.net - "Using The Iteration Variable In A Lambda Expression May Have Unexpected Results"

Jun 27, 2012

Edit: Here is a much more simpler example of this issue (i've deleted my original question):

Dim numbers1 As New List(Of Int32)({1, 2, 3})
Dim numbers2 As New List(Of Int32)({3, 4, 5})
For Each n1 In numbers1
' no warning '
Dim contains = numbers2.Contains(n1)


The local variable number1 is redundant and makes the code less readable as @Meta-Knight already has emphasized. Note: All three ways are safe and give the correct result.


Get: "iteration Variable In A Lambda Expression May Have Unexpected Results"

Mar 1, 2012

Possible Duplicate:Why is it bad to use a iteration variable in a lambda expression.why do I get: "iteration variable in a lambda expression may have unexpected results"? Suppose I have the following code:


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C# - Using Iteration Variable In A Lambda Expression?

Feb 16, 2012

[URL]..Module Module1


It says the result will always be 5 namely the final value of i. How come?

They don't put the iteration variable in the "closure"?

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How To Suppress VB's "Iteration Variable Shouldn't Been Used In Lambda Expression"?

Sep 30, 2010

I'm working with LINQ in VB.NET and sometimes I get to a query like

For i = 0 To 10
Dim num = (From n In numbers Where n Mod i = 0 Select n).First()


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Apr 16, 2010

I have a lambda expression that builds a list ofanonymous types. I would like to include a property in the anonymous type that is a counter. So the first entry is 1, second 2, third 3, and so on.I thought I recallenyone know the syntax for defining an indexing variable as part of a Linq query or lambda expression?

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Apr 15, 2012

I'm flummoxed I'm using VB.Net, Linq, and a DataContext. My DataContext contains a table 'transactions'.

I first declare an IQueryable(Of transaction) and assign it to nothing. I build a predicate in a foreach loop and use a transactions.Where(predicate) to assign the IQueryable a value. If I do an IQueryable.ToList(), I get a number of items in the collection.

However, on the next iteration of the loop, the IQueryable.ToList() gives me 0 items.This is driving me crazy. I tried to use the LINQ to SQL Debug Visualizer with VS2010, (I recompiled the 2008 version with the new reference) but no dice - I can't see the SQl generated or what's inside the IQueryable.


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Jan 23, 2010

I got this Error. below is my code.

GenerateTheList is function.Need help
Private Sub buttGenerate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles buttGenerate.Click
Dim thread1 As New Thread(New ThreadStart(GenerateTheList))
End Sub

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AddressOf' Expression Or Lambda Expression

Feb 22, 2009

From this code


If I put New Action(AddressOf PrivateMesage), then I get the following error: Bounds can be specified only for the top-level array when initializing an array of arrays. on the following code


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Mar 10, 2011

Just when I was thinking that I had Linq To Xml sussed I'm faced with yet another error! I think if I was to understand the linq search process in general better I might have more success, so any good links regarding that are also welcome. To my problem however; using the code below:


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Sep 4, 2007

I am writing an app in VB2005 that makes a call to my cars ECU. It sends ok but during the DataReceived event I am getting an unusual result.I am trying to find out how many bytes are in the buffer so I can set up an array to write the data to so I have used the following.

intBTR = _Port.BytesToRead
_Port.Read(bytIncoming, 0, intBTR -1)


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Feb 20, 2009

Consider the following snippet:
Dim Arext() = {"*.ttf","*.ttc"}
For Each foundFile In FileSystem.GetFiles(srcdir, SearchOption.SearchTopLevelOnly, arExt)


The unexpected result is that not all the files specified in arext() are returned by this code. Running the same code twice on the same subset of files does NOT produce consistent results.I'm seeing, probably, 90% of the files with the other 10% not being included?

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Aug 24, 2011

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.

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Mar 23, 2012

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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Mar 9, 2011

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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Feb 15, 2011

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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Dec 15, 2011

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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Aug 9, 2010

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)


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]


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]'.

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Jun 12, 2012

If 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]......

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Mar 30, 2010

Currently, I have code similar to this:

xxx, _
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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), _

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May 8, 2009

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Apr 7, 2011

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Nov 29, 2010

There is the code:

Private Sub InsertItemInCache(Of T)(ByVal item As CachedItem(Of T), ByVal dependency As AggregateCacheDependency, _
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Jan 23, 2012

Is the warning I am receiving about using the iteration variable in this line a concern.

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Jul 16, 2010

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Public Class Form1
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May 14, 2010

I am having a generic ListOf-collection holding the self-created User-object, I can filter for users by using lambda-expression like this:
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Instead of using the lambda expression I can also write the function and call it as argument like this:
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If u.DvRoleID = 2 Then
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[Code] .....

Now the question: why can't I create a delegate having the same signature as the GetReviewer1 function and use the delegate as argument inside the where-clause like this:
Delegate Function Criteria(ByVal u As User) As Boolean
Public Function GetReviewer1(ByVal u As User) As Boolean
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Jun 22, 2012

I am trying to see if the controller class name is the name of the controller name passed in. I think my lambda expression is wrong and that is why it isn't working properly. I am passing in the correct controller names, but the export variable is always null.

Public Function CreateController(requestContext As System.Web.Routing.RequestContext,
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May 6, 2010

In MSDN documentation defination about lambda expression is "A lambda expression is a function or subroutine without a name that can be used wherever a delegate is valid ". Here validity of delegate is necessery only when we are passing lambda expression as an argument to a method.


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Feb 26, 2010

Lambda expression with ternary operator in VB?

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Feb 3, 2011

Where can I find complex LINQ examples made using VB.NET Lambda Expression syntax?During my searches I always found 101 LINQ Samples but they use the other notation and for me is not always clear how to transform that code into a lambda expression.

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Make Lambda Expression Dynamically?

Jul 13, 2011

In Entity Framework I usually do something like:

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I need to write a generic function like[code]....

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Apr 24, 2012

Should I be concerned about the performance of the Compile method here?[code]...

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Oct 28, 2009

With ASP.NET MVC 1.0, .NET 3.5 and C# you can easily pass a method a lambda expression that will do a "Response.Write" some content when it's executed within the method[code]...

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Feb 1, 2010

is there any perfect tool of converting C# and lambda expressions into vb.net code.

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Sep 21, 2011

I've been wondering about lambda expressions for a while now.Consider the following code..[code]But in the lambda expression I have access to all Sub Main's variables.

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Oct 20, 2009

x = 4.2 - 0.1
vb.net gives 4.1000000000000005
python gives 4.1000000000000005
Excel gives 4.1
Google calc gives 4.1

What is the reason this happens?

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C# - Convert This Anonymous Method / Lambda Expression Across?

Feb 23, 2010

How would you convert this to VB (using .NET 4.0 / VS2010) ?

bw.DoWork += (o, args) =>
Code Here

I thought maybe like this:

AddHandler bw.DoWork,
Function(o, args)[code]....

But it says Function does not return a value on all code paths.

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'ByRef' Parameter '<parametername>' Cannot Be Used In A Lambda Expression?

Feb 12, 2011

I'm using SharpZipLib to compress files. The library is wrapped in a plugin interface, in a separate DLL. I pass the plugin dll a ByRef parameter to keep track of the compression progress.SharpZipLib, while compressing, will periodically call a delegate sub passed when launching the compression. I can't figure out how to update the ByRef parameter when the delegate is called. If I try to assign the ByRef variable in the body of a lamba expression, I get a 'ByRef' parameter '<parametername>' cannot be used in a lambda expression error.


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Jan 27, 2012

I have an inline lambda expression that I would like to use throughout my application. I just can't seem to find a reference on how to do this with more parameters than the element being tested. Here is a quick example of what I currently have.

Private Sub Test()
Dim List As New List(Of String) From {"Joe", "Ken", "Bob", "John"}
Dim Search As String = "*Jo*"


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C# - Wrap Code In A Lambda Expression Using A BackgroundWorker?

Jun 24, 2011

Consider the following C# code:

private void SomeMethod()
IsBusy = true;
var bg = new BackgroundWorker();
bg.DoWork += (sender, e) =>


However, I'd like to be able to implement a method like SomeMethod from the C# example in VB.net. Likely this means wrapping the Backgroundworker in another class (which is something I want to do for dependency injection and unit testing anyway).

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Apr 24, 2012

I've got the following to sort entities by their job position. The desired order ist defined in another array. In C# this code works:[code]However I will have to convert this to VB.net. I read the equivalent would be something like the following:[code]This does not compile, gives me "Expression expected" right after the Function(x). What am I doing wrong?

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