assuming v is a nullable, I'm wondering what are the implications / differences between these usages:
VB:
If v Is Nothing Then
If v.HasValue Then
C#:
if (v == null)
if (!v.HasValue)
i'm working on a system that upgrades a basic version to a proversion but i have a payment gateway . it generates a code in an SQL DB.now i have a form in VB that has a textbox and a button how can i let VB connect to my SQL DB receive the code and then check if that code is correct and if its correct download silence the pro file. from an url.
View 7 Repliestypeof(Nullable<>)
public static bool IsNullableType(Type t)
{
return t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>);
}
I was using this to check whether Lamda Expressioin parameters are nullable.
I have a code its for a pc game. Basicly it scans the chat using winapi calls. I'm trying to make when I type _place ammo (a vaild type of ammo that exists in game which is located inside dim vaildammo) I want it to make sure its a valid type of ammo to be placed. I used a for each statement but It doesn't seem to work.
[code]...
I am working on a business related program, so I need to know if system date is correct -synced- with remote server. How do you do that in vb .NET winforms?
P.S: In addition, is there any way to raise some event when system clock changed to prevent hacks? I don't want users to change local date after logging in their account.
How to validate IpAddress. I mean how to check whether the entered Ip is in correct format?
View 15 Repliesdoes somebody knows how to check for a valid IMEI?I have found a function to check on this page: url...But it returns false for valid IMEI's (f.e. 352972024585360).I can validate them online on this page:url...What is the correct way(in VB.Net) to check if a given IMEI is valid? [code]
View 1 RepliesWas wondering how to make it so users can log into the program and this would be much easier since the program allready connects to a database to add a username and password table which i have,how can i get it so when i click a button the program will check with the username specified if its in the data base and check the password of the given username returning a yes value if its right and conuing or exiting if its wrong?
View 4 RepliesI have a textbox where a user is supposed to enter a date. How can I check whether the entered date is in the correct date format?
Like this: 02/02/2008
not like this 022/22/-1
not like this 2009/02/02
not like this 02/Jun/2015
not like this 02/abc/2010
(I don't want to use DateTimePicker or MonthCalender).
EDIT 1 I tried it like this
Private Sub txtHireDate_Validated(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtHireDate.Validated
Dim dateString As String = txtHireDate.Text
Dim formats As String = "MM/dd/yyyy"
[code]....
But its showing some errors?
How do I check the correct OS version (xp, windows 7 etc)? I have seen an example like:-
Imports System.Environment.OSVersion
But this does not exist. All I have under environment is specialfolder.
How to check the word if both the given word pronunciation is correct Is there any function to check this using vb.net2.
View 6 RepliesPart of my assignment is to check if input to Group Number and Number of Units are correct input by making error handling exceptions...
I have to check the following:
a) group number is neither 501 nor 062
b) number of units are NOT numbers
c) number of units is NOT a positive number
So my first question is, am I checking correctly? 2nd question is, How do I make sure my Exceptions will pertain to their correct respective things (a, b, and c.. above)?
[Code]...
Is it correct to correct properties values on the fly? for example: (note the .ToLower)
Public Property X() As String
Get
Return _x.ToLower
End Get
[code]....
I accidently wrote some code today that was like this[code]...
I immediately noticed the issue, but I had already hit the run button. It compiled successfully, I ran it through to the section and it threw an exception.
You can't do this in C#, it gives a compile error "cannot convert from 'int?' to 'int'".
Is there an 'Option Explicit' type switch that I can turn on to ensure that this sort of error does not occur again?
I have created a basic query generator which allows a user to select the Select, WHERE and criteria attributes using a number of checkboxes.However i have got stuck. In the results form i have the following code
Private Sub DisplayRecord()
RichTextBox1.Text = ds.Tables("newResults").Rows(intCurrentRecord).Item(0)
RichTextBox2.Text = ds.Tables("newResults").Rows(intCurrentRecord).Item(1)
RichTextBox3.Text = ds.Tables("newResults").Rows(intCurrentRecord).Item(2)
[code]....
The program keeps on crashing if the user does not select the corresponding amount of display records from above for the amount of attributes they want for the SELECT part of the query in the intreface in form 1.
How would i go about making something where the number of SELECT attributes selected which are listed in a string create the correct number of textbox fields in the results form (form2)
I have beginner skills using VB (am using the Express edition to learn). I would like to know how to set up a conditional statement in a Windows Form (WF) app that would check if a specific command line has been passed by another separate app that launchesthe Windows Form app using command lines, and if not passed, then the Windows Form app would shut down (exit, close).So far, I can use:
For Each s As String In My.Application.CommandLineArgs
If s <> "xyz" Then
Me.Close()
[code]....
I have a bigger code block which I have recreated in this simpler example:
[Code]...
I have: Dim nVar1 As Long?Dim nVar2 As Long?Dim nVarSum As Long?nVar1 = Nothing nVar2 = 5 nVarSum = nVar1 + nVar2 I would prefer the result to end with nVarSum being 5, instead of Nothing. I understand if you add something to an unknown value, you will end up with "somthing + unknown" or x+5 will always equal "x+5" not "5" because you are still carrying around that unknown "x". However, how can I effectively treat an unknown or Nothing as a zero for the purposes of addition in this case?(What is basically happening is that the end user is sending us a data file, this code parses that file and then sums together about 15 fields. If the user leaves those fields blank instead of assigning a zero to them, I need to treat it as if it was a zero for this one addition operation, but all the rest of the code needs to continue seeing it as a Nothing value since the user did not ACTUALLY submit zero... they submitted blank or nothing)
View 3 RepliesCan Nullable Types be used in VB.NET? If so, is it possible to have a Nullable Integer that I can use with a field that accepts NULL in SQL Server?
View 4 RepliesI'm converting an Access VBA app to VB.NET. It has dates defined as variants or objects to handle null values. I thought this would be a great chance to use the Nullable type. But I can't get it to work. Either it is inappropriate for what I am trying to use it for, or I am doing it wrong. Anyone know how to use it? Reader is a SqlDataReader.
[Code]...
I was hoping I didn't have to put a lot of If .. Null statements throughtout the code, but that is my only option unless someone has any other idea.
I have the following line of code:
CType(IIf(CBool(product.IsDiscontinued Is Nothing Or product.IsDiscontinued = True), False, True), Boolean?)
What does the Boolean? mean at the end. I have seen it used on other data types as well.
I have a Nullable DateTimePicker but it lacks a vital property, that is to be able to change its ForeColor, anyone who has some suggestion on how can this be done? Or perhaps a free nullable DateTimePicker out there that supports changing of backcolor and forecolor?This is C# but it should not be different with .Net, and I prefer posting it here since there is more traffic here over the C# section.
using System;
using System.Collections.Generic;
using System.ComponentModel;[code].....
Okay, none of the previous questions I have seen with this error seem to apply in this situation.tEmp is a class that contains (among other things) two nullable date fields.[code]During a routine on my form, I am attempting to see if the following conditions are true[code]I get the above error (the title of question), but when I hover over the debugger, NextReview and InsuranceEligibleDate are both Nothing (which is correct for the employee I am looking at).I am using VB2010, and the Properties in the Employee class are using the new way of declaring Properties (i.e. no set/get)
View 4 Repliesdim str as nullable(of string) is this syntax incorrect?
View 1 RepliesC#'s 'as' keyword will let you do this: int? input = value as int? Here's what I would assume the vb.net equivalent would be: Dim input As Integer? = TryCast(value, Integer?) There's an intellisense error in the TryCast stating the operand must be a reference type but Integer? is a value type.
Intellisense on Nullable(Of Integer) says 'Represents an object whose underlying type is a value type that can also be assigned null like a reference type.' It seems C#'s 'as' handles this like a reference type where TryCast doesn't have this built in. In VB10 I was able to take advantage of the new CTypeDynamic function to do the casting. Conversion.CTypeDynamic Method
Dim input As Integer? = CTypeDynamic(Of Integer?)(value)
Or:
Dim input As Integer? = CTypeDynamic(Value, GetType(Integer?))
There's a cost here as CTypeDynamic examines the type at runtime.
My question is what is the elegant way to handle this without CTypeDynamic?
Dim input As Integer? = TryCast(value, Integer?)There's an intellisense error in the TryCast stating the operand must be a reference type but Integer? is a value type.Intellisense on Nullable(Of Integer) says 'Represents an object whose underlying type is a value type that can also be assigned null like a reference type.'It seems C#'s 'as' handles this like a reference type where TryCast doesn't have this built in.
View 1 RepliesI am a c#/asp.net developer and I am having to work on a VB/asp.net. I have two variables
Dim originalDate as DateTime?
Dim newDate as DateTime?
Both nullable datetimes, originalDate is a nullable date I am getting from the database and newDate time is set in code, I need to compare them, they can either both have dates, neither have dates or one have and one not.
I have a bit of code as follows:
if origEndDate = origEndDate then
When both origEndDate and origEndDate are "nothing" this statement is false (well when I run it in the watch window it comes back as nothing)!I don't understand why this is the case because I was under the impression doing an "=" compares the two values and as they are the same surely it should be true? What syntax should I be using as in C# I can do the above as so:
if (origEndDate == origEndDate) { }
and it will come back as true.
I've picked up some code from a colleague, and in one of his methods he has a boolean parameter: ByVal showProactiveChases As Boolean?. I had to look up the ? operator yesterday to see that it denotes a Nullable type. My question is, if I change it to: ByVal showProactiveChases As Nullable(Of Boolean), does the meaning remain the same? I think provided it doesn't change the meaning the second way is much more readable.
View 4 RepliesI am creating a setup project for my VB application. Everything seems to look fine. However when I tell it to build the solution I get the following error:Property 'keycode' is non-nullable. I have never seen this before in other setup projects and I can't find any help from MS.
View 8 RepliesIn the below sample code, I have tried to use Nullable(of T) for DateTime and I want to use it same of the Dimensions property which is List(of Dimension).
CODE: