Im learning about UDC in vb.net and trying to get a very simple program to display the value of a UDC in a textbox my code follows below:
Structure carDriverInfo
Dim carMake As String
Dim driverName As String
End Structure
Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim car As carDriverInfo
Dim driver As carDriverInfo
car.carMake = "Ford Fiesta"
driver.driverName = "J Hudgsons"
TextBox1.Text = car
TextBox2.Text = driver
End Sub
The problem is the compiler gives me the error that CarDriverInfo cannot get converted to string...
What am I doing wrong here?
Compiler doesn't know what variable to show. You can choose one value that will represent string output of your structure by adding following to your structure
Public Overrides Function ToString() As String
Return carName
End Function
But if you want to get different values from your structure you need to define your variables as properties and use those properties as you see fit like
car.carName
Related
I keep getting this error, I tried all I could but it still says "Value type of String() cannot be converted to string."
Here is the code:
Private Sub Label1_Click(sender As Object, e As EventArgs) Handles Label1.Click
End Sub
Sub New()
InitializeComponent()
RAN = New Random
WB = New WebClient
End Sub
Private Const IDNum As String = "https://example.com/Data.php"
Private WB As WebClient
Private RAN As Random
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Account As String() = WB.DownloadString(IDNum).Split(Environment.NewLine)
AccSplit(Account(RAN.Next(1, Account.Length)))
End Sub
Private Sub AccSplit(ByVal Account As String)
TextBox2.Text = Account.Split()
End Sub
When you call Split here:
TextBox2.Text = Account.Split()
You are getting a String array back. Calling Split with no arguments will split the String on whitespace characters. For instance, this:
Dim arr = "Hello World".Split()
is equivalent to this:
Dim arr = {"Hello", "World"}
The Text property of a TextBox is type String, so you can't assign a String array to it. That doesn't make sense. If you want to fry an egg, do you put am egg carton in the pan? The correct course of action depends on what you're actually trying to achieve. If you just want that String displayed in the TextBox then do this:
TextBox2.Text = Account
You could also do this:
TextBox2.Lines = Account.Split()
to display the array with the elements on separate lines in the TexTbox, which assumes that you have set its Multiline property to True.
TextBox2.Text is a string. The string.Split() function returns an array of strings (shown by Visual Studio as a string()). Those types don't match up. You can't just assign an array to a string. I might ask if you wanted this:
TextBox2.Text = String.Join(",", Account.Split())
That will at least compile. But it makes no sense... why split a string, just to join it back again?
i have a structure in a module that i instanciate a table of its type
Public Structure Client
Public _nom As String
Public _prenom As String
Public _age As Integer
End Structure
Module Module1
Public TableauClient(0) As Client
End Module
that i need to populate nd resize every time i hit a certain button
Dim Dimension As Integer = 0
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
TableauClient(Dimension)._nom = TextBox1.Text.ToString()
TableauClient(Dimension)._prenom = TextBox2.Text.ToString()
TableauClient(Dimension)._age = Val(TextBox3.Text)
Dimension += 1
ReDim TableauClient(Dimension)
End Sub
the problem is i need to fill a listbox with all the elements in the table when i hit another button but i don't even know where to start to do this, tried datasource or add item by item by using concatenations between the three fields but still couldn't get it right
you can still use the structure but, I think it will be easier to work with class. Instead of Array make a list
dim TableauClient as new List(of Client)
create toString inside your class / structure
Public Overrides Function ToString() As String
return _nom
End Function
and just add those into your listbox
listbox.items.add(TableauClient (0))
I am trying to find if mylines() contains a value or not. I can get the value by mylines.Contains method:
Dim mylines() As String = IO.File.ReadAllLines(mypath)
If mylines.Contains("food") Then
MsgBox("Value Exist")
End If
But the problem is that I want to check if mylines() contains a line which starts with my value. I can get this value from a single line by mylines(0).StartsWith method. But how do I find a string from all the lines which is starting from some value, e.g. "mysearch" and then get that line number?
I am using a for loop to do so, but it is slow.
For Each line In mylines
If line.StartsWith("food") Then MsgBox(line)
Next
Constrained to code for .NET 2.0, please.
Here's one way with Framework 2.0 code, simply set SearchString with the the string you want to search for:
Imports System.IO
Public Class Form1
Dim SearchString As String = ""
Dim Test() As String = File.ReadAllLines("Test.txt")
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
SearchString = "Food"
End Sub
Private Function StartsWith(s As String) As Boolean
Return s.StartsWith(SearchString)
End Function
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim SubTest() As String = Array.FindAll(Test, AddressOf StartsWith)
ListBox1.Items.AddRange(SubTest)
End Sub
End Class
When I test this with a file with 87,000 lines, it takes about .5 sec, to fill the listbox.
I'm not a VB guy, but I think you could use Linq:
Dim mylines() As String = IO.File.ReadAllLines(mypath)
??? = mylines.Where(Function(s) s.StartWith("food")) //not sure of the return type
Check out: How do I append a 'where' clause using VB.NET and LINQ?
I have a class as seen below:
Public Class parameters
Public Property test As String
Public Property test_type As String
Public Property user_test_name As String
Public Property meas As String
Public Property spec As String
...etc
End Class
I make a list of objects that I import from a csv somewhere. The user_test_name's from the list gets sent to a list box:
For Each parameters In param
' MsgBox(parameters.user_test_name)
ListBox1.Items.Add(parameters.user_test_name)
Next
now when the user selects something from the list i want the rest of the properties of that particular user_test_name object to populate in certain text/combo boxes in the application. Here is how I grab what is selected.
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
Dim selected_name As String = ListBox1.SelectedItem()
' MsgBox(selected_name)
find_object_by_user_test_name(selected_name)
End Sub
Now i'm having difficulty finding the object with the selected_name from the list and using its properties to fill the text.combo boxes. I tried the following to no success:
Public Sub find_object_by_user_test_name(ByVal description)
MsgBox(description)
Dim matches = From parameters In param
Where parameters.user_test_name = description
Select parameters
' MsgBox(matches)
' MsgBox(matches.user_test_name)
TextBox1.Text = matches.test
TextBox2.Text = matches.test_name
etc,,, on and on
' populate_area(matches)
End Sub
Instead of adding the name (a string) to the ListBox, add your actual INSTANCE to it.
First, override ToString() in your class so that it displays properly in your ListBox:
Public Class parameters
Public Property test As String
Public Property test_type As String
Public Property user_test_name As String
Public Property meas As String
Public Property spec As String
Public Overrides Function ToString() As String
Return user_test_name
End Function
End Class
Next, add each instance to the ListBox:
For Each parameters In param
ListBox1.Items.Add(parameters)
Next
Now, the SelectedIndexChanged() event, you can cast the SelectedItem() item back to parameters and you already have everything at your disposal:
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
If ListBox1.SelectedIndex <> -1 Then
Dim P As parameters = DirectCast(ListBox1.SelectedItem, parameters)
' ... do something with "P" ...
Debug.Print(P.user_test_name & " --> " & P.test)
End If
End Sub
If the user_test_names are unique, it may be easier to use a dictionary and retrieve the objects that way.
Dim params As New Dictionary(Of String, parameters)
params.add(MyParameterObject.user_test_name, MyParameterObject)
Then
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
Dim selected_name As String = ListBox1.SelectedItem()
Dim selected_param as parameters = params(selected_name)
End Sub
Something like this should do it:
Public Sub find_object_by_user_test_name(ByVal description As String)
' assuming param is your list of parameter objects
For Each p In param
If p.user_test_name = description Then
TextBox1.Text = p.test
TestBox2.Text = p.test_name
...
Exit For
End If
Next
End Sub
A few notes about your code. First, you can't allow two objects to have the same user_test_name. Second, you can't use parameters as a variable name if you already have a class called parameters in your current namespace (which you do).
There is a simpler solution than any of these--just do the following:
Dim i as Integer = ListBox1.SelectedIndex
Then you can use i as an index to your original list of objects.
In the code below b textbox will contain the string "a.text" what I want b textbox to be the evaluation of the content of the string "a.text" which is the word Test. Please don't suggest:
b.text = a.text
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim t As String
a.Text = "Test"
t = "a.text"
b.Text = t
End Sub
End Class
Check out Controls collection of your form. You can find an item based on its name.
Also check out this answer
VB .NET Access a class property by string value
So, you could take your string, split it by the ".", find the control using the Controls Collection, and then get the property using the second half of your string using Reflection.
Of course, if you are just looking for the Text of the textbox, you just need to use the collection and forget the reflection. Like this..
For i As Integer = 1 To 25
.fields("Field" & i).value = Me.Controls("QAR" & i).Text
Next
You can do what you asked for using Reflection ... I'm not an enormous fan of it for something like this, but here's how it would look in your code:
Imports System.Reflection
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
a.Text = "Hello"
Dim t As String = "a.Text"
b.Text = DirectCast(SetValue(t), String)
End Sub
Public Function SetValue(ByVal name As String) As Object
Dim ctrl As Control = Me.Controls(name.Split("."c)(0))
Return ctrl.GetType().GetProperty(name.Split("."c)(1)).GetValue(ctrl, Nothing)
End Function
End Class
This would set textbox a's value to "Hello" and then copy that to textbox b using the reflection method.
Hope this helps!