Is 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]
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Im hearing about this, can someone explain it to me or please show some basic code of Lambda with explanation.
View 2 RepliesI have this function that maps a IDataReader to a class. It is obviously written in C#. My co-worker wants to use the same method in his code, but he is writing in VB.net. Basically I am having difficulty rewriting this due to the Lambda expressions used in C#. He is running .Net 3.5.
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I have a problem with VB9 and Moq.I need to call a verify on a Sub. Like so:logger.Verify(Function(x) x.Log, Times.AtLeastOnce)And my logger looks like this:
Public Interface ILogger
Sub Log()
End Interface
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Should I be concerned about the performance of the Compile method here?[code]...
The reason I want the lambda expression is because I want that function to be able to get all the way through LINQ-to-SQL to be converted to SQL. The reason I want the direct version is because I have other code that I want to validate individual serial numbers before submitting changes. And I fear that GetValidSerialNumbers.Contains(serialNumber) will execute a more-complex-than-necesssary query.
I'm trying to sort a list of string, which (each item) consists of a word followed by a space, then a number. I want to sort first alphabetically by the word, then numerically by the number. I tried something like this:
wordList = wordList.OrderBy(Function(x, y) CStr(x.Split(" "c)(0)).CompareTo(CStr(y.Split(" "c)(0)))).ThenBy(CInt(x.Split(" "c)(1)).CompareTo(CInt(y.Split(" "c)(1))))
I am trying to pass a lambda function to Linq's orderby and cannot get it to work.
The relevant code is:
Dim myordering = Function(m) m.Count
If isAlphaOrder Then
myOrdering = Function(m) m.Key 'Order by Alphabet
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I have a lambda function that I can assign to a field and pass it to a sub routine, but cannot assign to a property. My field is defined as follows:
Public Delegate Sub SubDelegate()
Private pDeleteFunction As Func(Of BookCaseRow, SubDelegate)
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I'm trying to create a generic function to build a Linq expression from a list of Telerik grid filters. I'm trying to stay clear of dynamic Linq. Because I don't know the type that I'm building the expression for, I'm attempting to use reflection in the lambda functions to refer to a property, but after applying the fix suggested by @JaredPar I get the error, "The LINQ expression node type 'Invoke' is not supported in LINQ to Entities." Is there any way around this? here is my code:
Public Shared Function buildRadFilter(Of T)(ByVal filterExpression As List(Of GridFilterExpression)) As Expressions.Expression(Of Func(Of T, Boolean))
Dim returnPred = PredicateBuilder.True(Of T)()
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I have the below C# Lambda function and I need to convert it to a VB.Net code. I tried many times but I couldn't convert it the right way. [code]...
View 10 RepliesI'm trying to use a nested multi-line lambda Function in VB.NET and am getting an error. Here's what my code looks like:
cartItems = cartItems.Select(Function(ci) New With {.CartItem = ci, .Discount = discountItems.FirstOrDefault(Function(di) di.SKU = ci.SKU)})
.Select(Function(k)
If k.Discount Is Not Nothing Then
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I am dumb founded at this statement....maybe its just too many hours/days of doing C# to VB.Net conversion but i am drawing a blank on this conversion.
List<string> sColors = new List<string>(this.CustomPaletteValues.Split(','));
try {
List<Color> colors = sColors.ConvertAll<Color>(s => (Color)(new ColorConverter().ConvertFromString(s)));
What i have so far:
Dim colors As List(Of Color) = sColors.ConvertAll(Of Color)(....)
As you can see its the content of the lambda that i am hitting a brick wall with.
I 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.
I have been looking at certain tutorials on sharparchitecture and trying to no avail (the online convertors don't seem to be able to do this):
private Action<AutoMappingExpressions> GetSetup()
{
return c =>
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converting this to VB.NET
public void GetCustomers(Action<IEnumerable<Customer>> onSuccess, Action<Exception> onFail)
{
Manager.Customers.ExecuteAsync(op =>
{
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How would I translate this C# lambda expression into VB.NET ?query.ExecuteAsync(op => op.Results.ForEach(Employees.Add));
using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
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I have recreated the Predicatebuilder class in a seperate C# project and I'm trying to use it in a VB.NET project but I keep getting the following error: Overload resolution failed because no accessible 'Or' accepts this number of arguments.when I use it like so:
Dim predicate = PredicateBuilder.False(Of t_Quote)()
predicate = predicate.Or(Function(q) q.iQuoteType = iQuoteType)
The relivant project is referenced, I'm using the correct imports statement and it all compiles without any errors.
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Functionally, 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
In looking at Fuzzy Date Time Picker Control in C# .NET? Piotr Czaapla's answer to that question is exactly what I need. unfortunately, I'm a VB.NET guy and I'm not that familiar with lambda expresions, so my attempts to convert the code have resulted in hours of misplaced parenthesis and banging my head with a brick.
Any chance some bi-lingual wizard could convert the C# code to VB.net for me?
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Using lambda's in VB.Net results in no intellisense. Is this a bug with VS2010 or expected? Note that it works fine in C#
Return Array.TrueForAll(chequeColl, Function(x) x.Number <> "N") 'No intellisense Number does not appear
Return Array.TrueForAll(chequeColl, Function(x As MyClass) x.Number <> "N") 'Now casted intellisense appears
UPDATE: Here's an example
Public Class Cheque
Public Property Id As String
Public Property Status As Byte
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Async 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?
How should the following C# code be converted to VB.Net? I have tried several code converters and none produce correct results.
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I will probably sound like a bad developer here, but I am attempting to convert some code from the following page from C# to VB.NET:The code I am having trouble converting is from Step 4 of "Joining a Multicast Group" on the page, and here is the code with the comment lines removed:
private void Join()
{
_receiveBuffer = new byte[MAX_MESSAGE_SIZE];
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how to convert this code to VB.net, can anybody help?
public static readonly DependencyProperty CommandProperty =
DependencyProperty.RegisterAttached(
"Command",
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I want to implement this function:
Public Function GetFunc(Of TSource, TResult) _
selector As Expression(Of Func(Of TSource, TResult)) _
As Func(Of TSource, TResult)
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UPDATE:I have the following issue, it's a part of a function:
Dim obj As Object = value
For Each exp In expressions
If obj Is Nothing Then Return [default]
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Exception Details:
ArgumentException:Object of type 'System.Linq.Expressions.Expression`1 [System.Func`3[System.Char,System.Char,System.Char]]'cannot be converted to type 'System.Func`3[System.Char,System.Char,System.Char]'.
Is it possible to create anonymous delegates in vb.net version 8 or earlier? If so, could someone provide an example of the syntax?
View 2 RepliesIf been try to convert some code I have from VB.net to C# but I just cannot get it working!first is the vb code I'm only interested in the line that has the Lambda Expression for the C#[code]......
View 2 RepliesCurrently, I have code similar to this:
xxx, _
If(dr.Table.Columns.Contains("EnterpriseID"), dr.Field(Of Integer)("EnterpriseID"), -1), _
xxx
I would like to create a Lamdba expression something like the following (this doesn't work):
Dim xCol As Func(Of DataRow, String, Type, Object, Object) = _
Function(dr, x, t, dflt) _
If(dr.Table.Columns.Contains(x), dr.field(Of t)(x), dflt)
So that I can say something like:
xxx, _
xCol(dr, "EnterpriseID", GetType(System.Integer), -1), _
xxx
I have the following array
Dim items() = {
New CheckedListBoxItem("NYC", False),
New CheckedListBoxItem("CHI", False),
New CheckedListBoxItem("PHL", False),
New CheckedListBoxItem("SFO", False),
}
I am trying to query against it like this
Try
Dim item As CheckedListBoxItem = items.ToList().Where(Function(x) x.Value = "PHL")
MsgBox(item.Value)
Catch ex As Exception
MsgBox(ex.Message)
End Try
I am getting the error
Value cannot be null.
Parameter name: source
I also tried
Dim item As CheckedListBoxItem = items.FirstOrDefault(Function(x) x.Value.ToString() = "PHL")
I just need to query against the list to get an item and change it's checkedstate from false to true.
I 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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