Optional Method Parameter And String.Empty?
Apr 19, 2012
I have traditionally coded empty strings like this "", but for a couple of years now, I have been using String.Empty.I also normally never use optional parameters, but I'm refactoring a solution that's tied into my ERP, and I don't want to break anything. One of the changes was to add a parameter to proc, which pushes a new parameter into the method from which it is called. I coded it like this:
Optional BackReferenceID As String = String.Empty
But I got a syntax error "Constant expression is required." I guess String.Empty is non-deterministic??? Anyway, it seems like a bug. The workaround is of course to use double quotes.
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Jul 27, 2010
In my program i have it send an email and it send the email but after it sends i get this error "The parameter 'addresses' cannot be an empty string. Parameter name: addresses". I don't know why.
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Apr 9, 2009
I have a function that has an optional dictionary argument. Since it's optional, it needs a default value, and I'd like to set it to an empty dictionary instead of Nothing. How do I go about that?
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Jan 30, 2010
where i put the *'s i get the error "The parameter 'address' cannot be an empty string. Parameter name: address".
Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick
Dim mail As New MailMessage()
Dim SmtpServer As New SmtpClient
[code].....
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Mar 12, 2010
In VB.NET, it is entirely possible to pass an integer as a string parameter to a method without calling .ToString() - it's even possible to call .ToString without the ()'s. The code will run without a problem, VB will interpret the integer as a string without having been told to. In C#, these would cause compilation errors - you are required to call .ToString() and to call it correctly in that situation before it will compile. Is there a way to make the VB compilation process check for the same things as the C# compilation process? Would it be best practice in a mixed team to force this check?
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Mar 14, 2012
How can i create a optional parameter in C# as we create in VB.Net
Public Sub Demo(ByVal a As Integer,Optional ByVal b as integer=3)
End Sub
I want to declare this in C#
[code].....
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Sep 25, 2009
Is it possible to have an optional parameter of the type list?Ex.
Private Function TestFunction(Optional ByRef MyList As List(Of Double))
The real problem is giving the list a default value. When dimming a new list, you can use the code below to give it a starting value:
Dim MyList As New List(Of Double)(New Double() {1, 2, 3, 4, 5})
But even after trying many variations of the above code, I cannot get it to work as an optional parameter.
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Nov 1, 2010
Is there a way to pass an optional parameter to a webservice, instead of having to overload the method?If the webservice user is accessing the webservice directly, I want to do ActionA, if the user is accessing the webservice through my web interface, I want to do ActionA + ActionB.
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Nov 3, 2010
how can use color as an optional parameter in a sub/function?This doesn't work.
Code:
Public Sub WriteLog(ByVal sText As String, Optional ByVal lColor As Color = Color.Blue)
'Code
End Sub
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May 27, 2010
I have come across something confusing or potentially a bug in Visual Studio 2010 when defining an interface in my VB application: When defining an interface method with a default parameter of type Double, using the Double.NaN constant as the default value causes the code editor/intellisense/precompiler some issues.The following code underlines "INaNTest" and "INaNTest.DoSomething" claiming that 'DoSomething' cannot implement 'DoSomething' because there is no matching sub on interface 'INaNTest':
[code]...
where now "NaN" has been divorced from the "Double." prefix and underlined ('NaN' is not declared. It may be inaccessible due to its protection level.) The code editor has inserted invalid code again.Is there a correct solution to using Double.NaN as the default value for a method as defined on an interface, in VB.net, or is there a fundamental reason why this is impossible?
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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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Jul 28, 2010
I have a problem during defining a Sub routine in VB.Net. I am defining a sub routine which is as under
Private Sub ActivateControls(rdbutton as RadioButton, Optional txt as Textbox, Optional txt2 as Textbox)
End sub
When I call this sub routine It gives me the Error that Each Optional Parameter must specify a default value. So, Here I can't understand that what can be the default value of a textbox. What default value I can use here to remove this error.
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Sep 22, 2010
I think this is a pretty basic question, but I just want to clarify. If I have a variable with a null value, and pass it as a parameter that is optional, will the parameter get the null value, or the default value?
dim str As String = "foo"
dim obj As Object
//call 1
[code].....
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Nov 13, 2011
I tried the following, but i get the error
constant expression is required
Public Sub ExampleSub(ByVal Test as string,
Optional ByVal fromDate As System.Nullable(Of DateTime) = Date.Today)
'A Great sub!
[Code].....
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Apr 10, 2009
I am hardcoding an insert statement to a database, based on certain details a user enters into a windows form. The form has a few textbox and datetimepicker controls for the purpose. This form enters a single row in a single table in the database.The table has a few possible null columns defined, in those cases where the user does not have any data for those columns at that particular time.
I have to provide controls for passing data to those null columns nevertheless. In my case, I have two such columns that accept null values, and two corresponding controls - a textbox and a datetimepicker. The datetimepicker has a checkbox added to it so that if it is supposed to be null it doesn't pass the default current date value, and remains unchecked to explicitly specify that it is supposed to be null. By default it is unchecked.
My code is structured as follows:
Form1:
'the sub referenced here resides in a dll file in my dataaccesslayer code, and in my actual example is referenced properly.
'I have shortened the code here for simplicity
[code]....
Now it gives me an error whenever the code comes to the executenonquery(), and says something to the tune of "SqlDateTimeOverflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM."
I think the value of 'Nothing' from the subprocedure's paramter is not being assigned to the sqlcommand's parameter as a database NULL, which is what I need to pass to the database.I know instead of using optional parameters I can easily create overloaded subprocedures where one sub allows not passing values where the column(s) is supposed to null and other overloaded subs permit combinations of which column(s) are null or not. But it is simple as long as there is just one, or at the most two null columns in a table. If I have dozens of null values in a table that the user can choose to enter or not in a data entry form?
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Sep 18, 2009
My problem is this (apologies if this is a little long ... hang in there):I can define a function in VB.NET with optional parameters that wraps a SQL procedure:
Sub Test(OptionalByVal Arg1 As Integer _
Optional ByVal Arg2 As Integer _
Optional ByVal Arg3 As Integer
[code].....
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Jan 18, 2010
How can I create a nullable numeric optional parameter in VB.NET?
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Mar 3, 2010
I have a method written in VB.NET. It looks like this:
Shared Sub SomeMethod(ByVal Id As Guid,
Optional ByVal str1 As String = "foo",
Optional ByVal str2 As String = "")
I want to call this method from C# 3.0 and I want it to use its default arguments. I tried passing System.Reflection.Missing.Value, but I cannot cast it as String. Is there any way to do that?
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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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Mar 1, 2009
I have a method which requires a parameter to be passed in. I would like to use the Addhandler to call the method through a dynamically created button control's click event.
When I include () in the AddressOf, VS complains: 'AddressOf' operand must be the name of a method (without parentheses).
When I exclude the brackets, VS complains: Method '...' does not have a signature compatible with delegate...
My code:
CODE:
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Jun 12, 2011
As the title says I have a form with many databound textboxes. some of these boxes have data in them and some are empty. I need to add them altogether, so far all of the conversion methods I have tried err out when they run into an empty string, except Val, but then Val won't handle the string with a $ in it. I've tried decimal.parse which handles the $ but not the empty string. So I seem to be in circle that I can't get out of.
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Jun 28, 2010
This must've have been asked before but I couldn't locate it. In a mixed code project (VB and C#) we were debugging some old Visual Basic code where a statement as follows could be found:
If Request.Params("xxx") <> "" Then
'do something
I considered this a bug as Request.Params could be null, in which case the statement would've become false which wasn't the idea. So I thought. I just found out, -- probably for the tenth time and I will keep forgetting -- that the following two statements are not equal, while Nothing in VB should be equal to null in C# (thought I):
if(String.Empty == null) // always false
If String.Empty = Nothing Then ' always true
Should I dismiss this as a typical Microsoft backward compatibility effort, or should I consider this a huge error in the VB.NET compiler? Does anybody know the Microsoftean opinion on this oddity?
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Aug 2, 2011
I'm trying to use a variable that is simply a list of a list of strings.I've declared it as follows:
Dim iRows As New List(Of List(Of String))
Then I'm trying to pass it as a parameter to another method and I've defined the method as follows:
Public Sub Import(ByVal Rows As IList(Of IList(Of String)))
For Each Row As IList(Of String) In Rows
ImportRow(Row)[code]....
Unfortunately, when I try to run that code I get the following error where it tries to pass my variable to my method.
System.InvalidCastException was unhandled by user code
Message="Unable to cast object of type 'System.Collections.Generic.List1[System.Collections.Generic.List1[System.String]]' to type 'System.Collections.Generic.IList1[System.Collections.Generic.IList1[System.String]]'."
When I change the method definition to use the types rather than the interfaces as follows, it works.
Public Sub Import(ByVal Rows As List(Of List(Of String)))
For Each Row As IList(Of String) In Rows
ImportRow(Row)[code]....
So, is it not possible to use generics with interfaces in this way? It works fine as long as I'm not nesting them.
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Aug 11, 2010
I have a array of strings and I am looping through them, but the string might be empty so I am trying this:
[Code]...
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Dec 20, 2011
I am using Stanav's PdfManipulation2.AddImageToPage(..., Pages) for iTextSharp library (v5.1.3) and was not able to add the image to specific pages: e.g. to add to only page 1 and 3 of a five pages PDF
Dim Pages() As Integer
Pages = New Integer() {1, 3}
PdfManipulation2.AddImageToPage(..., Pages)
Calling AddImageToPage() with the the optional Pages parameter will add the image to all pages though.
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Mar 22, 2012
I want to pass an optional parameter to a function of type System.Drawing.Color. The problem I am having is that when I declare the function it says "Constant expression is required" but I have tried variations of the following, including integers, full qualified indentifiers, even old vbWhite constants to no avail.
[Code]...
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Feb 4, 2011
Is there a way to choose between different methods and pass one into another method ?
Sub conditionnal_binding(ByVal list_box_reference As ListBox, ByVal list_box_final As ListBox, _
ByVal dico_source As Dictionary(Of String, List(Of String)), _
ByVal my_methode As ??? )
' DO SOMETHING
End Sub
I wrote ??? because I don't know how to call another method inside a method.
I would like to choose between different "sub-methods". Here is how I would like to use my method :
conditionnal_binding(ListBox1, ListBox3, HTML.dico_basic_attribut, best_method)
conditionnal_binding(ListBox1, ListBox3, HTML.dico_basic_attribut, some_method)
conditionnal_binding(ListBox1, ListBox3, HTML.dico_basic_attribut, another_method)
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Aug 13, 2011
I'm trying to code a class of RandomNumber. One of the class methods needs to populate a "List (Of RandomNumber)" ... which was passed as a parameter to the method ... with 10 random numbers between 1 and 50. DEAD SIMPLE :)
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Mar 30, 2010
I have a a method drawPaper(g, rect,.....).This drawPaper method is called on from another method (PrintPaper method) with the parameters passed on as (e.graphics, rect, .....) i.e drawpaper (e.graphics, rect, .....) why is the method called with the e.graphics argument not with g as per the method.
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Mar 19, 2009
Given the following classes, how can i intercept Class1.SampleMethod's Value from SampleAttribute?[code]...
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