EDIT: The list below applies to C# anonymous types. VB.NET has different rules – in particular, it can generate mutable anonymous types (and does by default). Jared has pointed out in the comment that the naming style is different, too. Basically this is all pretty fragile… You can’t identify it in a generic constraint, but: … Read more
You’re close, but you have to be aware that anonymous types don’t have default constructors. The following code prints { Name = def, Num = 456 }: Type anonType = new { Name = “abc”, Num = 123 }.GetType(); var exp = Expression.New( anonType.GetConstructor(new[] { typeof(string), typeof(int) }), Expression.Constant(“def”), Expression.Constant(456)); var lambda = LambdaExpression.Lambda(exp); object … Read more
The trick is to create a comparer that only works on inferred types. For instance: public class Comparer<T> : IComparer<T> { private Func<T,T,int> _func; public Comparer(Func<T,T,int> func) { _func = func; } public int Compare(T x, T y ) { return _func(x,y); } } public static class Comparer { public static Comparer<T> Create<T>(Func<T,T,int> func){ return … Read more
Anonymous types are immutable, ValueTuples are not. This is reflected in the fact that anonymous types expose properties, ValueTuples expose fields. Data binding almost always requires properties. Plenty of existing code only works with reference types, not with value types. What in particular comes to mind are projections in Entity Framework: projections to value types … Read more
Well, you could use: var list = anBook.Select(x => new ClearBook { Code = x.Code, Book = x.Book}).ToList(); but no, there is no direct conversion support. Obviously you’ll need to add accessors, etc. (don’t make the fields public) – I’d guess: public int Code { get; set; } public string Book { get; set; } … Read more
Of course, by creating the tuple from your LINQ expression: public (int id, string name) GetSomeInfo() { var obj = Query<SomeType>() .Select(o => (o.Id,o.Name)) .First(); return obj; } According to another answer regarding pre-C# 7 tuples, you can use AsEnumerable() to prevent EF to mix things up. (I have not much experience with EF, but … Read more
No there is no supported C# syntax which will produce anonymous structs
Anonymous type properties are read only and they cannot be set. Anonymous types provide a convenient way to encapsulate a set of read-only properties into a single object without having to explicitly define a type first. The type name is generated by the compiler and is not available at the source code level. The type … Read more
You have to use a typed null: (List<Plane>)null Or (Plane[])null Otherwise the compiler has no idea what type you want the anonymous type’s member to be. Update As @AakashM has rightly pointed out – this solves your problem of assigning a null to an anonymous member – but doesn’t actually compile – and if it … Read more
You can create an empty list for anonymous types and then use it, enjoying full intellisense and compile-time checks: var list = Enumerable.Empty<object>() .Select(r => new {A = 0, B = 0}) // prototype of anonymous type .ToList(); list.Add(new { A = 4, B = 5 }); // adding actual values Console.Write(list[0].A);