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)
I'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 am doing a simple database project.I need to give the input in the database which is an access db from my input form and i have managed to do this part right.then i need to retrieve the details from the db using multiple search fields and show them in the datagrid view.I have 8 search fields(5 textboxes and 3 combo boxes). I also have included 4 other buttons which respectively clears the search boxes;clear the results of the gridview; show all results from the database;go to the input form and offcourse 1 search button.now all the buttons working fine except the search button. actually when i click on the search button if i include sql query for all the search fields only the first one works and also if i have clicked any other buttons before clicking the search button nothing happens, no result is shown and it happens the same if i search once and clicked any other buttons and come back to search, no result. I need to show the results in the gridview depending on the user input on those search criterias. user should be able to search in any combinations.I am using the below codings in my search form. the combo boxes are not bound.datagrid is bound to database though.
Public Class Paxsearchfrm
Private Sub Paxsearchfrm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'TODO: This line of code loads data into the 'LAFDataSet.Table1' table. You can move, or remove it, as needed.
End Sub
[code]....
[code]the main piece deals with the binding source filter. I've tried or/and. i tried to include that both codes in the string. i don't know what to do again i know you would recommend SQL but i don't know how to use that yet, so could you please recommend some bindingsourcefilter code to assist please. Its for a School project the search window looks like the attached picture
View 13 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
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 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]...
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 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'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 in a bit of a quandry. I am trying to build a simple search form where the user selects the column title and in puts the criteria then clicks the search button. This is the code I am using
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
details = ComboBox2.Text
'column name selected by user
specifics = TextBox1.Text
'criteria input by user
[Code]...
I have three controls on my form; Textbox1, cboCity, lstCity When something (lets say "a") is entered in the TextBox1; I want to get each and every item in combobox cboCity that starts with "a" and add them to listbox lstCity.
View 5 RepliesIn DataGridView I have three columns(year, month, day)
I wont first search dategridview by mounth, and the results search per day
I've got a form that populates a DataGridView from an excel file. How would I filter that DataGridView so only the search criteria are visible. I need to search through 2 columns by all rows. I'm not very good with datasources I guess and can't figure out what all I need to accomplish this. DataSets, DataViews, DataTables.
View 17 RepliesI'm using VB.NET with the MySQLConnector, I have an ID column with differents values, i.e:
101
102
201
202
203
302
304
305
306
I want to select all the values that start with "3" and then, select the MAX of them, in this case, "306"
I am building a real estate website. I have a table for properties (i.e. "houses"), a table for pictures, a table for features, etc. So each property's data comes from three, not only one table. I need to provide a function that retrieves requested property data depending on a search criteria, for example:
[Code]...
I need some guidance on the best way to proceed with searching a file content. I have a large file (see attachment) that is in text form, some of these files could be upto 50 times as big, therefore creating a huge file. These files contain information that is produced from another application and therefore I am unable to change the format of the file.
[Code]...
Check multiple expressions for null?I have this bit here[code]...
View 8 RepliesImports System.Text.RegularExpressions
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim t As Object
[code]....
I am trying to filter a list of (t) by multiple criteria. here is what i have:
[Code]....
I now want to filter this list by myObject's various properties. Heres the problem:
1. A user should be able to either filter on one specific custName or remove the filter for this property AND
2. A user should be able to either filter on one specific notificationDate or remove the filter for this propertyl AND
3. A user should be able to either filter on one specific materialType or remove the filter for this property
I know I can just write a lot of if..then but i'm looking for a more elegant solution.
I have a code to search through a listbox with mutiple search criteria. Here is the code:[code]When I search for something, how do I make sure I do not obtain 2 of the same results, If both criteria are found, or if all three are found?
View 4 Replies
