expression-trees

问题 Suppose I have a type like this: class Context { SomeType[] Items { get; set; } } I want to be able to access specific Items elements using expression trees. Suppose I need an element at index 0 . I can do it like below, where everything works as expected: var type = typeof (Context); var param = Expression.Parameter(typeof (object)); var ctxExpr= Expression.Convert(param, context); var proInfo = type.GetProperty("Items"); Expression.ArrayIndex(Expression.Property(ctxExpr, proInfo),

问题 Let's say I have the 3 followings DTOs public class Mailing { public long Id { get; set; } //... public long IdSender { get; set; } public Sender Sender { get; set; } public long IdTemplate { get; set; } public Template Template { get; set; } } public class Sender { public long Id { get; set; } public string Email { get; set; } //... } public class Template { public long Id { get; set; } public string Name { get; set; } //... } And I have 3 expression trees to manage DAO-to-DTO conversion :

问题 Using EF6, how would I bind a given Expression<Func<Row, string>> argument to an existing select expression, without having to rewrite every property binding using expression trees? public IEnumerable<RowModel> GetRowModels(Expression<Func<Row, string>> textExpr) { return from row in MyDatabaseContext.MyTable select new RowModel { RowID = row.ID, CreatedDate = row.CreatedDate, AnotherProperty = row.AnotherProperty, Text = textExpr, // how do I bind this expression? Value = row.OtherStuff

问题 I need string conversion of an Expression Tree so I create an Expression Tree and use ToString method like this var exp = ((Expression<Func<UserDetailInfo, bool>>) (x => x.OperationID == operationId)).ToString(); but result is strange x => (x.OperationID == value(TCS.Proxy.PermissionProxy+<>c__DisplayClass5).operationId) TCS.Proxy.PermissionProxy is my class in WCF proxy project !!! (I send expression from client to proxy) but when I create this Expression myself everything is good var entity

问题 {- P A R T 2 : Implementation of a parser for Łukasiewicz expressions --TODO Define the type LExpTree, using the constructors L, V, N, Q, S, K, A, O, E, I L for Lukasiewicz literals (i.e. C, I or U) V for Variables (string) N for a node representing the prefix neg Q for a node representing the prefix pos S for a node representing the prefix cer K for a node representing the prefix unk A for a node representing the infix And O for a node representing the infix Or E for a node representing the

问题 I've searched high an low of SO to find a solution for my problem. I've found several answers for when it comes to simple expressions like var exp1 Expression<Func<T, bool>> x => x.Name == "MyName" But I'm having trouble when the expressions are like: var exp1 Expression<Func<T, bool>> x => x.Category.Name == "Coupe" For the simple ones, I am able to convert any expression from one type (T) to another (TT), I need to do it also in the other cases, more complex... Anyone who can help with some

问题 The question hereby refers to my previous question here The Sum() expression advised by @xanatos worked perfectly. I tried also Max() expression for the field of the type double and faced no issue. As the next step I decided to add the DateTime field and calculate Max() for it. I modified the GroupSum class as follows: private class GroupSum : GroupKey { public Double AggN0 { get; set; } public DateTime AggD0 { get; set; } } And programmed the function: private static Func<IGrouping<GroupKey,

问题 I just want to parse simple expressions like - IIF(FVAL(PFC) = TRUE, (IIF((ORGVAL(BAS, "2012/12/31") + ORGVAL(DA)) < 6500, (FVAL(BAS) + FVAL(DA)) * 12%, 780)), 0)` After parsing this I should be able to know what functions contains what parameters. |-FVAL |-PFC |-ORGVAL |-BAS |-"2012/12/31" I'm stuck with .Net Framework 2.0, so no Linq or lambda expression goodies for me. Also I want to include the code in my custom library and not just reference it. Can anyone point me to some good library

问题 public class Entity { public int A { get; set; } public string B { get; set; } } Expression<Func<Entity,object>> expr = x => x.A; Expression<Func<Entity,int>> exprAtRuntime = x => x.A; Expression<Func<Entity,object>> expr2 = x => x.B; Expression<Func<Entity,string>> expr2AtRuntime = x => x.B; How can I take expr and convert it to the type of expr2 at runtime? Likewise, I need to do the same for property B. I need to accept a params array of type Expression<Func<Entity,object>> which

问题 I have a method that takes IQueryable<T> and I want to implement OrderBy generically inside it. Ideally by passing in c => c.SomeProperty in as a parameter but I can't figure out how to get the generics working on that so I've tried it with a string. However I am getting the error: Incorrect number of parameters supplied for lambda declaration This is what I tried (using the string method) var sortSelectorParameter = Expression.Parameter(typeof(T), "c"); var sortSelector = Expression