In this example I want to add a .loop({quantity},{sleepvalue}) to a method I got it to work with this: this.loop(count, 500, ()=>{ var image = Screenshots.getScreenshotOfDesktop(); pictureBox.load(image); images.Add(image); updateTrackBar(); }); using this extension method: public static void loop(this Object _object...
Does anyone know if it is possible to exit a generic ForEach that uses lambda? e.g. someList.ForEach(sl => { if (sl.ToString() == "foo") break; // continue processing sl here // some processing code } ); This code itself won't compile. I know I could use a regular foreach but for consistency I want to use lamb...
I'm trying to change the integer values in a vector using transform and an if_then_else control structure from Boost Lambda. However my compiler is not appreciating my efforts. The code I am attempting is: transform(theVec.begin(), theVec.end(), theVec.begin(), if_then_else(bind(rand) % ratio == 0, _1 = bind(rand) % maxSize, ...
Hi All, How can I get the name of the first method called from an expression in C#? Something like the fictional MethodUtils.NameFromExpression() below: Expression<Action<string>> expr = s => s.Trim(); Assert.AreEqual("Trim", MethodUtils.NameFromExpression(expr)); Ideally any util method would be written/overloaded in such a way tha...
I have a class with an overloaded method: MyClass.DoThis(Action<Foo> action); MyClass.DoThis(Action<Bar> action); I want to pass a lambda expression to the Action version: MyClass.DoThis( foo => foo.DoSomething() ); Unfortunately, Visual Studio rightly cannot tell the difference between the Action<Foo> and Action<Bar> versions, due...
I have a lite problem i don't really know how to fix. In my example below i would like to select a list of ProductCategories with ProductItems that are active. public IEnumerable<ProductCategory> ListProductCategories() { return _entities.ProductCategorySet.Include("ProductItems").Where(x => x.ProductItems.Active == ...
I implemented a version of the str_replace function available in php using python. Here is my original code that didn't work def replacer(items,str,repl): return "".join(map(lambda x:repl if x in items else x,str)) test = "hello world" print test test = replacer(test,['e','l','o'],'?') print test but this prints out hello world ...
I'm trying to implement undo functionality with C# delegates. Basically, I've got an UndoStack that maintains a list of delegates implementing each undo operation. When the user chooses Edit:Undo, this stack pops off the first delegate and runs it. Each operation is responsible for pushing an appropriate undo delegate unto the stack. So ...
I have a function which creates a different type of expression depending on the value of the variable passed in. Protected Function BuildSortPredicate(ByVal tableType As Object, ByRef expr As Expression) Dim sortExpression As Expression If tableType Is "Job" Then sortExpression = Expression.Lambda(Of Func(Of Job, String)...
This is a purely academic question, but what's the difference between using == and .Equals within a lambda expression and which one is preferred? Code examples: int categoryId = -1; listOfCategories.FindAll(o => o.CategoryId == categoryId); or int categoryId = -1; listOfCategories.FindAll(o => o.CategoryId.Equals(categoryId)); ...
I have a data structure defined as: Dictionary<Guid, List<string>> _map = new Dictionary<Guid, List<string>>(); I'm trying to create a lambda expression that given a string, returns a IEnumerable of Guids associated with any List<string> containing that string. Is this reasonable/possible or should I use a more appropriate data...
I want to check whether a simple mathematical expression would overflow (using checked and catch(OverflowException)), but without the need to use a try-catch block every time. So the expression (not the result!) should be passed to a function checkOverflow, which then acts accordingly in case of an overflow. This is what I attempted, bu...
Not having them used them all that much I'm not quite sure all that lambdas/blocks can be used for (other than map/collect/do/lightweight local function syntax). If some people could post some interesting but somewhat understandable examples (with explanation). preferred languages for examples: python, smalltalk, haskell ...
I'm trying to get my head around lambda expressions, closures and scoping in Python. Why does the program not crash on the first line here? >>> foo = lambda x: x + a >>> foo(2) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 1, in <lambda> NameError: global name 'a' is not defined >>> a = ...
I have heard of deferred evaluation in python (for example here), is it just referring to how lambdas are evaluated by the interpreter only when they are used? Or is this the proper term for describing how, due to python's dynamic design, it will not catch many errors until runtime? Or am I missing something entirely? ...
Recently I started playing around with Python and I came around something peculiar in the way closures work. Consider the following code: adders= [0,1,2,3] for i in [0,1,2,3]: adders[i]=lambda a: i+a print adders[1](3) It builds a simple array of functions that take a single input and return that input added by a number. The funct...
I'm trying to write a finalizer for Python classes that have circular references. I found out that weak reference callbacks are the way to go. Unfortunately, it seems the lambda I use as a callback is never called. For example, running this code: def del_A(name): print('An A deleted:' + name) class A(object): def __init__(self,...
I am fairly new to using the Expression namespace and was wondering if anyone can share their knowledge. I have created a generic class RuleSet which has the following method. I am using the method to register a function against a property that belongs to type T, this check isn't in place, after extracting the property i invoke the rul...
I am in the process of writing something that will use Linq to combine results from my database, via Linq2Sql and an in-memory list of objects in order to find out which of my in-memory objects match something on the database. I've come up with the query in both expression and query syntax. Expression Syntax var query = order.Items.Jo...
Okay, my guess is this is answered somewhere already, and I'm just not quite familiar enough with the syntax yet to understand, so bear with me. The users of my web app need to filter a long list of items in a gridview, accessed via a linqdatasource. I am using the OnSelecting Event to further filter items. I want to filter those item...