linq-expressions

I'm currently working with ASP Dynamic Data for the first time and I'm trying to build a filter. Our users have a need to locate items in a list based upon whether or not the item is a child of a selected parent (our items can have more than one parent). The items in question are Segments and each Segment has a property called RouteIds, of type IEnumerable, which is a collection of all of the Segment's parent Ids. I've gotten to this point in overriding the GetQueryable method in my filter, but I keep getting exceptions thrown on the last line shown: ConstantExpression ce = Expression.Constant

I am attempting to create an Expression that will invoke a specific generic overloaded method ( Enumerable.Average in my first test case). The specific type bindings are not known until runtime however so I need to use Reflection to find and create the correct generic method (the Expression is being created from parsed text). So if I know at runtime that I want to find this specific overload: public static double Average<TSource>(this IEnumerable<TSource> source, Func<TSource, int> selector) How do I resolve that particular MethodInfo using reflection? So far I have the following selection

I'm trying to call String.Format from with in a Linq.Expression tree. Here's a quick example: var format = Expression.Constant("({0}) {1}"); var company = Expression.Property(input, membernames.First()); var project = Expression.Property(input, membernames.Last()); var args = new Expression[] {format, company, project}; var invoke = Expression.Call(method,args); The issue however is that String.Format has the signature of: String.Format(string format, params object[] args) and I'm trying to pass in Expression[]. Now I could go through all the trouble of creating an array, populating it with

I try do implement a user dynamic filter, where used selects some properties, selects some operators and selects also the values. As I didn't find yet an answer to this question , I tried to use LINQ expressions. Mainly I need to identify all houses which main rooms are kitchens(any sens, I know). using System; using System.Collections.Generic; using System.Linq; using System.Linq.Expressions; //using System.Linq.Dynamic; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { Room aRoom = new Room() { Name = "a Room" }; Room bRoom = new Room() { Name = "b Room" };

Hello, I am using LINQ and EF with C# 4.0. I have dragged the basic ELMAH table into EF (built and saved many many times). All is working as one would expect. But have tried to be too ambitious and need a little help - I am trying to get the Column name from an expression that is passed in as a variable. What I want is this: Pass in : x=>x.ErrorId and get : "ErrorId" public void GetColumnName(Expression<Func<T, object>> property) { // The parameter passed in x=>x.Message // Message works fine (probably because its a simple string) using: string columnName = (property.Body as MemberExpression)