VS 2010 Optional And Named Parameters In An Attribute?
Sep 7, 2010
I have a custom Attribute class where the constructor takes one fixed parameter and two optional parameters. It is my understanding that one can supply one or more optional parameters by using 'named parameters' such as this:
Private Sub CallMethod()
Me.OptionalMethod(-1, z:=1)
End Sub
[code]....
Well, I thought, perhaps Attributes don't support named parameters. I know they can behave a little weird (they don't support all types in their arguments for example I think), so I thought little of it.But then... I noticed something else. If you take a look at my code of the attribute class again. Notice that I am using an attribute on that class as well... And what do you know: named parameters. Working just fine... The AttributeUsage attribute has the exact same configuration: one fixed parameter and two optional parameters. I seem to be able to call them using named parameters just fine, where I cannot call my own attribute constructor with named parameters...
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Aug 6, 2010
However, I am wondering if there are any workarounds or plans for incorporating this feature into VB.NET in the future?What I'd like to do:
Public Delegate Function Deserializer(Of T)(ByRef Buffer() As Byte, optional ByRef BufferPosition As Integer = 0) As T
'Implementation of a func that matches the delegate'
Class A
Public Function Deserialize(Byref Buffer() as Byte, optional Byref BufferPosition as integer = 0)
....
In the absence of specifying "optional" inside the actual delegate itself, it'd at least be nice to be able to do it in the function implementation only:
Public Delegate Function Deserializer(Of T)(ByRef Buffer() As Byte, ByRef BufferPosition As Integer) As T
'Implementation of a func that matches the delegate'
Class A
Public Function Deserialize(Byref Buffer() as Byte, optional Byref BufferPosition as integer = 0)
....
At least this second way, the functions for the delegate will always have a value mapped to each parameter, although some may come from the function side and not the calling side.
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Dec 21, 2010
I tried DbNull.Value but no luck. How do I assign a default value as null to a string parameter that is null in VB.NET? Its litte strange to see that VB does not have anything like plain null as most of the other languages do. Also what is the difference between null and DbNull and Nothing.
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Aug 9, 2011
What is the standard way to implement optional query parameters in a .NET WinForms application?In other words, only query on a field if the value of a corresponding control is not null.
EDIT: I use a FillBy method which calls a query in my Access database. In the TableAdapter query editor, I just used WHERE (field1 = ?) AND (field2 = ?) ... I just can't find the "hook" to bind form controls to the table adapter query parameters and so that if a form uses the default value to not query on it.
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Jan 21, 2011
Public Function Foo(ByRef a As AClass, _
Optional ByRef b As BClass = Nothing, _
Optional ByRef c As CClass = Nothing) As XClass
Error : Optional parameters must specify a default value.
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Jan 12, 2010
I would just like to know why. optional parameters cannot have structure types?
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Nov 3, 2010
I am interacting with VB code on a different tier, using a client-side c# program. The VB function signature looks like this:
Public Sub toggleExclusion( _
ByVal mouse As Double, _
ByVal study As Integer, _
[Code]....
I get an error saying no overloaded method of toggleExclusion takes 2 arguments?
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Mar 22, 2011
I have an object, called 'PERSON' This person object has a title, firstName & Surname property as well as many other which are at the moment irrelevant. It also has a read only property called Fullname which concatenates the two or three parameters mentioned above depending on an optional parameter 'withTitles' passed over when you call PERSON.FULLNAME
PERSON.FULLNAME(true) <- Will add titles if there are any
PERSON.FULLNAME(false) <- Will give the name without the title
Public ReadOnly Property FullName(Optional ByVal withTitle As Boolean = False) As String
[Code]...
I get an error: PERSON does not contain a property of 'FullName'. If I change this to any other property that does not take a parameter it works as expected. Now I'm guessing that the binding procedure can't handle optional or mandatory parameters for object properties, is this right? Is there a better way to do it? I thought about looping through the collection to add them manually but that kinda defeats the object of DataBinding!
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Apr 27, 2011
Is there an equivalent in Java to VB.NET's optional parameters?Also is it possible to switch on anything other than integers in Java?
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May 27, 2010
Is it possible to make Color variable parameters in custom classes Optional?Everytime I try, it gives me a "Constant expression required" error.[code]
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Oct 6, 2009
I was familiar with the optional parameters in vb 6 and it made sense given the capabilities of the language but why the heck does VB.Net support optional parameters when there is method overloading? Which one should I use and is there a difference? If there is a difference when should I use each one?
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Jan 12, 2010
Most of our code base is in VB.NET. I'm developing a project in C# that uses a lot of the assemblies from the VB.NET code.There are three relevant classes in VB.NET:
[Code]...
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Sep 16, 2010
I'm using a stored procedure to updateinsert data into a table using MERGE. One of the items being inserted is a VarBinary file. Now if I wish to add a new file it's just a case of using ReadAllBytes as below, to remove the file I pass DBNull. Now what if other fields are being updated but the file is not being changed? I want the field to remain untouched unless I'm replacing the file or deleting it as above. I cannot add the file via the parameter again as it may only exist in the database, unless I read it first and write it back which seems pointless. [Code]
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Feb 25, 2010
Now that C# supports named parameters, I was checking to see if it was implemented the same way VB did it, and found that there is a slight difference. Take for example a library function like this:
public static void Foo(string a, string b)
{
Console.WriteLine(string.Format("a: {0}, b: {1}", a, b));
}
[code].....
The way VB does it requires much fewer instruction calls, so is there any advantage to the way C# implements it? If you don't use the named parameters, C# produces the same thing as VB.
EDIT: Now that we've determined that the extra instructions go away in release mode, is there a particular reason for them to be present in debug mode? VB acts the same in both modes, and C# doesn't insert the extra instructions when calling the method normally without named parameters (including when you use optional parameters).
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Oct 20, 2011
I have a search function de build.We are using pure ASP.NET w VB.NET We have multiple DropDownLists and we're building a search query with whatever was selected in those DDLs. My question is, how can I handle the blank values (unselected dropdownlist values) with the SQL Query ? I'm using AND operators in the query so if anything is blank it'll fail the search. If the dropdownlist has no selected value, i don't want the value to be part of the search. It would be easy to code with just 2-3 parameters, but we're looking thru at least 10 items and doing a SWITCH CASE or multiple IFs would soon become mayhem.
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Apr 8, 2012
I have an ACE OleDb connection to an accdb file that�s working well but I�m mystified by something I recently discovered when using named parameters. Order of adding of parameters overrides the parameter names. I see in the MSDN that is states when in "Text" mode named parameters is not supported. My testing has proven this to be the case. The example below puts "Value 2 in Field1 and "Value 1" in Field2. In fact I could change @value2 to @blahblah and it works.
Dim command As New OleDb.OleDbCommand("INSERT INTO Results(Field1,Field2) Values(@value1,@value2)", con)
command.Parameters.AddWithValue("@value2, "Value 2")
command.Parameters.AddWithValue("@value1", "Value 1")
what is text mode and how do I change it and what other types are there? According to John McIlhinney�s earlier explanation things like date variables are added in a binary fashion including support for DBNull. So this is not "Text" so how am I sending binary data to a Db in Text mode? I�m just not getting why it supports names when it ignores them. Is it simply the case that there is no way to add parameters out of order in my case?If adding out of order is impossible should my command use some other syntax? I see other syntax that just uses question marks in the command dim for the Values section. EG "Values(?,?)".
Is there a way of adding parameters without names?In general I�d love to hear someone to explain this so I can understand the inner workings here a little better and have a little more confidence in what I�m doing here. I can fix my code to work but I feel like an idiot using parameter names that are ignored. I just know I�m doing something wrong even if it works.
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Oct 19, 2011
I just got upgraded from VB6.0 to VB2010. I'm trying to move some of my program functions over and I'm getting an error on the ones where I use optional... Public Function GetFolder(ByRef FTT As String, Optional InitFile As String)
I get the error at the end of the line, after the close par...the error is "optional parameters must specify a default value".
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Jan 8, 2012
am trying to add an extra optional parameter to a property but it gives this message.Specifiers valid only at the beginning of a declaration. Public ReadOnly Property ReadValue(ByVal Selection As String, ByVal Key As String,Optional Default as string="") As String
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Nov 27, 2011
here any algorithms/pseudocode for reading/parsing 3-column csv data and determining unique objects/attributes/values?
example data:
john,height,1.75
george,age,21
[Code]....
i have already implemented a solution of my own but it's too slow and i can't find any relevant literature on the internet.
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Nov 10, 2011
Possible Duplicate: Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive
I am using window xp and iis 5.1 to run the application.
error is occurred Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive.
[Code]...
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Jul 13, 2010
Hi, I'm trying to receive email in vb.net and I found a great tutorial on how to do it. However, I need a component named ADODB and Interop.MAPI.dll to do so. Where could I find either component?
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Nov 8, 2011
im asking for help on how to Make Folder and it name by current Date?
sample today is 11-08-2011
so program will create a folder name 11-08-2011 (Nov.08,2011)
and also creation of folder triggered by timer lets say Folder creation every 11pm daily.
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May 11, 2010
I'm trying to make a very simple audio tag editor. The idea is that the user can select as many audio files as he likes from a ListView, and a PropertyGrid will then display their tags + their values.When multiple files are selected, I want the property grid to display the values of the tags that all files have in common, and display empty values for tags that the files do not have in common.As an example, look at the properties list in your Visual Studio IDE when you select multiple controls (of the same type for this matter). Select a few Button controls, for example, and notice that the properties whose values are the same (often things like Font, ForeColor, etc) are displayed. Also notice that the values for properties that are not the same (Text, Name, etc) are empty.
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Mar 6, 2010
I am trying to have an optional Date value in one of my sub but since you cant set Date to nothing, this doesn't work. And i cant set it to the Date.minvalue inline.
Private Sub abc (ByVal A As String, Optional ByVal B As Date = Nothing)
End Sub
So, i went and set it to some date in the past.
Private Sub abc (ByVal A As String, Optional ByVal B As Date = #1/1/2001#)
End Sub
what would be the proper way to handle the default value for an optional Date?
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Feb 2, 2012
I get an error when I try to build my project.'SSLAccessFiltercannot' be used as an attribute because it does not inherit from 'System.Attribute'. [code]
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Apr 13, 2012
I have 2 applications that needs to talk to each others. After some research, I wanted to go with managed pipe (namespace system.io.pipes). The problem is, the client must send commands to the server but need to also wait for incoming message from the server at the same time. I tried to go asynchrone but it doesn't work.
[Code]...
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Jun 9, 2011
I've been linking to an external config file using <appSettings file="blah"> since VS 2003. I just created my first 2010 project, and I get no data from my file, nor any error. [edit]This functionality works as expected when I point to 3.5 framework.Another note, if I copy the other config to the debug directory and reference it by file name it works. When I use the UNC path it doesn't. The UNC path has worked for many of my past projects. Maybe it's a 4.0 security setting somewhere?
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Oct 16, 2011
I have a userControl that I made, and it was placed on a form with other controls.On the form I pass the values from the other controls to a Function inside the userControl, this then takes the values passed in and the values on the userControl to make and return an object.
The Problem is that when it gets down to '.GameOppScore = OppScore' it decrements .GameScore by 1 and then decrements .GameOppScore by 1. It does nothing to the passed in values or the value in the input text box.
It just randomly decides to -1, I walked through the code while running and couldn't find a reason why it would do that.
[Code]...
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Sep 9, 2011
I want my application to open a web page that has an iframe within it named "test_iframe". Now I want to obtain the text being displayed in test_iframe. How do I get this content (I dont need the HTML code, only text being displayed in that page). Also if the iframe is hidden, can I obtain the content in such a scenario also?
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Jun 17, 2012
Long story short I made a form in VB.Net project which involves lots of icons and images. My problem is when I build my project, and then go back to that form, suddenly errors showed up.
The errors says : "The type 'MyProject.MyResources.Resources' has no property named 'myicon'". Just to be clear, it worked fine before I did the build, and it happened to every single images I have on Resource.
When I chose "Ignore and Continue" all of the images I used are gone. I tried to googled it, some says to delete my .exe file on Application/Bin/Debug folder, which is working. But this issue has been some kind of an annoying one, since it happens again every single time I build.
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