Sum The Counts With Lambda Expressions
Feb 3, 2012I have a List(of T) where T has a property that is a list of checkboxes, what I need is a Lambda expression that will count all the checked checkboxes in the list. I tried with:
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C# - Use Or Not Lambda Expressions?
Nov 11, 2009I see lambda expressions have become a very useful tool at some points in the language. I've been using them a lot and most of the time they fit really nice and make the code shorter and perhaps clearer.
Now.. I've seen some , I would say excessive use of them. Some people like them so much that try to use them everywhere they can.. Some times the C# code looks like a functional language. Other factors against are the cost using reflection by lambda and that not friendly to debugging.I would like to hear opinions about how good and how code clear it is to use more or less the lambda expressions. (this is not the better example, but let's say it was the trigger)I was writing the following code. The use of the delegate { return null; } helps me avoid having to ask if the event is null or not every time I have to use it.
public delegate ContactCellInfo.Guest AddGuest();
public event AddGuest GuestRequest = delegate { return null;}
Im using resharper and the wise resharper( even it some times literaly eats the memory) made me the following suggestion
public delegate ContactCellInfo.Guest AddGuest();
public event AddGuest GuestRequest = () => null;
At my point of view the code using the delegate looks clearer. I am not against the Lamdba expression just would like to hear some advices on how and when to use them.
Lambda Expressions In C# Vs. .net?
Jan 20, 2010Functionally, is there any difference (apart from syntax onbviously) between lambda expressions in C# and VB.Net?EDIT: following up on CraigTP's answer: any references to the situation in .Net 4?EDIT: I'm asking because I'm used to C#, but for a next project the customer asks VB.Net. We're not a priori against that. We realize that most language constructs are supported in both languages. However, we're particularly fond of the way C# implements lambda expressions. We would like to have an overview of the differences with VB.Net
EDIT: accepted CraigTP's answer for pointing out what I currently consider the most important difference.
So to summarize: VB.Net 9 does not support multiline statements in a lambda expression, and a lambda must always return a value. Both of these issues are addressed in VB.Net 10
C# - .NET Async Lambda-expressions?
Apr 20, 2012Async Sub like this: Dim f As Func(Of Task) = Async Sub() End Sub Produces compiler error: error BC36670: Nested sub does not have a signature that is compatible with delegate 'System.Func(Of System.Threading.Tasks.Task)'.Equivalent C# code compiles fine:
Func<Task> f = async () => { };Rewriting Async Sub into Async Function make code works.
Why does Async Sub() is not convertible to delegate types with return value of type Task?
Converting Lambda Expressions To .net?
Jul 4, 2010how to convert this code to VB.net, can anybody help?
public static readonly DependencyProperty CommandProperty =
DependencyProperty.RegisterAttached(
"Command",
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Why Do Lambda Expressions In VB Differ From C#
Jul 19, 2011I just came across a bug in NHibernate which happens to already be raised: [url] I'm not sure if this applies to anything else other than enums but when using a Lambda from VB, it looks different to the same Lambda from C#.
C#:
Where(x => x.Status == EmployeeStatus.Active)
VB
Where(Function(x) x.Status = EmployeeStatus.Active)
They are the same as far as I'm aware? (My VB isn't great) If I put a break point on the same line of code, where the above code is passed into. In C# I get: On the same line when VB version is passed in, I get: Is this something I'm doing wrong? Is the result's the same, just displayed different between C#/VB?
Edit: Ok so they are displayed different, but they can't be the same because NHibernate cannot handle it. The C# version is handled perfectly fine by NHibernate, the VB version resolves in the following exception being thrown: [Code]
.net - MSBuild Fails On Lambda Expressions?
Jul 25, 2011I have an issue with building a project using the MSBuild (ver 4) from the command line when declaring lambda expression like this:
Private Sub Foo(ByVal s As String)
Dim WL = Sub(str As String)
If Not String.IsNullOrEmpty(str) Then[code]......
Background Info For Lambda Expressions?
Mar 6, 2009I'm trying to expand my programming horizons, and LINQ and Lambda Expressions have popped up as some apparently very important topics. As I began reading articles on Lambda Expressions, it appears that Lambda Expressions are built heavily on the concept of Delegates. As I began reading articles on Delegates, it appears that Delegates are built heavily on the concept of callback functions. As I began reading articles on callback functions, .[code]Can anyone out there give me a simple, clear, concise definition of callback functions? Do I need to learn C or C++ to fully understand these concepts? Maybe a better question is: What do I need to know to be able to understand Delegates (they've always somewhat mystified me) and LINQ/Lambda Expressions (I haven't looked into these too much, but they're mystifying, too)?I don't mind doing research, but google searches are giving me way too much information.
View 4 RepliesHow Are The Lambda Expressions Related To The Delegates
Jul 7, 2010what are delegates?How are the lambda expressions related to the delegates?
reading the msdn about the delegates is really confusing me ;so i need a start off from here before moving on to the msdn.
VS 2010 RemoveHandler With Lambda Expressions?
Jul 1, 2011To streamline code, I increasingly rely on lambda expressions. But I may have hit against the wall in the attempt of removing an event handler set by a lambda expression. This really eludes me. The code below shows two samples: Alt1 uses a plain lambda expression as delegate and works fine: the object size increases as the numeric control varies. However, the drawback is that the handler cannot be removed:
RemoveHandler Me.upDnScale.ValueChanged, Sub(sender As Object, e As Object) ScaleObject1(sender, e, objTgt)
According to this MSDN article, a variable should be used to set/remove lambda based handlers. Alt2 shows a couple of attempts, but none works.
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Lambda - Type Inferencing In Lamda Expressions?
Feb 22, 2010I have a type lets call it "MyType". I have a List(Of MyType). Here is what i'm doing: MyList.Sum(Function(x) x.MyFieldToTotal) "MyFieldToTotal" is a decimal. For the life of me i can't figure out why x above is an object rather than a type of "MyType". Shouldn't Type Inferencing be working in this case? Even in intellisense i get "selector as System.Func(Of MyType) as Decimal"
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Lambda Expressions With Multiple Search Criteria?
May 21, 2012Currently I am searching through my list to find Customers that match on Address.
I need to match on both address and city. How do I rewrite my lambda Expression to match both criteria?
CustomerList.FindAll(Function(c) c.Address = addressToMatch)
Remove Handler Setup By Lambda Expressions?
Jul 2, 2011How to remove a handler set up by a lambda expression? According to this MSDN article, lambda expression should be assigned to variables which should be used to define handler operators. So far, I have used lambda expessions w/o variables.
For instance, the following works:
Private Sub ScaleObjectInit1(ByVal objSrc As NumericUpDown, ByVal objTgt As FrameworkElement) ...
AddHandler Me.upDnScale.ValueChanged, Sub (sender As Object, e As Object) ScaleObject1 (sender, e, objTgt)
End Sub
Private Sub ScaleObject1(ByVal sender As Object, ByVal e As Object, ByVal objTgt As FrameworkElement)
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IDE :: Crash VS2010 IDE By Mixing Lambda Expressions With SyncLock?
Jun 30, 2011Can someone who is using a 64 bit machine help me pintpoint this crash to either the VS2010 IDE itself or one of the plugins I have installed?
It's the code fragment below. When I copy & paste it into the Main() function of a new VB.Net console app on my Win7 64 bit machine, the VS IDE crashes and dies onthe spot, every time I try it.
Doing exactly the same on a 32 bit XP machine, nothing abnormal happens.
The 64 bit machine does have some IDE plug-ins installed, the biggest of which is DevExpress (the free version), so i think either one of those or the fact that the IDE is running on 64 bit must be the culprit.
This is the code. The static variable can also be made a module-level variable, with the same result.
Linq - Order By Multiple Columns Using Lambda Expressions
Nov 16, 2009I'm still trying to get my head around the whole "Lambda Expressions" thing.
Can anyone here give me an example ordering by multiple columns using VB.Net and Linq-to-SQL using a lambda expression?
Here is my existing code, which returns an ordered list using a single-column to order the results:
Return _dbContext.WebCategories.OrderBy(Function(c As WebCategory) c.DisplayOrder).ToList
Note: The WebCategory object has a child WebPage object (based on a foreign key). I'd like to order by WebPage.DisplayOrder first, then by WebCategory.DisplayOrder.
I tried chaining the order bys, like below, and though it compiled and ran, it didn't seem to return the data in the order I wanted.
Return _dbContext.WebCategories.OrderBy(Function(c As WebCategory) c.DisplayOrder).OrderBy(Function(c As WebCategory) c.WebPage.DisplayOrder).ToList
VB Dynamic Run-Time Query With Linq And Lambda Expressions
Mar 16, 2009I have an untyped dataset returned from my WebService. The user wants to dynamically construct a query referencing tables and columns and specifying values to test for.I have looked at Lambda Expressions and the Expressions.Expression Namespace. I think these provide the answer I'm looking for, but I'm not certain how to go about contructing the linq expressions to extract the datarows I'm looking for.
I plan on limiting the result to one datatable that the query will result in and i"ll provide the joins from the user's constructs.For a simple example I have a DataTable with (n) rows called "Table", and in it there is a computed column called "b_IsActive" that has the expression "Convert(IsActive, 'System.Boolean')". The user wants to retrieve all rows in "Table" where field "b_IsActive" is true.
Book Recommendation With Good Lambda Expressions And LINQ Chapters?
May 20, 2009I'm looking for an advanced level VB.NET book which covers LINQ and Lambda Expressions.Generally I read C# .NET books due to lack of good VB.NET books when it comes to generic .NET Framework related subjects. However Lambda and LINQ is quite different in C# and VB.NET I'm looking for an advanced level VB.NET book on this subjec
View 1 RepliesLambda Coding - Basic Code Of Lambda With Explanation
Jun 21, 2011Im hearing about this, can someone explain it to me or please show some basic code of Lambda with explanation.
View 2 RepliesLambda Tutorial And Solving A Lambda-Function
Dec 14, 2009Is it possible to shorten the following function to a lambda expression?Or (to do the trick by myself) what is the best and most understandable for beginners tutorial for lambda in vb.net?[code]
View 2 RepliesLabel Only Counts Up To 9?
Apr 21, 2011am working on an app that generates 2 random numbers. When the numbers match it plays a sound. I'm trying to keep count of each time this accurs by using a label to hold the number each time it counts. It's working but when I use a label it only counts up to 9 then goes back to one and stays there. Here is a snippet of the code I wrote.
Public Class Form1
Public int As Integer = 0
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As
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.net - Group Duplicates With Counts?
May 6, 2011I need to go through a list of strings and count the number of duplicates and then print the string with the number of occurrences in one line to a file. Here is what I have but I need to only print the string once and its count.
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Array With Changing Counts
Jan 13, 2012I've used this method in the past and it's worked but I can't figure out what's different about the environment now that's stopping this from working.I have a string that I want to assign array values to. I dim it then I go to assign and I get "Object reference not set". [code] If I change it to the following it works but my UBound is too high for proceeding calculations and loops or too low to accept the total input I need it to take
View 4 RepliesKeeping Counts Win Form App. Has Run?
Apr 23, 2010using Vb net (2005) Wandering if it is possible to use AppSettings in this case: Keeping counts how many time my Win Form app. has run, could someone show me if this can be done
View 4 RepliesLinq2SQL Counts Getting Cached?
Sep 23, 2009I've got a very simple data structure. I'm using SQLExpress with Linq2SQL and vb.net
**ParentClass**
parentId
name
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Re-setting Dictionary Counts?
Dec 6, 2011I have set up text boxes to count how many times a certain item appears in my DataGridView but I want it to reset every time I click on a new index in a list box. How do I do it? Here is my code:
Dim myDict As New Dictionary(Of String, Interger)
Dim machineName As String
For Each row As DataGridView In grdTest.Rows
machineName = row.Cells("ProtosDataGridViewTextBoxColumn").Value.ToString()
If myDict.keys.Contains(machineName) Then
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Counts The Number Of Check Boxes In A Form?
Aug 20, 2009I need a code that counts the number of check boxes in a form this is my cod Public Class frmCount Dim counter As integer = 0 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
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Stopwatch - Counts Down To Zero From A Random Time Set When The App Loads
Jul 31, 2011I have a stopwatch that counts down to zero from a random time set when the app loads. Now what I want to do is when that timer runs out and someone clicks reset it again is random rather than the same time as before. My code is
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Timer - Counts A Number Up In Sequence In A Label
Feb 9, 2009I have a timer that basically counts a number up in sequence in a label. On the On Text Change sub for the label I have functions run when the label is at a specific number. Everything works fine, the only problem I have is I have information pulled from an ODBC link to a pervasive database every second, which slows down the program. I have several flash components that run so slowly because of the data update. Now I have tried both using a dataset and coding the query but it is still ver slow and processor intensive, I think its because the Pervasive ODBC link is somewhat slow. Is there a way to have my data pull timer run in the background so that it doesnt effect the performance of the rest of the program?
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Button It Lowers The Number In The Textbox And Then Counts Back Up?
Jun 10, 2011im a bit new on asking questions if you have a hard time reading this ill try and make t a bit clear for you but anyways.with this code in a button it lowers the number in the textbox and then counts back up
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Forms :: ListBox Counts Item And Pass To Textbox
Sep 12, 2010sd.JPG
How can I count the number of items in my listbox. Here is my codes:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
myListbox.Items.Add(txtText.Text & "")
End Sub
Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
txtTextListCount.Text = myListbox.Items.Count
End Sub