want to do is create an expression expression tree, have it get the

I need to filter a list of documents by passing them to a custom filter that I'm struggling to build dynamically using a foreach loop : var mainPredicate = PredicateBuilder.True<Document>(); // mainPredicate is combined to other filters successfully here ... var innerPredicate = PredicateBuilder.False<Document>(); foreach (var period in periods) { var p = period; Expression<Func<Document, bool>> inPeriod = d => d.Date >= p.DateFrom && d.Date <= p.DateTo; innerPredicate = innerPredicate.Or(d => inPeriod.Invoke(d)); } mainPredicate = mainPredicate.And(innerPredicate); This last line : documents

I'm a newbie when it comes to expression trees, so I'm not sure how to ask this question or what terminology to use. Here's an overly-simplifed version of what I'm trying to do: Bar bar = new Bar(); Zap(() => bar.Foo); public static void Zap<T>(Expression<Func<T>> source) { // HELP HERE: // I want to get the bar instance and call bar.Zim() or some other method. } How can I get to bar inside the Zap method? Since the expression passed into your Zap method is a tree, you just need to walk the tree using an Expression Tree Visitor and look for the first ConstantExpression in the expression. It

I'm try'n to create a dynamic query tool using System.Linq.Expressions.Expression (WPF/c#4.0) It runs against an OData Service. So far, all is working as long as I limit the conditions to build in options like Equal(..), GreaterThan(..) etc. There seems to be no build in contains/Like condition so I tried building my own. There are a handful of articles already out there. One I tried is How to create a System.Linq.Expressions.Expression for Like? . Now if I use the above solution, the resulting where expression is whereCallExpression = {Convert([10000]).Expand("A,B").Where(clt => MyLike(clt

I’m working on some expression tree code written by a colleague and am looking into the possibility of adding additional expressions. It currently supports: equals, not-equals, IsNull etc. I need to add something that will allow it to use a wildcard comparison similar to the SQL “Like” command or using regular expressions. At the moment the code parses an XML file and extracts the data which is then processed using code similar to the line shown below. This is an example of the “Equal” expression. “callExp” is a MemberExpression that basically holds the field name of my table (Entities) and

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<object>> func ) { return ((MethodCallExpression)func.Body).Method; } But I get this exception: "Cannot bind to the target method because its signature or security transparency is not compatible with that of the delegate type." What will work? Note that CreateDelegate was moved, for this profile at least, since the previous version of .NET. Now it's

I have an expression in the format of Expression<Func<T, T2, bool>> that I need to convert into an expression on the format of Expression<Func<T2, bool>> by replacing the T in the first expression with a constant value. I need this to stay as an expression so I can't just Invoke the expression with a constant as the first parameter. I've looked at the other questions here about expression trees but I can't really find a solution to my problem. I suspect I have to walk the expression tree to introduce the constant and remove one parameter but I don't even know where to start at the moment. :(