Force A Compile-time Warning / When Using An Unassigned Local Variable?
Nov 15, 2010
Today I discovered that something I had assumed about VB.NET for many years was not true (worrying!). I assumed that a variable declared within a loop had a lifetime of the iteration it was declared in, but in fact it seems it has a lifetime of the whole procedure.[code]I had assumed an output of False, True, False, True but instead it is actually False, True, True, True..In C# the equivalent code would not compile as you would get a compile time error of Error "Use of unassigned local variable 'var1'".I realise there are many ways to fix this and that best practice would be to declare the variable outside of the loop and reset it at the beginning of every loop through.I find this behaviour so counter-intuitive to me that I would like at least a compile time warning in VB.NET when/if I do this. (I could also then set this on any projects I already have and get warning that would allow me to check that my assumptions aren't causing errors).Does anyone know how/if I can get this to generate a compile time warning in VB.NET? Am I the only one that finds this counter-intuitive?
Today I investigated a logical bug in our software and figured out that this is related to the way VB.NET thread variables inside a loop.Let's say I have the following code:
Dim numbers As New List(Of Integer) From {1, 2, 3, 4, 5} For Each number As Integer In numbers Dim isEven As Boolean
[code]....
The problem is that isEven is declared but not assigned.In this specific case, it would be correct to write dim isEven as Boolean = false but I haven't done this.In VB.NET, a variable that is declared inside a for loop keeps its value for the next itaration. This is by design: [URL]but this is also dangerous pitfall for programmers.
However, until now, I haven't been aware of this problem/behaviour. Until now.Most of our code base is C# anyway, which doesn't allow the use of an uninitialized variable, so there is no problem. But we have some legacy code that is written in VB.NET that we have to support. So the best thing would be to generate a warning or even an error in this specific case.But even with Option Explicit / Option Strict this does not generate a warning / an error.Is there a way make this a compile time error or maybe a way to check this with FxCop?
I'm using MSBuild (via NAnt) to compile a bunch of VB.NET assemblies. Because these assemblies depend on COM Interop, I need to guarantee that they run in 32-bit mode on 64 bit OS's. I can get the executable assemblies to compile to 32-bit by changing the project in Visual Studio, but I'd really like to be able to force all of the executables to be compiled to 32 bit mode on the build server.I've tried a number of command-line parameters to MSBuild with no luck:
is there any way to make the app load and compile local dll?
an exemple:
All process over visual studio 2010
i made an app on win7 that uses shell32.dll but the way that win7 compile his own interlog.shell32.dll it makes the app don't work in XP. But if after i finish the app on win7 send the code to a xp machine and set the shell32.dll on XP the app will work fine.
so... if there was a way to make the app, at his first load, do search from needed dll to compile them for his needs, it will was fantastic.
I have a Linq-to-SQL class diagram in my web application containing the two tables in my database (held in a DBPro database project in the same solution). All was working fine yesterday. I start doing some work tonight and note that the solution compiles fine in Visual Studio, but when I run the web app I get a compilation error:
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. Compiler Error Message: BC30002: Type 'FrostAlertDatabaseDataContext' is not defined.
1- Click run, and type the gpedit.msc, to start "Local Group Policy Editor". 2 -Expand "Computer Configuration" -> "Windows Settings" -> "Security Settings" -> "Local Policies" -> Then click "User Rights Assignment". 3- In the Policy window, Select "Force shutdown from a remote system", double click it, it will pop a properties window. 4- Click "Add user or group button", add a user and name it Guest.
I need to know if it's possible to manipulate and add the user or group programmatically. I'm using Visual Basic 2008.
I'm attempting to create a bound WPF control; when I add a local namespace to the UserControl, I get strange output from the compiler. The header of the UserControl follows, with the offending line highlighted.[code]When that line is present, the compiler generates the following in the output:[code]
This program is for advertising ads and prices are determined by which radiobutton is selected.This program uses objects created from a class . I am getting a waring message that Variable 'ad' is used before it has been assigned a value. A null reference exception could result at runtime. the warning is at ad.size = 225.So how do I get the variable filled before used if it depends on which radiobutton is checked? [code]
I am converting a VB6 program to VB express and am having a couple of problems. One of them is a problem with the variable "strEncTemp". I have the warning "Variable strEncTemp is used before it has been assigned a value", and I can't assign a value to this variable without creating issues. It also seems that a null value is being returned and the code produced by this routine is corrupt. This seems to be the last issue I have in converting the code. I tried setting it to 0 but it then shuts down the program with an error. This is the portion of code that has the warning and produces a null value. [Code]
1st label is "Clock" this pulls the time from the users current time zone/local time
2nd label is "UTCClock" Which would be UTC time
Now I have this for the first label: clock.Text = Format(TimeOfDay, "hh:mm:ss tt")
Which would give the users current time zone/local time. As for the UTC.. how would I add in for the UTC time from where the user is located at? I did some searches.. but couldnt find what I was looking for.. IM pretty sure its not as easy as getting the users current time zone/local time.. So im assuming that Theres a "bit more" code into getting UTC time..
I used .NET Framework 1.1 in C/S project before. Now I have updated the project to use .NET Framework 3.5 without modifying source code, but I have found that : the Remoted DateTime values can not be converted to the equivalent local time of a remote computer that is in a different time zone. In .NET Framework 1.1, the DateTime values can be converted automatically.
I have a program that reads a file with Pacific Daylight Time, I want users to see the time and date in their local environment.
At present I have in Australia a time difference of 18 hours, so I have a list box with -24 to +24 and currently set at 18, my code is elementary as long as I have moved past day one of the month it suits me personally, but I want to distribute my app, so I need something better.
I have a DataGridView which I AllowUserToAddRows behavior enabled. I want to be able to force that only one row be added at time, then if the user clicks the save button the row is inserted into the database, and then another row may be added if the insert was successful.
The reason I want to do this is to get the last inserted id and insert that information into another table.
Is there some clever way of getting the date and time of when the dll was built/compiled?
I'm using the assembly version numbering and reflection to retrieve and display this info when the app is deployed. But in some scenarios it would be more convenient to know when then dll was actually compiled rather than the auto incrementing version number. I don't think the modified date on the dll file itself is reliable due to the way the app is deployed.
Dim assemblies = AppDomain.CurrentDomain.GetAssemblies Dim assemblyName As String Dim assemblyVersion As String
I am having a problem while compiling one of my projects in vb.net. I have a solution consisting of multiple project,one of which is the exe. Now when i am trying to compile that project i get an error which states
Why if you pass an object as byVal into a method is it then treated as if it were byRef? I know you're only passing the reference across when you pass an object variable but why doesn't VB force you to decalre the header as byRef?
I want to have a bunch of different screens, yet I don't want to have to use 20 different forms (I'm pretty sure that's bad practice anyways), and I don't want to lay down all the controls at once in the designer because then things get messy. I had an idea of running a sub on startup that would dynamically generate all the controls I need with all the right coordinates and settings, and then dump al the ones needed for a specific screen into a Panel. Then I return an ArrayList of panels, and pull out the correct panel to attach to the form when I need that screen. The only problem is that my form will not have any implicit knowledge of its controls, so I'm assuming I wouldn't be able to use the WithEvents / Handles. keywords to declare handlers in the form class (which is what I'd rather do).
I've been building tools for ArcGIS. Part of ArcGIS is toolboxes which is basically a collection of tools bundled together. I know how to make toolboxes, but the code I have runs within Arc itself - ie. currently it only runs when you actually start Arc up and run a tool which makes the toolbox.
In theory the code should be able to run outside of Arc and ideally I want it to run at compile time. I know you can run executables as pre and post build events when building the installer so I was thinking I could make it build the toolbox as part of one of these. Catch is, the executable code would need to have access to the compiled files of my project (it needs a link to each tool to build the toolbox) so I can't make the executable in a seperate project. The current project is a class library. Is there a way to run code within my project when building the installer?
How can I get the type (it's name as a string) of:
1) an unassigned member?
2) the current class (I mean the one in scope) when no instance is available and without using a shared method?
EDIT: Come to think of I, I'm starting to think 1) is impossible.
EDIT: 2) may in fact never occur as such. Actually I meant the parent class of a nested class when no instance of the parent class is available (but an unassigned variable is) and without using a shared method of the parent class
Depending on a preprocessor directive, I want to set all properties in a class to EditorBrowsableAttribute.Never.
I thought about creating a custom attribute, derived from EditorBrowsableAttribute, but unfortunately that class is sealed.
I've had a look at ICustomTypeDescriptor, but in the GetProperties method, I can get hold of each property descriptor, but the attributes collection is readonly.
I have a component which hooks up with the paint event of assigned control and draws on its surface, Whenever i make any changes to the component i need to resize the form or control at design time in order to see the changes.
I want to ask if there is any other way to refresh the contents of a control at design time which forces it to redraw.
I may have a difficult question here. I am working on a Generic class that is meant to work specifically with Enum's. Right now, I get the type of the Generic on instantiation and make sure that it is an Enum and throw an exception if it is not. So:
[code] i get an app error when running the app, because i didn't set the ID.I was wondering if there's a way to make sure the programmer assigns all properties in the class,and fail at COMPILE TIME rather than have to catch the error at runtime...
We have a project for a client that is written in VB.NET. In one of the projects, we have about 100 modules, which are all VERY simple. They're extension methods that convert between object types. Here is a small snippet:
Public Module ScheduleExtensions <System.Runtime.CompilerServices.Extension()> _ Public Function ToServicesData(ByVal source As Schedule) As ScheduleServicesData
I have a code below to make collection that bind to a gridview able to sort by clicking on the column header. The problem here is "IPerson" is unknown at compile time. I want the delegate type able to decide by getting from gridview datasource.[code]....
I stumbled upon something i don't quite see the logic of. Let's ork with following piece of code:
For Each ds As DerivedScale In List If ds.ScaleID = scaleId Then ds.ScaleID = ds.ScaleID + scaleStep
[Code].....
This piece is written for 2 records to change place and change the sequence number (scaleid). The arrow indicates where the issue occurs. The item "ds" is replaced by the object 1 indexnumber higher/lower. This does however not effect that object in the List. So when i check, item ds isn't set.
However, when i look at ds.ScaleId = ds.ScaleID + scaleStep, this is reflected in the List.
So what I am wondering is: is "ds" acting like a local variable here, and can i only make changes to it's properties?
I'm writing a subneting calculator in VB.NET.I'm using the IDE SharpDevelop.Well my problem is I'm using a function to do some calculations and then to figure out the class of the IP addresses.Well I pass a variable from the subroutine, that is accessed when a button is clicked, to the function then the variable is passed back to the subroutine and then the variable is passed again to another function but when it reaches this second function it doesn't retain the value it was given in the first function.I'm not sure if I'm just passing the variable wrong or if this is how it works.I know I can make this work probably by using global variables but I'm not sure if this is proper. So my ultimate question is what is the difference between local and global variables besides just scope and should I try and use one more than the other.
I sort of understand why this is happening, but not entirely. I have a base class with a Shared (Static) variable, declared like so: Public Shared myVar As New MyObject(arg1, arg2)
In a method of a derived class, I set a local variable like so: Dim myLocalVar As MyObject = myVar
Now when I do something like myLocalVar.Property1 += value, the value in Property1 persists to the next call of that method! I suppose I get why it would be happening; myVar is being set by reference instead of by value, but I've never encountered anything like this before. Is there any way (other than my workaround which is to just create a new object using the property values of myVar) to create myLocalVar by value?
