Dynamically Change Variable Types?
May 10, 2010
I'm trying to make an application to do mathematical equations, but I also want to implement error checking. So that if someone doesn't put anything in one of the fields the output textbox will say "Error".
But the problem is that I already declared the variables I used as a numeric value, in my case decimal.
So, when I make an if statement that says if inputbox1="" then outputbox1="Error" it doesn't work.
I think that in order to get this to work I would have to have it setup so that the variable that is exported to the text property of outputbox1 could switch between being declared as a decimal or string value based on what the user put into the textboxes. But I'm not sure how to go about this. Declaring the variables inside the if/elseif statements won't work because the variables need to be declared before they are calculated within my if/elseif statements.
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Jun 18, 2011
I'm currently attempting to use a .NET WebBrowser to display help information (stored locally in html files) for an application I'm writing, however I'm experiencing two problems, both related to hyperlinks.
Firstly, I have a search function which returns the correct URL in the format file:\C:... I can copy and paste it into a browser, and it will navigate there. Yet clicking on the link within the control itself does nothing at all.
Secondly, the HTML files all contain relative paths to other HTML files. These of course do not work as I just end up with file:\C:help.html which gives me a 'webpage is unavailable.' But I can't think of a way to get it to work without parsing the HTML file and concatenating the path to the directory on to the front of the link.
Just to clarify, in the first problem I am dynamically building a search result page as the user types. The HTML contains several results similar to this (yes, it's unfinished, I'm just showing you the link part): [code] Now, when I click on that link in the control nothing happens, it doesn't give me a 'webpage is unavailable' or take me to the actual page. Saving the HTML, however, and opening it with Chrome, IE and Firefox works fine.In the second problem, I have a different help file for different sections, each containing relative links to several others. VB picks these up as direct paths, and attempts to go there from root, i.e file:\C:file.html. The only solution I can think of is to parse the file and use WebBrowser.Navigate(Path.Combine(pathToDirectory, nameOfHelpFile.html), which seems a lot more inefficient than it should be.
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Feb 8, 2011
i wonder if it's possible to define a variable/property of more than one type. Let's say i want a property TextWebControl that is a WebControl and also implements Web.UI.ITextControl(f.e. like a TextBox or Label). But i don't want to enforce that it is a TextBox or Label, but only one that inherits from WebControl and also implements ITextControl so that it also would work with controls added in future releases of .Net-Framework.
.Net-Framework 4.0
Edit: I have retagged the question and added VB.Net because it's my default language. Normally it's no problem for me to understand C# also, but i must admit that it's difficult to translate generic stuff to VB.Net without experiences and it's also better documentated in C# than in VB. So i would appreciate(and aceept) a working example of a VB.net generic type of ITextControl/WebControl.From Marc's answer i understand that i need a generic class. But how do i instantiate it in SomeClass? This won't compile:
Class SomeClass
Public Property info As InfoControl(Of WebControl, ITextControl)
End Class
Public Class InfoControl(Of T As {WebControl, ITextControl})
End Class
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Aug 18, 2009
I'm converted a VB6 project to vb.net using the convert tool.Now i have a few declares that included passing variables as "as any" which vb.net doesn't like and it seems you have to declare them as there correct type so i have the following,So i suppose , Long and Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory"(ByRef Destination As Any, ByRef Source As Any, ByVal Length As Integer)
and
Long again?
Private Declare Function CallNextHookEx Lib "user32" (ByVal hHook As Integer, ByVal nCode As Integer, ByVal wParam As Integer, ByRef lParam As Any) As Integer
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Sep 3, 2009
I am having some trouble with an array full of data which I am trying to process. The data has been picked out of an Excel spreadsheet and contains items such as phone numbers. The problem is that when I drop this array back into a spreadsheet, Excel being clever, decides that some of the phone numbers are numbers and removes the "+" from the front.[code]...
I know that adding a ' in front of the + will remedy this. What I need to do is find out which of the numbers in the array are actually numbers and which have spaces/characters in them. IS there a quick way of doing this without having to search through each individual character of each array position?
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Aug 8, 2009
I'm trying to wrap up a program I wrote in VB.NET and quick. I have a device that I am connected to through a serial port (COM4). It sent me 1056 binary bytes which I have stored in an array called newRecievedData. (see code below)
********** Start Code*********
Dim numberOfBytesToRead As Integer
numberOfBytesToRead = myComPort.BytesToRead
Dim newRecievedData(numberOfBytesToRead - 1) As Byte
[Code].....
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Mar 9, 2010
Is there any difference between the 2 methods below for calculating c ... specifically boxing/unboxing issues?
Dim a As Integer? = 10
Dim b As Integer? = Nothing
Dim c As Integer
' Method 1
[code]....
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Feb 1, 2011
I am working on a project where my class has to execute VB code provided by the user, to make it simple I am trying to recreate my own eval function, I am using the following code I found on the web to do this task.
Imports Microsoft.VisualBasic
Imports System
Imports System.Text
Imports System.CodeDom.Compiler
Imports System.Reflection
[Code] .....
The problem with code is that it can't access any variables or there values, so I have decided to get the variable names, there values types and there types dynamically and recreate them in the class that is being created dynamically. Any way to get the variable names there types and values in the current class or method, so that I can recreate them, and execute the user passed code, the user knows what variables are in the current class or method and there datatypes but he don't know there values as they may have changed, so he can't initialize them. Is there a way to do this, this code will be called in an asp.net page on page_load event, the code passed by the user is stored in the variable vbCode that is passed as a parameter.
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Dec 8, 2010
In a VB.NET Web Site, the User Types syntax coloring doesn't work. What are potential causes of this? It seems to not understand the difference between a "User Type" and an "Identifier."
Note: C# works as expected.
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Aug 18, 2010
I have a bunch of string variables, string1, string2, string3 etc.At the end of my program I want to write these strings to a file, but I don't want to have to laboriously type out string1, string2, string3 etc.
It would be much easier to use a loop to dynamically refer to (string & loopcounter), ie reference the variable by dynamically concatenating its name from a string and a number. Python can do this with eval(). How does VB do it? I can think of loads of examples where it'd be useful. Otherwise I have to type out all the different conditions and that's not efficient.
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May 9, 2012
I have searched online for a few hours to try to figure out how to do this, but nothing I found really makes sense, so could someone please tell me, in a simple way, how to do this?
Let's say I have a text box that the user fills out, named textbox1. And I have a combo box, named combobox1, which contains the choices A, B, C. And then I have a button named submit_button.
Each time that the user clicks submit_button, I would like to dynamically create a new variable. This variable should be named the same as textbox1.text, and should contain the value of combobox1.
For example, if the user types "blue" into textbox1, and chooses value "C" from combobox1, and then clicks submit_button... then the following variable should be dynamically created, like..Dim blue as String = "C"
And then, after that, if the user types "red" into textbox1, and chooses value "B" from combobox1, and then clicks submit_button... then another variable should be dynamically created, like...
Dim red as String = "B"
And each time the user submits new information into the textbox and combobox, a new variable should be created.Is it possible to have the program automatically create variables like this? If so, how?
My actual project is much more complicated than this, of course, so the above is just an example. But if I could figure out how to solve the problem in this example, I could figure out how to solve the entire project.
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Dec 21, 2011
I have started using the builder class to create my connection strings for the sole purpose of making more generic connectivity code. However, I am stumped on this issue. The MS eConnect product apparently expects to receive integrated security=SSPI in its connection string if you want to use integrated security, (vs Integrated Secturity=True). I thought I would just pass "Trusted_Connection"="SSPI" to the builder class.
as it turns out, the item for Integrated Security is boolean and despite what the documentation says, will not give me SSPI in my connection string. Has anybody else found this issue and is there a simple fix for it? as for now, I'll simply strip out the item and replace it in my string.
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Jun 7, 2012
I am using the AJAXToolkit Accordion control and dynamically adding panes to it based on a query of the database. For example:
Jane logs in and pulls up the page with the accordion on it. In the database she has five rows in the todo_list table. So, I need to dynamically generate five panes that contain the info. from the table...but if Joe logs in he may have only three rows, and Josh may have fifteen - so I can never know how many an individual will have beforehand.
So, I need some way to dynamically name the variables (or is there another way to do this). For example, here is some pseudo-code of what I'm trying to accomplish:
Dim i as integer
For each row in todo_list
Dim ap + i as New AccordionPane
Add some info from the row to the pane
Next
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Oct 6, 2011
I get the error
Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
in the following code..
Public Sub selCurrentManuf_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles selCurrentManuf.SelectedIndexChanged
End Sub
The drop list to go with it is the following...
<asp:DropDownList
OnSelectedIndexChanged="selCurrentManuf_SelectedIndexChanged"
selectedvalue='<%#Container.DataItem("c1_manufidcurrent")%>'
[code]....
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Aug 23, 2009
I created a lable to handle DateTime = Now, It works fine. but when I moved it inside a FormView I Get the following Message. Handles clause requires a WithEvents variable defined in the containing type or one of its base types?
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May 15, 2010
Is it possible to declare a variable and to choose it's appropriate type during runtime?
it should be something like this (of course, the last line does not work):
'Determine what type of variable is needed later
Dim myVariableType As System.Type = System.Type.GetType("System.String", True, True)
'Create variable with needed type
Dim myVariable As myVariableType ' Should be a string variable in this case
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Jul 6, 2010
How can I define the datatype of an variable dynamically. I read out data from a file. In the file it is specified, if the raw-data is interpreted as single, integer or .... So my idea is: To check, what datatype is in use and then declare an array with this datatype to store the data there.
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Nov 4, 2010
I want to set a variable in a class. But I want to dynamically choose which variable to set.
[Code]...
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May 5, 2010
is it possible to dynamically dimension a variable?in my case, i have a chart that has a varying number of series on it depending on the data extracted and in order to use those series, i have to dimension them manually before adding points to them, IE:
Dim series1 as New Series()
Dim series2 as New Series()
etc
etc
my series data is contained in a datatable, so i'll know the count required, but it will change at runtime, so obviously doing something like this won't work, but explains what i'm trying to do:
dim recordcount as integer = datatable.rows.count
for i = 1 to recordcount
dim "series"+recordcount.tostring as new series()
next
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Oct 19, 2010
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Click, Open.Click,Name.Click
SelectVid.ShowDialog()
End Sub
[code]....
I keep getting this error:
Error1'.' expected.
Error2Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
Error 2 is also error 3
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Dec 8, 2011
I am auto generating data grid and I am using check box in Data grid View,Now i am invoking check box state changed event but it produces the following error Handles clause requires a With Events variable defined in the containing type or one of its base types.
Here the code
Private Sub PRNT_CheckedChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles PRNT.CheckedChanged
Some Stuff.
End Sub
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Mar 25, 2010
I am in the processing of moving an app from VB to C# but some of the classes I will just be moving to VB dlls to access from the main C# app. In doing this I am trying to get the VB dlls to utilize the main C# class lib. In this C# lib I have an abstract clase called base process, it sets up a background worker and handles all the progress tracking, errors, and even reports an ETA. To use this in a derived class in C# you would just do this...
public class SomeLongProcess : Common.Multithreading.BaseProcess
{
public void start()
[code]....
The problem is that if I do the equivelant in VB I get an error "Handles clause requires a WithEvents variable defined in the containing type of one of its base types". Well I can't do a WithEvents in the base class because it is C# so..
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Aug 26, 2011
I am trying to follow this thread
[URL]
and I have it pretty close but have one error.
Quote:Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
That error is on both of these, in blue
Private Sub SpellChecker1_DeletedWord(ByVal sender As Object, ByVal e As NetSpell.SpellChecker.SpellingEventArgs) Handles SpellChecker1.DeletedWord
'save existing selecting
[code]....
I have added the reference, I have also added them to the toolbox. My dictionary is all set. What did I miss?
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Nov 22, 2011
i am getting errors on last two event handlers. what did i do wrong?
Error - Handles clause requires a WithEvents variable defined in the containing type or one of its base types.D:Shipping ApplicationShipping ApplicationForm1.vb75136Shipping Application
Error - 'PrintDocument1' is not declared. It may be inaccessible due to its protection level.D:Shipping ApplicationShipping ApplicationForm1.vb1119Shipping Application
[code]....
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Feb 4, 2009
So Im iterating through the properties of a class. For each property Im iterating through a datatable until I find a column name with the same name as the property.
No worries so far, here's the isse: Once I've found a match I want to set the class's property to the value in the datatable but I'm having difficulty referencing the property as it has to be done through a variable.
Code:
Dim per As New Person
Dim t As Type = per.GetType
For Each p As PropertyInfo In t.GetProperties
[Code].....
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May 11, 2009
Just upgraded a VS 2005 ASP.NET 2.0 website to VS 2008 ASP.NET 3.5. There was an error on the Sub Button_Click. It seemed to be a minor error, the website and the button worked just fine, as usual. What does the error mean?
Protected Sub btnDEreports_Click(ByVal
sender As
[code]...
Error 20 Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
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Feb 9, 2011
The code below works for the class that I hard coded "XCCustomers" in my RetrieveIDandName method where I use CType. However, I would like to be able to pass in various classes and property names to get the integer and string LIST returned. For example, in my code below, I would like to also pass in "XCEmployees" to my RetrieveIDandName method. I feel so close... I was hoping someone knew how to use CType where I can pass in the class name as a string variable.
Note, all the other examples I have seen and tried fail because we are using Option Strict On which disallows late binding. That is why I need to use CType.I also studied the "Activator.CreateInstance" code examples to try to get the class reference instance by string name but I was unable to get CType to work with that.When I use obj.GetType.Name or obj.GetType.FullName in place of the "XCCustomers" in CType(obj, XCCustomers)(i)I get the error "Type 'obj.GetType.Name' is not defined" or "Type 'obj.GetType.FullName' is not defined"
'+++++++++++++++++++++++++++++++
Imports DataLaasXC.Business
Imports DataLaasXC.Utilities
[code]....
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Jun 27, 2011
I am working on a site where the meta tags are set in a Masterpage in a section using runat="server". I can update the title, description, keywords, etc... through properties in the Masterpage code-behind, but how would I add or edit non-basic ones such as
I have tried the following, but it always returns 0 for the count.
Dim header As Web.UI.HtmlControls.HtmlHead
header = TryCast(Me.Master.FindControl("headerIdName"), Web.UI.HtmlControls.HtmlHead)
Dim count As Integer = header.Controls.Count
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Jun 1, 2011
I have close to 10,000 serverside pages, all of thse use the same stylesheet. I have created a new serverside page which is like a dynamic menu system to help find specific pages from the existing 10,000 pages quickly and easily.
The problem is, that if the serverside pages are accessed the old way using the old menu system, they should retain their old stylesheet. however, if they are accessed via the new menu system, they should use a new refreshed stylesheet.
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Mar 14, 2011
I'm trying to find a way to change the name of a text box if the name of the text box is first declared as such:[code]I tried the statement: Name = "SBox" & My. Settings. Row Countx but maybe this is wrong.To be very brief I'm trying to resolve this to under the following scenario:
1. Add a new text box to a tab page when user selects "add" button.
2. Each text box must be assigned a unique name
3. Data entered in each text box will be then be saved in my.settings (i.e., for each text box, there will be a corresponding variable/name to hold its text value)
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