VS 2010 Lambda Expression Confusion

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.


VS 2010 Struggling With OrderBy Lambda Expression?

Aug 24, 2011

I'm getting my feet wet with Lambda expressions and it's rather overwhelming.I have a UserPrincipal object called SelectedUser. I wish to get a sorted list of the user's groups This is what I have so far but when I include that code my application's form flashes a few times and closes! Also, what is the significance of the "r" in the "Return From r" statement?

Dim SortedGroups As PrincipalSearchResult(Of Principal) = GetSortedGroups(Me.SelectedUser.GetGroups())
Private Function GetSortedGroups(ByVal psp As PrincipalSearchResult(Of Principal)) As PrincipalSearchResult(Of Principal)
Return From r In psp.OrderBy(Function(t) t.Name)
End Function

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Delegate 'System.Threading.ThreadStart' Requires An 'AddressOf' Expression Or Lambda Expression As The Only Argument To Its Constructor?

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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C# - Lambda Expression: CS To .Net?

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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.net - Convert C# Lambda Expression To VB?

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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.Net Lambda Expression With No Intellisense?

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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Convert C# Lambda += Expression To VB?

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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Converting A C# Lambda Expression?

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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Extract The Lambda From An Expression?

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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Lambda Expression Not Working?

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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Lambda Expression Shorthand

Mar 30, 2010

Currently, I have code similar to this:

xxx, _
If(dr.Table.Columns.Contains("EnterpriseID"), dr.Field(Of Integer)("EnterpriseID"), -1), _

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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Trick Lambda Expression In VB

May 8, 2009

I know in VB Lambda expressions must return a value and can only have one statement. But in my case I just need to execute a Sub that does not return a value. Is there a way to trick it by somehow returning a dummy value yet still call my Sub? If possible what would the syntax be like?

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Using The Vb Equivilant Of The MAX Lambda Expression

Apr 7, 2011

I am having an issue using the vb equivilant of the MAX lambda expression. at foos.Max(function(x) x.id) when I try to intellisense the property ID VS will not show it. But when i run the example it works. Is there something I am doing which is wrong, an i am just lucky it runs? [Code]

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VB Lambda Expression For Sub Delegate?

Nov 29, 2010

There is the code:

Private Sub InsertItemInCache(Of T)(ByVal item As CachedItem(Of T), ByVal dependency As AggregateCacheDependency, _
ByVal key As String, ByVal updateCallBack As CacheItemUpdateCallback)


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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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Creating A Lambda Expression With Delegate?

Jul 16, 2010

I am Creating a Lambda Expression, but it' not getting me the write Out put : 

Public Class Form1
Delegate Function GetLastChar(ByVal S As String) As String
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load


I want Send a Name like "Arindam" and its return me "m", the last character.but in messagbox return value shows "fasle" I can't under stand why it's showing "False" instead of  "m", the last character.

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Delegate Not Working Instead Of Lambda Expression

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:
Dim reviewers As List(Of User) = users.Where(Function(u) u.DvRoleID = 2).ToList

Instead of using the lambda expression I can also write the function and call it as argument like this:
Public Function GetReviewer1(ByVal u As User) As Boolean
If u.DvRoleID = 2 Then
Return True
[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
If u.DvRoleID = 2 Then
[Code] .....
The compiler does not accept the crit delegate as argument.

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Getting Exports From Container In MEF (Lambda Expression)

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,
controllerName As String)


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Lambda Expression And Validity Of Delegates

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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Lambda Expression With Ternary Operator In VB?

Feb 26, 2010

Lambda expression with ternary operator in VB?

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Linq - Examples Of .NET Lambda Expression?

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:

modelBuilder.Entity(Of Model).HasKey(Function(item As Model) New With {item.PropertyA, item.PropertyB })

to map a composite primary key

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

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Use A Function Both Directly And As A Lambda Expression?

Apr 24, 2012

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.

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Use Lambda Expression Within ASP.NET MVC View Using Program?

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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VS 2008 - Convertion Of C# And Lambda Expression To .net

Feb 1, 2010

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

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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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C# - Use A Method Instead Of Lambda Expression With Extra Parameters?

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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Convert Lambda Expression In OrderBy Predicate From C#

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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Converting A Lambda Expression In Dispatcher.Invoke?

Mar 12, 2012

Simple question: How does this translate to VB.Net
Dispatcher.BeginInvoke(() => listening = false);

listening is a variable on the class (boolean). Converters online didn't nd what we've come up didn't compile:

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LINQ - Calculate Variance With Lambda Expression

Feb 3, 2011

I am trying to convert the following code for the variance calculation
public static double Variance(this IEnumerable<double> source){
double avg = source.Average();
double d = source.Aggregate(0.0,
(total, next) => total += Math.Pow(next - avg, 2));
return d / (source.Count() - 1);
Described on CodeProject into corresponded VB.NET lambda expression syntax, but I am stuck in the conversion of Aggregate function. How can I implement that code in VB.NET?

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Perform An Assignment Operation In A Lambda Expression?

Oct 25, 2010

I have a list of items and wish to set one of their properties to a certain value:

applist.ForEach(Function(x) x.PrePaidTypeID = CInt(DBEnums.PrePaidType.NoPrepay))

...but we think this just does a boolean comparison. Is there a way to force VB to assign the integer value rather than compare it?

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Set An Indexing Variable In Linq/Lambda Expression?

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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Method - Action(Of T) And Lambda - Error: 'Expression Does Not Procedure A Value'

Apr 22, 2009

Imports System.Reflection

Public Class Test


'This line indicates a compile error: 'Expression does not procedure a value':


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Using A Lambda Expression With ByRef Argument Gives Incompatible Signature Error

Mar 9, 2011

Why does this:Private [Function] As Func(Of Double, String) = Function(ByRef z As Double) z.ToString

gives the following error:Nested function does not have a signature that is compatible with delegate String)'.

While this:Private [Function] As Func(Of Double, String) = Function(ByVal z As Double) z.ToString

Does not? (The difference is ByRef/ByVal)

Furthermore, how might I implement such a thing?

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Can A LINQ Or A LAMBDA Expression Be Used To Count The 1's In A Binary String Or Char Array

Sep 15, 2010

Can a LINQ or a LAMBDA expression be used to count the 1's in a binary string ?For example, if I convert a number to its BINARY using.>>

Dim binaryString As String = Convert.ToString( numberVariable, 2 )

1) Without using a loop such as a FOR NEXT loop, can I count the number of 1's in the STRING using LINQ or a LAMBDA expression?

2) Can I get the indexes of where the 1's are at in a collection such as a LIST using LINQ or a LAMBDA expression?I know the syntax of some LINQ expressions, however, I don't know which method may be suitable.

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.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.

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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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