I am working on a Revit Add-in and in that add-in I am trying to use a List(Of List(Of Curve)), however I'm having issue accessing the data from the sublists.
Dim ClosedCurveList As New List(Of List(Of Curve))
Dim ClosedCurve As new List (Of Curve)
For i=0 To FinalWallLines.Count-1
If FinalWallLines(i+1).GetEndPoint(0).X = FinalWallLines(i).GetEndPoint(1).X And _
FinalWallLines(i+1).GetEndPoint(0).Y = FinalWallLines(i).GetEndPoint(1).Y And _
FinalWallLines(i+1).GetEndPoint(0).Z = FinalWallLines(i).GetEndPoint(1).Z Then
ClosedCurve.Add(FinalWallLines(i))
Else
TaskDialog.Show("A",ClosedCurve.Count)
ClosedCurveList.Add(ClosedCurve)
TaskDialog.Show("B", ClosedCurveList(ClosedCurveList.Count-1).Count)
ClosedCurve.Clear()
End if
Next
TaskDialog.Show("C", ClosedCurveList.Count)
For i=0 To ClosedCurveList.Count-1
TaskDialog.Show(i,ClosedCurveList(i).Count)
next
So when I run that code, the first TaskDialog.Show("A",ClosedCurve.Count) shows me that all of ClosedCurve are made of 4 curves, which makes sense as all my curves are forming rectangles.
My second TaskDialog.Show("B", ClosedCurveList(ClosedCurveList.Count-1).Count) also return 4 as the count for each of the sublists, as expected.
My third TaskDialog.Show("C", ClosedCurveList.Count) returns 23.
So from that, we can gather than ClosedCurveList is a list of 23 lists of 4 curves.
However, during my loop For i=0 To ClosedCurveList.Count-1, my TaskDialog.Show(i,ClosedCurveList(i).Count) returns 23 0s.
Would anyone know why I am not getting 23 4s as expected when trying to access the count of each of my sublists?
Instead of ClosedCurve.Clear() you should have ClosedCurve = new List(Of Curve).
When you add it to ClosedCurveList you are not adding a copy. You are adding the reference to the object CLosedCurve. And so, when you clear ClosedCurve, it also clears the one which was added in ClosedCurveList because they are references to the same object. By re-assigning a new List(Of Curve) to ClosedCurve, you will now have separate references, like you were originally expecting.
Related
I am trying to write, in order to export on txt file, information in two listbox with the same number of rows. I have to export them with the following format: Listbox1, Listbox2. In order to do this, I've tried to use the following code:
Using writer = New StreamWriter(SaveFileDialog1.FileName)
For Each o As Object In Form3.ListBox1.Items And Form3.ListBox2.Items
writer.WriteLine(o)
Next
End Using
I'm receiving the following error:
BC30452 Operator 'And' is not defined for types 'ListBox.ObjectCollection' and 'ListBox.ObjectCollection'.
I've also tried to perform three For Each loops, the first for the LB1, the second for the commas and the third for LB2, but I'm having it exported with content on single lines. How could I solve this?
If you use Enumerable.Zip, as suggested in another answer, then you can make the code more succinct by doing away with the explicit loop:
File.WriteAllLines(SaveFileDialog1.FileName,
Form3.ListBox1.
Items.
Cast(Of Object).
Zip(Form3.ListBox2.
Items.
Cast(Of Object),
Function(x1, x2) $"{x1}, {x2}"))
If you didn't use Zip then you can use a loop this way:
Dim items1 = Form3.ListBox1.Items
Dim items2 = Form3.ListBox2.Items
Using writer = New StreamWriter(SaveFileDialog1.FileName)
For i = 0 To Math.Min(items1.Count, items2.Count)
writer.WriteLine($"{items1(i)}, {items2(i)}")
Next
End Using
The Math.Min part is just in case there are different numbers of items in each ListBox. If you know there aren't then you can do away with that and just use one Count. If there might be different counts but you want to output all items then the code would become slightly more complex to handle that.
As the error message says, the syntax you attempted is simply not valid. There's no feature in VB.NET that does that sort of thing.
However, the .NET Framework API does provide a means for something similar, which would probably work in your case. See Enumerable.Zip(). You can use it like this:
Using writer = New StreamWriter(SaveFileDialog1.FileName)
For Each o As String In Form3.ListBox1.Items.Cast(Of Object).Zip(Form3.ListBox2.Items.Cast(Of Object), Function(x1, x2) x1 & ", " & x2)
writer.WriteLine(o)
Next
End Using
Since you said that both list boxes have the same number of items we can use the number of items in the first listbox less one (indexes start at zero) in a For loop.
I used a StringBuilder so the code does not have to throw away and create a new string on each iteration.
I used an interpolated string indicate by the $ preceding the string. This means I can insert variables in braces, right along with literals.
Call .ToString on the StringBuilder to write to the text file.
Private Sub SaveListBoxes()
Dim sb As New StringBuilder
For i = 0 To ListBox1.Items.Count - 1
sb.AppendLine($"{ListBox1.Items(i)}, {ListBox2.Items(i)}")
Next
File.WriteAllText("C:\Users\xxx\Desktop\ListBoxText.txt", sb.ToString)
End Sub
Is there a simple solution to select random strings in vb.net? I have a list of about twenty paragraphs where three need to go after each other and I want it to be random. Do I have to create a variable? Or is there a command that can be run on a button click?
One (fairly easy way) to accomplish this would be to have a collection of the paragraphs you want to use, and then use PeanutButter.RandomValueGen from the Nuget package PeanutButter.RandomGenerators (it's open-source too)
RandomValueGen.GetRandomFrom takes a collection of anything and returns a random item from the collection. As a bonus, you can specify a params list of values not to pick, so you can ensure that your paragraphs aren't repeated.
Whilst the library is written in C#, it can obviously be used from any .NET project. There are a lot of other generator methods on RandomValueGen too, if you're interested.
Full disclosure: I'm the author.
If you have a normal list, this should work:
If not, write what kind of list you have.
Dim rn As New Random
Dim selct As String = lst(rn.Next(0, lst.Count - 1))
selct is the output.
Replace lst with your list name.
if you don't want to have a dependency or need to stay on 4.0 for some odd reason or reason X, you can always try this instead
Private rnd As New Random
Public Function GetRandom(input As IEnumerable(Of String), itemToGet As Integer) As List(Of String)
If input.Count < itemToGet Then
Throw New Exception("List is too small")
End If
Dim copy = input.ToList
Dim result As New List(Of String)
Dim item As Integer
While itemToGet > 0
item = rnd.Next(0, copy.Count)
result.Add(copy(item))
copy.RemoveAt(item)
itemToGet -= 1
End While
Return result
End Function
i am a noob, so please take this question with that in mind. Here is very simple piece of code:
Sub main()
{
Dim m_Dictionary as new Dictionary(Of Integer, List(Of String))
Dim workingList as new List(Of String)
Dim workingKey as Integer
Dim keyStash as List(Of Integer)
Dim workingDict as new Dictionary(Of Integer, String)
For i=0 to 9
Do
workingKey = RandomInteger()
Loop While workingList.ContainsKey(workingKey)
For n=0 to 4
workingList.Add(RandomString())
Next
keyStash.Add(workingKey)
workingDict.Add(workingKey, workingList)
Next
' now I just want to play back the generators of random data
For each Key As Integer in keyStash
For each Entry as String in workingDict(Key).Value
Line(Entry)
Next
Next
Instead of everything playing back nicely as one might expect, I am left with a fully accurate stash of keys for the dictionary. However, the values for strings inside each list instance are ALL THE SAME FOR EVERY KEY. Those values are equal to the values in the last loop of random data generation. So instead of playing back 50 uniques entries, it writes out 9 times the last loop. I looked inside - everything looks good. Get this. All lists, collections, hash-tables, all of iterated types and also custom types demonstrate this behavior. I found the solution, but it does not explain anything. Can anyone help explaining this, please!??
The variable that keeps the strings generated by RandomString is created outside the loop. Inside that loop you add continuosly new strings to the same instance and add the same list instance to every new integer key. At the end of the loop every integer key added has its value pointing to the same reference of the list. Of course they are identical....
A first fix to your code could be
Dim m_Dictionary as new Dictionary(Of Integer, List(Of String))
Dim workingKey as Integer
For i=0 to 9
' Internal to the loop. so at each loop you get a new list
' to use for the specific key generated in the current loop
Dim workingList as new List(Of String)
Do
workingKey = RandomInteger()
Loop While m_Dictionary.ContainsKey(workingKey)
For n=0 to 4
workingList.Add(RandomString())
Next
m_Dictionary.Add(workingKey, workingList)
Next
For each k in m_Dictionary
For each Entry in k.Value
' Line(Entry)
Console.WriteLine("Key=" & k.Key & " Values = " & Entry)
Next
Next
Please, remember to use Option Strict ON, the current code treats quietly strings as if they were numbers, and this is not a good practice. Option Strict ON will force you to think twice when you work with different type of data.
I'm a bit confused here. I'm copying all the controls from one form to a panel on the main form and for some reason only about half of them copy.
Private Sub switchComponent()
Dim selection As String = TreeView1.SelectedNode.Text
Panel1.Controls.Clear()
Dim query = From cont In serverDic(selection).Controls
Select cont
For Each copier As Control In query
Panel1.Controls.Add(copier)
Next
End Sub
serverDic is defined as:
Dim serverDic As New Dictionary(Of String, frmServer)
When stepping through the code, serverDic(selection).Controls has 12 elements, but only 6 of them get copied. Next time this gets called, only 3 get copied. Does Panel1.Controls.clear() somehow kill the references?
EDIT: Just to show that there are infact 12 elements in the collection:
The problem here is that you are iterating over a collection that you are changing. When you add a Control to an container it is implicitly removed from it's previous parent and hence query. This is why you see exactly half of the items get removed.
With most collections this would be more apparent because they would throw if modified during an enumeration. The primary source of query here though is ControlCollection which does allow for modifications while enumerating.
To fix this problem just add the following line before the For Each loop.
query = query.ToList()
I have this code to return a list of fund sources for our organization.
Dim FundSourceList As New List(Of FundSource)
Dim fs As New FundSource
If results.Count > 0 Then
For Each result In results
fs.FundID = result.Item("strFundID")
fs.FundDescription = result.Item("txtFundIDDescr")
fs.ShortFundDescription = result.Item("txtFundIDDescrShort")
FundSourceList.Add(fs)
Next
End If
Return FundSourceList
The problem is that when I loop through the resulting FundSourceList all it shows is the last value. For example, if I have three fund sources (state, federal, athletic), then when I use this code to loop through all I get listed is athletic, athletic, athletic.
For Each FundSource In FundSources
Debug.Print(FundSource.FundDescription)
Next
So I change the code to this. I moved the creation of the fs variable inside the loop.
Dim results = From result In dsResult.Tables(0) Select result
Dim FundSourceList As New List(Of FundSource)
If results.Count > 0 Then
For Each result In results
Dim fs As New FundSource
fs.FundID = result.Item("strFundID")
fs.FundDescription = result.Item("txtFundIDDescr")
fs.ShortFundDescription = result.Item("txtFundIDDescrShort")
FundSourceList.Add(fs)
Next
End If
Return FundSourceList
This works fine but now I'm creating a new class over and over again. It seems a little inefficient to me. Can I not create the class outside the loop and use it over and over again? Thanks.
If you have 3 fund sources, you need three FundSource objects. It's as simple as that. I don't know what's inefficient about it...
How can you add 3 fund sources to your list but just create one?
You're not actually creating a class - the class is the code definition for the methods and properties. When you use the New operation, you're creating an instance of that class, which results in an object. When you have a list of objects, like FundSourceList, you want the items in it to be individual objects. So yes, the solution you have at the bottom is correct. You mention efficiency concerns - when you instantiate the object, basically all that is happening (in this case) is some memory is being allocated to store the variables (and some references for the managed memory, but you don't need to worry about that here). This is necessary and is optimized under-the-hood, so you shouldn't need to worry about that either.
You can't instantiate the object outside of the loop to achieve the result you're after.
This is because your object would be a reference type.
By instantiating outside of the loop, you would create one reference to your object.
When iterating through your results and setting the properties, you'll be using that same reference over and over.
All you're adding to the list on each iteration is the same reference, which by the end of the loop, will refer to an object containing the last values in your result set.
By creating new objects inside the loop, you create new references - each pointing to a new FundSource. Your loop now writes into a fresh object, and get your desired results.