I currently am having some trouble trying to get my program to work with a 2D array. I had it working earlier with a 1D array but I am totally lost now that I have to make these changes.
Below is what I currently have as my 2D array and the code that I thought would work for spitting out a letter grade but does not give me anything. Would anyone be able to tell me what I'm doing wrong?
Private strGrades(,) As String = {{"900", "A"},
{"815", "B"},
{"750", "C"},
{"700", "D"},
{"0", "F"}}
Dim strGradeSearch As String
Dim intRow As Integer
strGradeSearch = txtGrade.Text
For intRow = 0 To 4
If intRow > strGrades.GetUpperBound(0) Then
strGrades(0, intRow) = strGradeSearch
intRow += 1
End If
Next intRow
If intRow <= strGrades.GetUpperBound(0) Then
lblLetter.Text = strGrades(intRow, 0)
End If
Please take all the following as positive comments :-)
OK. looking at your code, there are tbh several issues. You're trying to treat strings as numbers. While a string can contain what looks like a number, it only contains a string of characters that happen to be numbers. They make sense to use, but to a computer, they aren't. There is often stuff that VB does in the background to try and make life easier, but to be honest, it can be a pain.
When comparing something like grades, you need to compare actual numbers, not strings that contain numbers. You'll potentially get unexpected results. You need to get the computer to convert the string to a number. See below.
Your loop wont actually do anything because the If statement will never execute the code inside it because intRow will never be greater than the last element of the array. Anyhow.. Onwards.
A way to convert strings to numbers is to user the Val function, though this "old" VB. The current way is to use Integer.Parse. Have a look at this link for some basic information about it.
Lets walk through what you want to do.
Get the string in the textbox.
Convert the string to a number.
Loop through the array and for each element, get the number stored as a string and convert it to a number and then compare it to the grade number.
If the grade is greater than any of the values, make a note of the
letter linked to the grade and stop searching through the loop.
Assign the letter that was found to the label.
The following code should do this
Dim strGrades(,) As String = {{"900", "A"},
{"815", "B"},
{"750", "C"},
{"700", "D"},
{"0", "F"}}
Dim intGradeSearch As Integer
Dim strGradeLetter As String = ""
intGradeSearch = Integer.Parse(TxtGrade.Text)
For i As Integer = 0 To 4
If intGradeSearch >= Integer.Parse(strGrades(i, 0)) Then
strGradeLetter = strGrades(i, 1)
Exit For
End If
Next
LblLetter.Text = strGradeLetter
End Sub
You dont need to check intRow after the loop has finished, because in this case, at some point in the loop, a grade letter will always be found if the number in the textbox is greater than or equal to a number in the array.
If you have any questions, please don't hesitate to ask.
I have a String array which gets all the files from a directory. Dim files() as string = IO.Directory.GetFiles(xxx)
These files are being added as nodes on a TreeView. The issues I am having is, when there are 300 files in the array. I loop through and get each file and add all 300 to the Treeview. But I want to only get the first 100 files from the array and only add those. I feel like this should be pretty simple but trying to figure out how to get the first 100 strings(files) from the array is slipping my mind. Any help would be greatly appreciated.
Opt 1) Use take()
Dim files() as string = IO.Directory.GetFiles("C:\Temp").Take(6)
Opt 2) Use a for loop
Dim files() as string = IO.Directory.GetFiles("C:\Temp")
For i as Integer = 0 to 5
TreeView1.Nodes.Add(files(i))
Next
I have one 2D array that I'm wanting to populate into another. I got a bit mixed up between lists, dictionaries and simple arrays, so I'm thinking I have two different types or array. The edited code with some attempts and resulting errors:
Dim _inifile As String = "C:\Users\Steve\Scripts\Projects\IniRecEdit\Tests\insrow.ini"
Public IniLines() As String = File.ReadAllLines(_inifile)
Public _ini(IniLines.Length - 1)() As String
For I As Integer = 0 To IniLines.Length - 1
_ini(I) = IniLines(I).Split("="c)
Next
'.....code
Dim _tempini(Lines.Length - 1, SQSIZE - 1) As String
Dim tagrow As Integer
Dim tagcol As Integer
Dim taglist() As String
Dim RowSel As Integer = 1
Dim cControl As Control
For Each cControl In Me.Panel1.Controls
If cControl.Tag <> Nothing Then
taglist = Split(cControl.Tag, ","c)
If taglist(0) = "Cell" Then
tagcol = Val(taglist(1))
tagrow = Val(taglist(2))
If tagrow <= RowSel Then
If tagcol = 0 Then
_tempini(tagrow, tagcol) = _ini(tagrow)(tagcol)
Debug.WriteLine("Lower or equal then Selected row. 1st Column. From ini to row:" & tagrow)
' EDIT etc etc... more code here
Next cControl
' DIFFERENT CODE TRIED AT THIS STAGE to transfer from one array to the other:
ReDim _ini(Lines.Length - 1)
For countrow As Integer = 0 To _tempini.GetLength(0) - 1
For countcol As Integer = 0 To _tempini.GetLength(1) - 1
_ini(countrow) = _tempini(countrow)._tempini(countcol)
Next
Next
' Produces: Error 2 Number of indices is less than the number of dimensions of the indexed array.
ReDim _ini(Lines.Length - 1)
For countrow As Integer = 0 To _tempini.GetLength(0) - 1
For countcol As Integer = 0 To _tempini.GetLength(1) - 1
_ini(countrow)(countcol) = _tempini(countrow, countcol)
Next
Next
'Produces: Additional information: Object reference not set to an instance of an object.
As I say, I'm not even sure whether I'm using lists of not for "_ini" The Locals Window on Visual Studio shows the vars as:
_ini is "String()()"
_tempini is "String(,)"
I'm increasingly aware I need to go back to basics with vb and learn all of the concepts involved. However, a quick assist would let me try and complete this thing I'm knocking together with blu-tack and string :)
You are actually using arrays. The declaration of a list would look like this:
Dim myList As New List(Of String)()
A list has always one dimension and the initial size of a list is 0 (unless you pass an enumeration to the constructor). You have to add items one by one using the Add method. This makes the list grow dynamically.
I assume that your ini-file looks like this
key1 = value1
key2 = value2
key3 = value3
Also I assume that the value does not contain an equal sign, otherwise I would look for the first instance of an equal sign an split the string there "manually".
Using a two dimensional array seems not appropriate in order to store key-value-pairs. There is a handy struct KeyValuePair(Of TKey, TValue) you could use if you need a string or a list. Using an array of KeyValuePairs has the advantage that you will not have to deal with two-dimensional arrays.
However, if you want to look up values for given keys, the Dictionary(Of TKey, TValue) is more appropriate, as it is optimized for a very fast lookup.
Dim dict As New Dictionary(Of String, String)
For i As Integer = 0 To IniLines.Length - 1
Dim parts = IniLines(i).Split("="c)
dict.Add(parts(0).Trim(), parts(1).Trim())
Next
Then you can retrive a value like this
Dim value As String
If dict.TryGetValue("some key", value) Then
' Use the value
Else
' Sorry, key does not exist
End If
Or if you are sure that the key you are looking for really exists, you can simply write
value = dict("some key")
TLDR
(1) Working with Arrays...
(2) Why are you getting "Object reference
not set to an instance of an object."
(3) Multidimensional Arrays
and Arrays of Arrays
(4) Why are you getting "Number of indices is
less than the number of dimens..."
(5) What I would do if I were
you...
Working with Arrays : Declaration(1) and Instanciation(2)
(1) declaration is when you write the name of a variable and its type. You can then access the object reffered by this variable in your code.
(2) we can talk about (variable/object) instanciation when an actual object has been created and registered somewhere in the memory. You can then manipulate that object via something that points to that object : the variable.
A declaration doesn't always mean the actual object is created. (I won't dig in ValueType and ReferenceType, sorry guys, I'm just cutting corners while explaining things without the complex verbose of strict dotNet)
Arrays declaration is different from instanciation :
Dim myArray As String()
This is just a declaration. Your Array is Nothing at this time and therefore contains nothing. Calling something like myStringVariable = myArray(0) will throw an Exception (Object reference not set to an instance of an object) meaning your array declaration points to nowhere because you haven't created an object of type String() and made your Array declaration points to that object.
Dim myArray() As String
This is the same declaration as above. Which one is correct ? I don't know and it's a matter of taste. VB is known for letting you do things the way you want. If you're good, you'll be able to use the one or the other like breathing. In fact, I really don't care.
Dim myArray As String() = new String() {}
This is just an instanciation of your array. Your array is registered in memory, but is of length 0 (zero) and contains no single item (Length = 0).
Remeber the declaration above ? (myArray() As String or myArray As String()) In fact, there is a difference in the two syntax when you talk about instanciation :
you can write : Dim myArray(3) As String
but you can't write : Dim myArray As String(3)
The later throws an exception. The variable type (String) cannot have indexes delimiters.
Dim myArray(3) As String '...
... also declares an Array and instanciate it with 4 predefined items like below.
Dim myArray As String() ' this is a declaration.
Redim myArray(3) ' this is an instanciation with a defined size.
This is one another way to define the number of items in your array using the Redim keyword. You have 4 "slots" in that Array from index [0] to index [3]. Your array looks like this :
[0][""]
[1][""]
[2][""]
[3][""]
.
Dim myArray As String = New String(3) {}
This is the same as above, but in one line : you're declaring and instanciating an Array of String that contains 4 items of type String which are all empty string (they are not Nothing)
Dim myArray() As String = { "One", "Two", "Three", "Four" }
This is a one line declaration, instanciation and items-setting :
[0]["One"]
[1]["Two"]
[2]["Three"]
[3]["Four"]
Redim
Redim is used to redifine the number of items in an Array. One dimensional arrays just behaves the way they are supposed to.
Suppose you have defined your array as :
Dim myArray() As String = { "One", "Two", "Three", "Four" }
Obviously, you have four String. Then use Redim :
Redim myArray(6) ' to get 7 items ..!
This is what you get :
[0][""]
[1][""]
[2][""]
[3][""]
[4][""]
[5][""]
[6][""]
You can resize an Array, but to keep the items inside, you'll have to use a keyword : Preserve
Redim Preserve myArray(6)
myArray(4) = "Five"
'myArray(5) = "Six"
myArray(6) = "Seven"
Because I've commented out the setting of the sixth item, the array will look like this :
[0]["One"]
[1]["Two"]
[2]["Three"]
[3]["Four"]
[4]["Five"]
[5][""] ' Empty String.
[6]["Seven"]
What happens if you Redim Preserve the Array above twice while killing some items ?
Redim Preserve myArray(2)
Redim Preserve myArray(6)
' You get :
[0]["One"]
[1]["Two"]
[2]["Three"]
[3][""]
[4][""]
[5][""]
[6][""]
You've lost items 3..6 ! Don't expect to get them back.
Public _ini(IniLines.Length - 1)() As String
What this code does ? Writing Dim myArray(3)() As String ("3" could be any positive or null integer) results in the following Array structure :
[0][Nothing]
[1][Nothing]
[2][Nothing]
[3][Nothing]
Why are you getting Nothing but not a bidimensional array ? Not even empty strings ?
It's because the declaration above creates a ONE dimensional Array of Array (of the type defined, String here)
VB.net allows you to declare an Array of Array this way (I don't know yet if C# can - but I really don't care : I never, and will never use this type of syntax) This is not a bidimensional Array. To define the values, you'll have to create each instance of the contained Array per item (or line) and assign it to your Array.
In the declaration above, while you have explicitely initialized your Array, its contents [0..3] are still simple declarations that points to no instance of anything, thus, explaining the "Nothing" thing.
Then upon getting datas from your file, your _ini variable could look like this, depending on the content of your file (that's why I asked you to provide a sample of the content of your file) :
[0][ ["Key0" | "Value0"] ]
[1][ ["Key1" | ""] ]
[2][ [""] ]
[3][ ["Key3" | "Value3" | "OtherData" | "MoreData" | "EvenMoreData"] ]
...
Reading a (String) value can be done like follows :
Dim myStringVariable As String = _ini(0)(1) ' Gets "Value0"
=> Be carefull when you use Array or Arrays along with
multidimentional arrays. They are not the same !
Let's pick the code below :
ReDim _ini(Lines.Length - 1)
For countrow As Integer = 0 To _tempini.GetLength(0) - 1
For countcol As Integer = 0 To _tempini.GetLength(1) - 1
_ini(countrow)(countcol) = _tempini(countrow, countcol)
Next
Next
Your _tempini is a bidimentional array of String.
Your _ini is an one dimensions array of array of String.
Scan this line :
_ini(countrow)(countcol) = _tempini(countrow, countcol)
1) _ini(countrow) contains Nothing (whatever the value of countrow) = contains NO Array (of String) because you've just called ReDim _ini(Lines.Length - 1) right before the For loop.
2) Therefore your assignation _ini(countrow)(countcol) = ... is the same as running the following at runtime :
Nothing(countcol) = _tempini(countrow, countcol)
Nothing is not an Array, so the (countcol) indexing has no meaning : you're indexing an item value to an object expected to be an Array that doesn't even exist.
That's why you get the Exception Object reference not set to an instance of an object.
Multidimensional Arrays / Redim / Preserve
The declaration and instanciation above still apply !
Public myBiDiArray(,) As String ' Declaration ONLY : bi dimensional array
Public myBiDiArray(2,1) As String ' Declaration AND Instanciation
Public myBiDiArray(,) As String = New String(2, 1) {} ' Dec. + Inst.
Public myBiDiArray(,) As String = _
{ {"One", "Un"}, {"Two", "Deux"}, {"Three", "Trois"} }
' ^^ Declaration + Instanciation + Item Setter
Public myBiDiArray(,) As String = _
New String(,) { {"One", "Un"}, {"Two", "Deux"}, {"Three", "Trois"} }
' ^^ Declaration + Instanciation + Item Setter
Let's have a Bidimensional Array of String with rows and columns...
Dim myArray(2, 1) As String ' 3 lines, two columns
This array contains the following items :
Line 0 = [""][""]
Line 1 = [""][""]
Line 2 = [""][""]
Now you want to resize the Array and use the Redim (only) Keyword...
Redim myArray(5, 3) ' ...
...which would set the lines to 6 and columns to 4 :
' Array Size = 6, 4
Line 0 = [""][""][""][""]
Line 1 = [""][""][""][""]
Line 2 = [""][""][""][""]
Line 3 = [""][""][""][""]
Line 4 = [""][""][""][""]
Line 5 = [""][""][""][""]
That's great !
Now let's set a value in Row(0) and Column(0)
myArray(0, 0) = "Cell,0,0"
' You get :
Line 0 = ["Cell,0,0"][""][""][""]
Line 1 = [""] [""][""][""]
Line 2 = [""] [""][""][""]
Line 3 = [""] [""][""][""]
Line 4 = [""] [""][""][""]
Line 5 = [""] [""][""][""]
But what happens with the Preserve Keyword ?
Redim Preserve myArray(3, 2) ' 4 lines and 3 columns
You get an exception : 'ReDim' can only change the rightmost dimension.
But you must know that this Exception is not handled by the debugger unless you explicitly write a Try/Catch routine that encapsulates the Redim Preserve Code. Otherwise, the application just exit the method/function containing that piece of code without any warning and your Array remains untouched !
To redim a multidimensional array (not only the last dimension) while preserving its content, you must create a new array of the desired size and copy the content of the former one to this new array, then make your former array point to that new one...
_ini(countrow) = _tempini(countrow)._tempini(countcol)
I'm not aware of such syntax in VB.Net. Perhaps you got this from another language or a Reference that adds extensions to Arrays (like System.Linq) which extends (?) the members of an Array to itself for some purpose.., but I'm not aware of that.
It looks to me like a simple syntax error. That's why you get the Exception Number of indices is less than the number of dimensions of the indexed array.
To get the (string) value of a bidimensional array, just write :
myStringValue = _tempini(countrow, countcol)
The error warning is not pointing to the systax error though : the debugger stopped at the closing backet and discarded the remaining piece of text :
_ini(countrow) = _tempini(countrow ... ' <- compiler expects a comma here.
Writing this will produce the following error :
myStringValue = _tempini(countrow, countcol)._tempini(countcol)
Compiler Error : 'tempini' is not a member of 'String'.
Again, don't mess with bidimentional arrays and arrays of arrays : Writing...
_ini(countrow) = _tempini(countrow, countcol) ' ...
... has no meaning ! Even if the syntax looks correct, the above code actually tries to assign a String value to an Array(Of String) variable, which will throw an InvalidCastException.
I'll be honest : Arrays are a great bit of fun with fixed/predefined size/dimensions. From the moment I'm working with unknown number of elements/items at runtime, I leave Arrays behind.
What I would do ?
Oh! just the same Olivier Jacot-Descombes advised you to do :) No surprise, a Dictionary is very handy in your situation.
I would also enable those two :
Option Strict On
Option Explicit On
and disable this one : Option Infer Off.
Another PERSONAL advice is to avoid using the Tag property of a control. This tag is of type Object.
some Casting should be done to get a cleaner code.
Controls are usual components you'll use anywhere. One day, I've imagined I have tied an object of type 'String' to a specific control while it actually contained a Date or even Nothing. Why ? Because I confounded two different projects and lost track of the whole thing.
pass your code to a colleague or a friend, and be sure he/she'll ask you to document it about what you've done with the Tag Property... that simply means no one want to discover the obscure underlying logic of a code involving Objects. People like to deal with strongly typed variables, easy to debug and fast performing at runtime.
Also avoid the use of Val(). Val() is very handy because it can almost convert anything. However, because of this nice feature, it adds a workload on the CPU. Again, if you know you're dealing with Int32 or Double, then use Int32.Parse() or Double.Parse() but not Val(). Most misuse of Val() on the web are related to type inference and implicit casting. Debugging such kind of glitches are a real pain. Use Val only when you have no alternative.
I think you now have almost everything you need to get your code working with little changes. I have not provided the code for the changes though :
I don't understand where your samples of code lands in your application logic
I don't know what kind of datas you're manipulating
I don't even know what's the purpose of the code.
^^ So I just addressed two things :
why you're getting errors...
since you're new to VB, I just provided a custom explanation of Arrays.
Was that the (not so) quick assist you were looking for ? I don't know. That's the best I could give right now.
OK. People have been really helpful, but not really up to totally recoding at this stage. I did find a work around, however. It aint pretty and probably is really bad practice! However, got it up and running with the code I've got.
Essentially, I just did the process in reverse, constructed a line from the components in _tempini, delimited by a "=" and then just re-ran the original procedure for populating the _ini array in the first place. A total work-around, but hope will help any other amateurs like me getting stuck in these early stages.
However, I would say follow these fellas advice! Look into list, dictionaries etc before starting your code.
The fix:
ReDim _ini(((_tempini.Length) / 2) - 1)
Dim _newiniline As String
_newiniline = ""
For countrow As Integer = 0 To (((_tempini.Length) / 2) - 1)
For countcol As Integer = 0 To 1
_newiniline = _newiniline & _tempini(countrow, countcol)
If countcol = 0 Then
_newiniline = _newiniline & "="
End If
_ini(countrow) = _newiniline.Split("="c)
Next
_newiniline = Nothing
Next
I seem to have a fairly simple problem which is giving me grief. The following code throws a 'Subscript out of range' error. Therefore, I assume that the array is not being populated? Can anyone spot the glaring hole in what am I doing wrong...?
Dim p() As Variant
p = Sheet4.Range("G20:G29")
Sheet4.Select
Range("R2") = p(0)
ps G20:G29 contain strings, no blank cells
Hold it. Figured out the syntax. Forgot the Variant array was multidimensional
'First item
Range("R2") = p(1, 1)
'Second item
Range("R2") = p(2, 1)
Hey i'm having problems creating a simple button for a programme which finds the largest word in an array and puts it into a textbox. I've done most of the coding (I hope) was wondering if somebody could help me actually with the code that finds the largest text in the array as I am struggling the most with that.
Private Sub btnLongName_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLongName.Click
Dim LongName As String
Dim LengthOfLongestName As Integer
Dim UltimateName As String
For i As Integer = 0 To 5
LongName = Members(i).Name
LengthOfLongestName = Len(LongName)
If Members(i).Name.Length > LengthOfLongestName Then
End If
Next i
txtResult.Text = "The longest name is " & UltimateName & " ."
End Sub
End Class
Thanks for your time - its for college homework, struggling big time on it :(
edit: I've edited the code
Since this is homework, I won't write the code for you; instead I'll try to give you some hints that will point you in the right direction.
Declare a variable of an appropriate type to hold the <longest value so far>, initialize it with the "shortest" value for that type.
Loop through all the values in the array (perhaps with a For or For Each loop)
Pseudo-code for the inside your loop:
If the Length of <the value being checked> exceeds _
the Length of the <longest value so far> Then
Assign <the value being checked> to the <longest value so far>
End If
When the loop finishes, the <longest value so far> will be the longest value in the array.
Notes
You can use MSDN as a reference on how to use a For loop or a For Each loop (If you haven't learned For loops yet, you can also use a Do Loop)
<the value being checked> will be different on each iteration through the loop; it should correspond to each consecutive value in your array. You can verify that this is working by setting a breakpoint.
You can get the length of a string by saying myString.Length
If you've learned about Functions, consider writing a function that takes an array as a parameter, and returns the longest value in the array.
There are certainly ways you could do this with LINQ, but I don't think that is the goal of the assignment ;-]
In response to Edit 1:
Your If statement needs to be inside of some sort of loop (For, For Each, Do, etc) I think this is the key concept that you are missing.
Instead of comparing LongName.Length to LengthOfLongestName, you need to compare the length of an entry in your array to LengthOfLongestName
You're on the right track with Members(0).Name.Length, but you can't just check element 0; you have to check every element in the array.
Given your current code, you'll probably be assigning <An entry in your array>.Name to LongName
The last index in a one-dimensional array is <array>.Length - 1 or <array>.GetUpperBound(0).
The following doesn't really address anything in your assignment, but I hope it will give you some ideas on how to go through all the items in your list:
' A For loop that does a message box for each of the numbers from 0 to 5 '
For i as Integer = 0 To 5
MessageBox.Show(i)
Next i
' Code that does a message box with the names of the 2nd, 3rd and last '
' entries in Members '
' (Remember that the first item is at 0, the second item is at 1, etc...) '
MessageBox.Show(Members(1).Name)
MessageBox.Show(Members(2).Name)
MessageBox.Show(Members(Members.GetUpperBound()).Name)
In response to Edit 2:
You're getting warmer...
You should only update LongName and LengthOfLongName if the current value is the longest you've seen so far (i.e. they should be assigned inside of the If statement)
You have to go to the last index of the array, not 5. See above (the response to your first edit) on how to get that last index.
You don't really need the UltimateName variable; you can just use LongName ;-]
You might want to use <stringVariable>.Length instead of Len(<stringVariable>) to be consistent.
What you are missing is a loop that checks each member, and putting the If statement inside it and make it compare the length of the name to the longest name that you have found so far. If the name is longer, put it in the variable for the longest found, and update the length variable.
You can either initialise the variables with the name of the first member and loop from the second member and on, or you can initialise the variables with an empty string and loop all the members. Personally I prefer the latter one.