I'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 RepliesI'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
I 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.
I am starting off in the .NET world and wanted to know what a great beginner book would be that would explain how to use asp.net, vb and SQL.
I hear "Learning Visual Basic" is a good series but wanted to see if there were anymore out there.
I am really interested in learning VB .net, but I don't really know where to start. Could anyone recommend a good book or website to start learning.
View 15 RepliesCan anyone recommend a good VB book that will teach functions, file IO, arrays, recursion etc. A lot of the ones I have looked at are very basic I started Sam teach yourself VB 2010 in 24hrs but a lot of it didn't relate to what we do in college.
View 2 RepliesIn my applications I use objects and classes, but when reading SO topics, I have the idea I don't use real OOP principles. For example, I never use inheritance or interfaces. Therefore, I am trying to learn proper OOP (in VB.NET), but I find some concepts quite hard to understand (even after reading a lot about the subjects on SO).So I'm trying to find a book or resource with good practical real-world examples. For instance, I kind of understand examples like using an interface for both Dog and Cat classes when using a EatFood method, but I find it hard to relate it to real-world cases.Ideally these books or resources should cover explanations about:
- when and why to use inheritance or interfaces or abstract classes
- when and why to use private, public, protected, virtual etc.
- best practices in dependency injection /inversion of control
- when to use aspect oriented programming
- using of constructors
- solid principles
- singletons
- encapsulation
Perhaps it's a mix of all kinds of concepts, but I think these are all related to OOP, please correct me if I'm wrong.I would prefer a book/resource with VB.NET examples, but this might be difficult?
I'm still a noobie whe it comes to VB.NET but I am going to be specifically orking/interacting with websites such as passing variables to textboxes, clicking on buttons, etc.
View 1 RepliesI 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.
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
I am a EE graduate from about a year and a half ago working in the semiconductor industry as a hardware/test engineer. I wan't to learn VB to do lab level data test and acquisition. I am learning this in my free time at work and home, and I would be using VB to talk with different electronic equipment through GBIP to source, measure, and record data. Anyone have any good ideas of a good book for such applications?? I know there are a ton of books and courses out there, but 99.9% of that information is not going to be needed for my industry application. I also took a few C classes in college, and I have some experience with labview so I am not a total noob to programming. So if anyone has a good book, or refferences that would be really appreciated.Also what version of VB would you recomend me learning?
View 4 RepliesCan anyone point me in the right direction for a good book or web site for Word and Excel Programming for VB. I'm not talking about VBA, I need to "work" with them from within my program not from within word or excel. I need to upgrade programs that were looking at Office 2000 and we're going to 07 or 10 not sure yet but figured I could at least get a bit of a jump on things.
View 2 RepliesI begain in 1971 learning TRS-80 Model III Basic language...later taught myself Lotus 1-2-3 and then DBase. Later, graduated to Visual Basic Stopped at VB 6.0. Now I need to move up to VB 2010...I have been programming for our company for sometime and use VB 6.0 as a front end for numerous Access DB applications.Can you recommend a good book (or books) out there that can help me with using VB 2010 as a frontend for Access?..just need the basics to be able to make connections, query the tables, return the data, update data, etc.
View 6 RepliesI'm new to VB but completly new. I've dabbled with it a bit before but mostly from copying and pasting code from online. Is there a good book that I can purchase that will show me the ropes of the basics?
View 5 RepliesAsync 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 to convert this code to VB.net, can anybody help?
public static readonly DependencyProperty CommandProperty =
DependencyProperty.RegisterAttached(
"Command",
[code]...
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:
[Code]...
I 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]
I 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]......
I'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 Replieswhat 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.
To 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.
[Code]...
I 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"
[Code]...
Currently 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)
How 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)
[Code] .....
Can 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.
I'm looking for a book that is pretty much A-Z for LINQ programming from Visual Basic. I am particularly interested in LINQ to SQL. I've found "Programming Microsoft LINQ in Microsoft .NET Framework 4" and while its description sounds interesting, there is no discussion on the book at all . Do any of you have any experience with this book? If so, what do you think of it?
View 3 RepliesThe pattern I'm trying to avoid is checking if a string (normally a control's text value) is null/empty, and if it is, comparing it using Contains to a field in my data. Obviously the field isn't hard-coded into my extension, neither is the object type.What I've got works perfectly in Linq to Objects, but I get the generic run-time error "LINQ to Entities does not recognize the method 'System.String Invoke(GenericQueryHelper.Customer)' method, and this method cannot be translated into a store expression." when using an entity framework model.
Here's what I have:
<System.Runtime.CompilerServices.Extension()>
Public Function CompareAndFilter(Of T)(source As System.Linq.IQueryable(Of T), expressionField As System.Linq.Expressions.Expression(Of System.Func(Of T, String)), compareTo As String)
[code]....
I want my usage to look something like this:
Dim results = repository.Customers.CompareAndFilter(Function(c) c.FirstName, searchText)
I do need to get this running against a SQL database really, as it is filtering results, so I don't want to be doing that in memory.
I converted the following query from C#:
src.Select((c, i) => src.Substring(i)).Count(sub => sub.StartsWith(target))
To the VB.NET query:
src.[Select](Function(c, i) src.Substring(i)).Count(Function([sub]) [sub].StartsWith(target))
Using Developer Fusion. I was just wondering why the VB.NET version has [] throughout.
I am learning MVC3 and transitioning to VB.NET from C# at the same time (Fun, I know). I am running through the MvcMusicStore sample for learning MVC3. All the samples are in C# so I am converting them to VB. I came across one piece of code that I was unable to directly convert and had to change slightly to get it to work.
why one way works and the other doesn't.
This does not work:
Dim albums = New List(Of Album)() From { _
New Album() With { _
.Title = "A Copland Celebration, Vol. I", _
[Code].....