I am new to VB.Net and I'm a little confused why this line happened to be valid in VB:
DataGridView1.DataSource = ds.Tables("Customerslist")
DataSource is of type Object while Tables("Customerslist") is of type DataTable. How will I know what types of objects can be assigned to the Datasource property?
I am having a problem with objects and arrays of objects. Basically obj_stored holds how many objects I have stored in my text file, in this case t shirts. line(y) is an array that holds each line that has been read from the text file. I then use this to assign values to my array objects properties. For example I know the first line is the color of the first t shirt, second size, third price etc. Then I know the next line will be the color of a new t shirt. There are 6 t shirts in the file.
Dim t_shirt(5) As Clothing.t_shirt
Dim t_shirt_purchased As New Clothing.t_shirt
For x = 0 To obj_stored
t_shirt(x) = Clothing
t_shirt(x).color = line(y)
y = y + 1
t_shirt(x).size = line(y)
y = y + 1
t_shirt(x).price = line(y)
y = y + 1
Next
MsgBox (t_shirt(4).size)
My problem is it seems to be resetting these values after it has finished. Im creating the object each time and assigning values to it's properties but when it's finished it all resets and says 'Object reference not set to an instance of an object'. I'm new to OOP and was wondering what sort of approach i would take to doing this, if the one i am taking is wrong.
So I am aiming to:
Read everything in from the text file.
Create new instances of the objects depending on how many t shirts are stored, (5 t shirts = 5 objects)
Assign the values to my objects properties.
Im doing the same thing as him but in vb express 2008 what i have is a checklist box of 10 toppings, all of which can be selected, (no max or min) to put on a pizza, and i have 3 radio buttons grouped together for pizza size (S, M, L) i cant figure out how to give them vaules in which(for sake of demonstration) s=$5 m=$7 l=$9 and each topping is $0.25 then make them add up to an order total in a msg box or something like that
View 2 Repliesi saw jim example in the codebank and i added the percent progress parameter to report progress method (to change the progress bar value)this is jim example:-
vb.net
Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, _
ByVal e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
[code]....
I am getting this error, Not sure why it is happening "Error The SqlParameterCollection only accepts non-null SqlParameter type objects, not Int32 objects."I have tried with all sorts of possibilties, now try to enter default data as dummy data,
Using connection As New SqlConnection
connection.ConnectionString = ConfigurationManager.ConnectionStrings("DentalDeviceConnectionString").ConnectionString
connection.Open()[code].....
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Using conn As New SqlConnection("Database=Clinic_Management_System;Data Source=.SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|Clinic Management System.mdf")
Dim cmdRecord As SqlCommand
[code]....
I have a structure that contains another structure. The inner structure is nullable. Now wht I do is something like the following. I create a new instance of the inner structure, set the member variables and assign the whole structure to the inner structure of the parent. But it is giving an error. The assignment is not successful. If I try to peek into the structure in the watch window, it says "property evaluation failed" for the HasValue and Value properties.
Dim testData As List(Of TestData) = Nothing
Dim testData_List1 As New TestData
With testData_List1.commonTestParam
[Code].....
I want to assign a Value to a Variable of Decimal Type to do a calculation, but when I enter the decimal value (a 28 digits to the right of the decimal point - very long numbers) it gets altered. I give below what I was doing:
Dim MyNumber As Decimal = 0.7777777777777777777777777774
But as soon as I finish typing the number, it becomes 0.77777777777777779 and appears as,
Dim MyNumber As Decimal = 0.77777777777777779
And, when the cursor is kept over the altered number it shows as "Double, Represents a Double - precision floating-point number." How can I get the value I wanted to stay without getting changed? I was able to get this long Decimal value as the result of a calculation and get that appears in a text box in the same program. Is there anything I should change in the "Visual Studio 2008" to get this ?
When using the If operator [URL] to assign a value to a System.Nullable object, if the result is Nothing (null), then 0 is assigned to the object. Example: 'Expected value is null (Nothing). Actual value assigned is 0. Dim x As System.Nullable(Of Integer) = If(1 = 0, 1, Nothing) If x is a nullable type, why is it being assigned the default integer type of 0. Shouldn't it receive a value of null?
View 2 Replies.Net 4.0
Option Strict On
Option Explicit On
This works perfectly:
Dim N As BigInteger
N = 28 'Put whatever value you want in for N.
Write((BigInteger.Log(N) / BigInteger.Log(2) + 1) / 2)
This does not work:
Dim Result As BigInteger = (BigInteger.Log(N) / BigInteger.Log(2) + 1) / 2
This gives an error during the build (despite the variable being declared as a BigInteger and the operation working perfectly well when I am not assigning it to a variable, it tells me I can't convert a Double to a BigInteger) and I have to do this:
Dim Result As BigInteger = CType((((BigInteger.Log(N) / BigInteger.Log(2)) + 1) / 2), BigInteger)
This if course gives a different, that is, incorrect result.'This doesn't work either.
Dim Result As BigInteger = BigInteger.Log(N)
'I can do this:
Dim ResultString As String = BigInteger.Log(N).ToString
'But then parsing the string fails
[code]....
I've created a class that inherits from Dictionary(Of TKey, TValue) called KeyCopyDictionary(Of TKey, TValue). I'm now trying to use a pre-existing function which returns a Dictionary(Of String, String) and assigning it to a variable of type KeyCopyDictionary(Of String, String). I'm getting an invalid cast exception. Is it not possible to assign a variable of a parent type to a variable of its child type? I've tried DirectCast and CType to no avail on this...
View 5 RepliesHow find an object's type when it is a subclass of another object and I only know the string value of the object's type's name. I created the following classes:
HTML
Public Class word
End Class
Public Class noun
Inherits word
[Code] .....
Then, in my code I create a new properNoun and check to see if it is a properNoun, noun or word:
HTML
Private Sub checkTypes()
Dim pn As New properNoun
MsgBox("Is a properNoun: :" & TypeOf pn Is properNoun) 'TRUE
MsgBox("Is a noun: :" & TypeOf pn Is noun) 'TRUE
[Code] .....
I correctly see that pn is a properNoun, a noun and a word. The problem is, using 'GetType' to check pn against a string value, I can only see that pn is a properNoun, not that its parent classes are noun and word. Is there a way to check pn against the string value "noun" or "word" and get back a positive result, indicating that pn is indeed a noun and a word as well as a properNoun?
I created a Class which inherits Combobox and the listview is added . Now what I need is once the user click listview, the listview has to close and the clicked item has to added with combobox text. simply can say combobox1.text = listview.item(0).textFor closing & displaying the listview I need to handle the events. For
My Codings :========Public Class Combu_lstviewInherits ComboBoxPrivate treeViewHost As ToolStripControlHostPrivate Shadows dropdown As ToolStripDropDownPublic mylistview As New ListView
Public Sub New()mylistview.BorderStyle = BorderStyle.Nonemylistview.View = View.Detailsmylistview.HeaderStyle =
[code].....
Is there a way to attach a Sub or Function to an event of many controls at once?For instance, to clear a bound combobox I use this routine on the KeyDown event of the combobox:
VB
Private Sub MyComboBox_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles cboID.KeyDown If e.KeyCode = Keys.Delete Then sender.SelectedIndex = -1 End IfEnd Sub
But if I have many comboboxes, I have to copy the same routine over and over to all of them...Is there a way to attach the routine to the KeyDown event of all comboboxes?
Pseudocode example:
VB
Sub AttachEventOnKeyDown For Each ctl As Control In Me.Controls If TypeOf (ctl) Is ComboBox Then ' On ctl.KeyDown execute "MyDeleteRoutine(ctl)" End If NextEnd Sub
How can this be done?
I've tried posting this to a few forums, even microsoft... Hopefully this forum is the place to be.
I'm programming an application in Visual Studio 2010, namely in VB.net. I have been developing an application which uses a derived class inherited from TreeView, with the aim of putting custom objects on the nodes. The method I have been using is to have a variable array against the node (of type object) which contains variables in custom classes to contain each of the variables associated with the node.
The two problems I had to overcome were, how to serialize a TreeView, and how to serialize an array of objects (of variable type). Good thing is I overcame both of these with some work of some other folks (and 3 days of my own work).[code]....
lets say I have:
arecord.name = "A"
arecord.value = 15 ' a number of type "long"
'
I then
call records.add(arecord,arecord.name)
' so far, so good but lets look at the next record
arecord.name = "B"
arecord.value = "this is text" as opposed to a number of type "long"
'can I then
call records.add(arecord,arecord.name)
Given an object instance, how can I recurse its members (i.e. the whole object graph) for an object of a specific type, or one that inherits from a specific type?
View 1 RepliesI am developing a VB.NET application with SQL Server 2008 and I get the above error when I try to run this ASPX file. What is the cause?
[Code]...
What's a sound approach to override the CompareTo() method in a custom class with multiple approaches to comparing the data contained in the class? I'm attempting to implement IComparable(Of T) just so I have a few of the baseline interfaces implemented. Not planning on doing any sorting yet, but this will save me down the road if I need to.
Reading MSDN states mostly that we have to return 0 if the objects are equal, -1 if obj1 is less than obj2, or 1 is obj1 is greater than obj2. But that's rather simplistic.
Consider an IPv4 address (which is what I'm implementing in my class). There's two main numbers to consider -- the IP address itself, and the CIDR. An IPv4 address by itself is assumed to have a CIDR of /32, so in that case, in a CompareTo method, I can just compare the addresses directly to determine if one is greater or less than the other. But when the CIDR's are different, then things get tricky.
Assume obj1 is 10.0.0.0/8 and obj2 is 192.168.75.0/24. I could compare these two addresses a number of ways. I could just ignore the CIDR, and still regard as obj2 as being greater than obj1. I could compare them based on their CIDR, which would be comparing the size of the network (and a /8 will trump a /24 quite easily). I could compare them on both their numerical address AND their CIDR, on the off chance obj2 was actually an address inside the network defined by obj1.
What's the kind of approach used to handle situations like this? Can I define two CompareTo methods, overloaded, such that one would evaluate one address relative to another address, and the second would evaluate the size of the overall network? How would the .NET framework be told which one to use depending on how one might want to sort an array? Or do some other function that relies on CompareTo()?
I'm having trouble assigning values to an array and am getting the error, "Value of type MemberFocal.Member cannot be converted to System.Array" - MemberFocal.Member is part of a custom class and I am attempting to create an array of these objects. Here is the code:
[Code]....
I have a form that displays data. What I would like to have is a button that when pressed will display some test extran textboxes in a dimmed/transparent type of fashion. I can get that using another form, but would like to do it without the second form.
View 1 Replies1 Partial Class _Default
2 Inherits System.Web.UI.Page
3 Public Function Ohjoy(ByVal X As Integer) As Integer
[Code].....
make objects from the ToolBox using code instead of changing existing objects invisible then visible later?
View 7 RepliesI have a program like this.
Module Module1
Public Class Mstr
Public Property Prop1 As String
Public Property Prop2 As String[code]....
But it is not working as I expect it to. You can see it from.The DtlsB properties of all three DtlsA objects are having values from last iteration.
I want to let the user input objects to a richtextbox 1 object on each line, and somehow use Random.Next to select pseudorandomly a few objects, the number 'few' inputted in a textbox.
View 9 RepliesI have a user control that inherits the FW ListView and I need to dispose of two objects when the form's disposing of it's objects. Here's what I've concluded already, am I on the right track?
[Code]...
long story short, I have created a ListView type control, using UserControls for the parent control and the ListViewItems. Most the of the control is written and works fine, right up to the point where I tried to replicate the 'Control.SelectedItems(0).Index' property and the 'SelectedIndexChanged' event.
Each child object knows its index value, and could pass this value via the SelectedIndexChanged event (assuming this is how it works in a normal ListView control -- user clicks on an item, and that item fires an event updating the selected index value in the parent object).
How does the child object raise an event in the parent object? I have a feeling this could be done with Delegates, but I'm still learning about their usage.
getting the following error Unable to cast object of type 'System.Object[]' to type 'OrderService.webdirect_WebLinesRow[]'. On the line
webdirect(web_companyID, web_locationCode, web_customerNumber, web_orderNumber, web_orderReference, web_orderDate, webLinesArray.ToArray(), o_Company, o_LocationCode, o_CustomerNumber, o_OrderNumber, o_OrderStatus, o_OrdDescrip, webRespArray)
I created the webLinesArray.ToArray() array as such
Dim webLinesArray As New ArrayList()
Am I missing an additional cast or something ?
I want to compare two objects to check if all the properites of both the object have same value or not. for this i need to use the reflection to enumarate through all the properties of an object and check the value of the property. To try the code just i have written a Employee Class having Two Properties EmployeeNo and EmployeeName. I am creating an object of the Employee class and need to write a function that can list the values of all the properties in the class.
[Code]...
I have a function that is getting passed a String and a DataRow.The String is a custom formatter. The idea is to do this
String.Format(passed_in_String, DataRow("ColumnINeed"))
The reason this is being done is at this point we have no idea what the column contains.However, if the formatter is "{0:MM/dd/yyyy}" and the DataRow("ColumnINeed") is an integer containing 42, String.Format is returning: MM/dd/yyyy In this situation I need it to throw an exception instead of returning nonsense.Is there anyway to make String.Format throw an exception if the object does not match what the format string is expecting?
