I need to select a file from a directory and move to another directory. In order to do that I need to select a file randomly.
I need to select a random file (any ext can be) but I dont know how to use return because I am new to VB.NET. So please give ideas and code.
Like this?
Sub MoveRandomFile(from$, to$)
Static r As New Random
Dim Files = New IO.DirectoryInfo([from]).GetFiles
Dim FileToMove = Files(r.Next(0, Files.Count))
IO.File.Move(FileToMove.FullName, FileToMove.FullName.Replace([from], [to]))
End Sub
Or if you just want to return a random file:
Function GetRandomFile(folder$) As IO.FileInfo
Static r As New Random
Dim Files = New IO.DirectoryInfo(folder).GetFiles
Return Files(r.Next(0, Files.Count))
End Function
The static keyword creates the variable the first time the method is called, and keeps it for the next time.
The reason we need to do that is because the random object uses a seed, like in Minecraft, and this seed is generated using information about the running process. So if you create a new random object each time it will choose the same file each time.
Related
First, I am not a programmer, I mainly just do simple scripts however there are somethings that are just easier to do in VB, I am pretty much self taught so forgive me if this sounds basic or if I can't explain it to well.
I have run into an issue trying to load a multi-column text file into a list box. There are two separate issues.
First issue is to read the text file and only grab the first column to use in the listbox, I am currently using ReadAllLines to copy the text file to a string first.
Dim RDPItems() As String = IO.File.ReadAllLines(MyDocsDir & "\RDPservers.txt")
However I am having a difficult time finding the correct code to only grab the first Column of this string to put in the listbox, if I use the split option I get an error that "Value of type '1-dimensional array of String' cannot be converted to 'String'"
The code looked like
frmRDP.lstRDP.Items.Add() = Split(RDPItems, ";", CompareMethod.Text)
This is the first hurdle, the second issue is what I want to do is if an item is selected from the List box, the value of the second column gets pulled into a variable to use.
This part I'm not even sure where to begin.
Example data of the text file
Server1 ; 10.1.1.1:3389
Server2 ; 192.168.1.1:8080
Server3 ; 172.16.0.1:9833
.....
When it's working the application will read a text file with a list of servers and their IPs and put the servers in a listbox, when you select the server from the listbox it and click a connect button it will then launch
c:\windows\system32\mstsc.exe /v:serverip
Any help would be appreciated, as I can hard code a large list of this into the VB application it would be easier to just have a text file with a list of servers and IPs to load instead.
The best practise for this would probably be to store your "columns" in a Dictionary. Declare this at class level (that is, outside any Sub or Function):
Dim Servers As New Dictionary(Of String, String)
When you load your items you read the file line-by-line, adding the items to the Dictionary and the ListBox at the same time:
Using Reader As New IO.StreamReader(IO.Path.Combine(MyDocsDir, "RDPservers.txt")) 'Open the file.
While Reader.EndOfStream = False 'Loop until the StreamReader has read the whole file.
Dim Line As String = Reader.ReadLine() 'Read a line.
Dim LineParts() As String = Line.Split(New String() {" ; "}, StringSplitOptions.None) 'Split the line into two parts.
Servers.Add(LineParts(0), LineParts(1)) 'Add them to the Dictionary. LineParts(0) is the name, LineParts(1) is the IP-address.
lstRDP.Items.Add(LineParts(0)) 'Add the name to the ListBox.
End While
End Using 'Dispose the StreamReader.
(Note that I used IO.Path.Combine() instead of simply concatenating the strings. I recommend using that instead for joining paths together)
Now, whenever you want to get the IP-address from the selected item you can just do for example:
Dim IP As String = Servers(lstRDP.SelectedItem.ToString())
Hope this helps!
EDIT:
Missed that you wanted to start a process with it... But it's like charliefox2 wrote:
Process.Start("c:\windows\system32\mstsc.exe", "/v:" & Servers(lstRDP.SelectedItem.ToString()))
Edit: #Visual Vincent's answer is way cleaner. I'll leave mine, but I recommend using his solution instead. That said, scroll down a little for how to open the server. He's got that too! Upvote his answer, and mark it as correct!
It looks like you're trying to split an array. Also, ListBox.Items.Add() works a bit differently than the way you've written your code. Let's take a look.
ListBox.Items.Add() requires that you provide it with a string inside the parameters. So you would do it like this:
frmRDP.lstRDP.Items.Add(Split(RDPItems, ";", CompareMethod.Text))
But don't do that!
When you call Split(), you must supply it with a string, not an array. In this case, RDPItems is an array, so we can't split the entire thing at once. This is the source of the error you were getting. Instead, we'll have to do it one item at a time. For this, we can use a For Each loop. See here for more info if you're not familiar with the concept.
A For Each loop will execute a block of code for each item in a collection. Using this, we get:
For Each item In RDPItems
Dim splitline() As String = Split(item, ";") 'splits the item by semicolon, and puts each portion into the array
frmRDP.lstRDP.Items.Add(splitline(0)) 'adds the first item in the array
Next
OK, so that gets us our server list put in our ListBox. But now, we want to open the server that our user has selected. To do that, we'll need an event handler (to know when the user has double clicked something), we'll have to find out which server they selected, and then we'll have to open that server.
We'll start by handling the double click by creating a sub to deal with it:
Private Sub lstRDP_MouseDoubleClick(sender As Object, e As MouseEventArgs) Handles lstRDP.MouseDoubleClick
Next, we'll get what the user has selected. Here, we're setting selection equal to the index that the user has selected (in this case, the first item is 0, the second is 1, and so on).
Dim selection As Integer = lstRDP.SelectedIndex
Lastly, we need to open the server. I'm assuming you want to do that in windows explorer, but if I'm mistaken please let me know.
Dim splitline() As String = Split(RDPItems(selection), ";")
Dim location As String = Trim(splitline(1))
We'll need to split the string again, but you'll notice this time I'm choosing the item whose location in the array is the same as the index of the list box the user has selected. Since we added our items to our listbox in the order they were added to our array, the first item in our listbox will be the first in the array, and so on. The location of the server will be the second part of the split function, or splitline(1). I've also included the Trim() function, which will remove any leading or trailing spaces.
Finally, we need to connect to our server. We'll use Process.Start() to launch the process.
Process.Start("c:\windows\system32\mstsc.exe", "/v:" & location)
For future reference, to first argument for Process.Start() is the location of the process, and the second argument is any argument the process might take (in this case, what to connect to).
Our final double click event handler looks something like this:
Private Sub lstRDP_MouseDoubleClick(sender As Object, e As MouseEventArgs) Handles lstRDP.MouseDoubleClick
Dim selection As Integer = lstRDP.SelectedIndex
Dim splitline() As String = Split(RDPItems(selection), ";")
Dim location As String = Trim(splitline(1))
Process.Start("c:\windows\system32\mstsc.exe", "/v:" & location)
End Sub
A final note: You may need to put
Dim RDPItems() As String = IO.File.ReadAllLines(MyDocsDir & "\RDPservers.txt")
outside of a sub, and instead just inside your class. This will ensure that both the click handler and your other sub where you populate the list box can both read from it.
Following code should sum two numbers from file "input.txt" and write the sum to "output.txt". Compilation is succesfull, but "output.txt" is still empty after running program. What am I doing wrong?
Imports System.IO
Public Class test
Public Shared Sub Main()
Dim scan as StreamReader = new StreamReader("input.txt")
Dim writer as StreamWriter = new StreamWriter("output.txt", True)
Dim input as String
input = scan.ReadLine()
Dim ab() as String = Split(input)
Dim res as Integer = Val(ab(0))+Val(ab(1))
writer.writeLine(res)
writer.close()
End sub
End class
Your code works properly for me, so as long as your input file is formatted properly (i.e. a single line with two numbers separated by spaces, like "1 2") and you have the necessary OS permissions to read and write to those files, then it should work for you too. However, it's worth mentioning that there are several issues with your code that would be good to correct, since the fly in the face of typical best-practices.
First, you should, as much as possible, turn Option Strict On. I know that you have it Off because your code won't compile with it On. The following line is technically misleading, and therefore fails with Option Strict On:
Dim res As Integer = Val(ab(0)) + Val(ab(1))
The reason if fails is because the Val function returns a Double, not an integer, so, technically, depending on the contents of the file, the result could be fractional or could be too large to fit in an Integer. With Option Strict Off, the compiler is essentially automatically fixing your code for you, like this:
Dim res As Integer = CInt(Val(ab(0)) + Val(ab(1)))
In order to set the res variable equal to the result of the calculation, the more capable Double value must be converted down to an Integer. When you are forced to put the CInt in the code yourself, you are fully aware that the conversion is taking place and what the consequences of it might be. When you have Option Strict Off and it inserts the conversion behind-the-scenes, then you may very well miss a potential bug.
Secondly, the Val function is old-school VB6 syntax. While it technically works fine, it's provided mainly for backwards compatibility. The new .NET equivalent would be to use Integer.Parse, Integer.TryParse or Convert.ToInt32.
Thirdly, you never close the scan stream reader. You could just add scan.Close() to the end of your method, but is better, when possible, to create Using blocks for any disposable object, like this:
Using scan As StreamReader = New StreamReader("test.txt")
Using writer As StreamWriter = New StreamWriter("output.txt", True)
Dim input As String
input = scan.ReadLine()
Dim ab() As String = Split(input)
Dim res As Integer = Integer.Parse(ab(0)) + Integer.Parse(ab(1))
writer.WriteLine(res)
End Using
End Using
Lastly, as Hans pointed out, it's not good to rely on the current directory. It's always best to specify full paths for your files. There are different methods in the framework for getting various folder paths, such as the user's desktop folder, or the download folder, or the temp folder, or the application folder, or the current application's folder, or the folder of the current running assembly. You can use any such method to get your desired folder path, and then use Path.Combine to add the file name to get the full file path. For instance:
Dim desktopFolderPath As String = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory)
Dim inputFilePath As String = Path.Combine(desktopFolderPath, "input.txt")
Dim outputFilePath As String = Path.Combine(desktopFolderPath, "output.txt")
I currently have a text file that has fixed fields. There are x number of header lines and x number of detail lines. There is one piece of information I need from the detail line so I can create a record for my program. If there is a way I can loop from the end of the file to the beginning of the file I will be able to accomplish my task.
I have the code below that does the beginning of file to the end...
Using rdr As New StreamReader(_mtLocation)
Do Until rdr.EndOfStream
'// Do code here
Loop
End Using
Is there a way to go from the end of file to the beginning?
If there is any other information you need, please let me know and I will update the question with additional information. Any help is appreciated.
You can read the file into an array of String using the File.ReadAllLines method. Then you would iterate backwards through that array, which would give you each line from bottom to top. For each line, you would iterate backwards through the line.
You can read at different position of the stream by changing the Position property. The problem happens depending on the encoding of the file.
A had a simple file (not unicode) with the number 1 through 9 written into it.
Using s = System.IO.File.OpenRead("test.txt")
For i As Integer = 8 To 0 Step -1
s.Position = i
Console.WriteLine(Chr(s.ReadByte()))
Next
End Using
There's a nice example here but in C#.
stackoverflow.com/a/452945/130611
This is another solution:
Dim TxtLines As New List(Of String)
Using rdr As New StreamReader(_mtLocation)
Do Until rdr.EndOfStream
TxtLines.Add(Reader.ReadLine.ToString())
Loop
End Using
Dim x As Integer
For x = TxtLines.Count To 0 Step -1
'Do your code here...
Next
To get the text of the current line just do this inside the For loop:
TxtLines(x).ToString()
I'm just starting out on one of my first programming projects in visual studio 2010.
I have an XML file that I have added into the program as an item. It has the following structure:
<lexeme><grapheme>Aalesund</grapheme> <phoneme>'A:lI2s,Vnd</phoneme></lexeme>
There are 400,000 entries like that and what I would like to do is on a button press have a random lexeme selected from the xml file and then two labels populated with the corresponding grapheme and phoneme.
Could anyone point me in the right direction to begin with please? The tutorials I have found are for loading specific amounts of data, not just one random line and reference an external xml file location, not one that is internal to the project.
Thanks in advance.
Edit: I should say that I mean pseudo-random number. I was hoping to find a rand() function, but can't seem to?
There isn't a direct way of getting a random line from an XML. And relying on line number is dangerous because if the format of the XML were to be changed from:
<lexeme><grapheme>Aalesund</grapheme> <phoneme>'A:lI2s,Vnd</phoneme></lexeme>
to:
<lexeme>
<grapheme>Aalesund</grapheme>
<phoneme>'A:lI2s,Vnd</phoneme>
</lexeme>
Your randomly generated line number might not line up with a <lexeme> element anymore.
I think the best way to do it is to get all of the <lexeme> elements in a list and randomly generate a number that is within the range of the list:
(forgive me, but the code sample is in c#, I don't trust my VB.Net enough to write my code in VB)
var lexemeList = xDocument.Descendants("lexeme").ToList();
var random = new Random();
var randomLexeme = lexemeList[random.Next(0, lexemeList.Count-1)];
randomLexme will then have a pseudo-random <lexeme> element and you can parse it as you need to get the appropriate <grapheme> and <phoneme> elements.
If you do this though, keep in mind that the .net Random class is pseudo-random and uses the current timestamp as a seed. If you are going to be accessing objects regularly, it would be advisable to make the var random = new Random() variable as class-level field and create it once and just used the Next() method to get the next number, rather than creating a new Random() object whenever you need a random number.
Here's a more self contained function in VB.Net:
Dim rand = New Random()
Dim myXml = New XDocument()
Function GetRandomLexeme() as XElement
Dim lexemeList = myXml.Descendants("lexeme").ToList()
Dim randomLexeme = lexemeList(rand .Next(0, lexemeList.Count - 1))
GetRandomLexeme = randomLexeme
End Function
I need your help, guys! :|
I've got myself a CSV file with the following contents:
1,The Compact,1.8GHz,1024MB,160GB,440
2,The Medium,2.4GHz,1024MB,180GB,500
3,The Workhorse,2.4GHz,2048MB,220GB,650
It's a list of computer systems, basically, that the user can purchase.
I need to read this file, line-by-line, into an array. Let's call this array csvline().
The first line of the text file would stored in csvline(0). Line two would be stored in csvline(1). And so on. (I've started with zero because that's where VB starts its arrays). A drop-down list would then enable the user to select 1, 2 or 3 (or however many lines/systems are stored in the file). Upon selecting a number - say, 1 - csvline(0) would be displayed inside a textbox (textbox1, let's say). If 2 was selected, csvline(1) would be displayed, and so on.
It's not the formatting I need help with, though; that's the easy part. I just need someone to help teach me how to read a CSV file line-by-line, putting each line into a string array - csvlines(count) - then increment count by one so that the next line is read into another slot.
So far, I've been able to paste the numbers of each system into an combobox:
Using csvfileparser As New Microsoft.VisualBasic.FileIO.TextFieldParser _
("F:\folder\programname\programname\bin\Debug\systems.csv")
Dim csvalue As String()
csvfileparser.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited
csvfileparser.Delimiters = New String() {","}
While Not csvfileparser.EndOfData
csvalue = csvfileparser.ReadFields()
combobox1.Items.Add(String.Format("{1}{0}", _
Environment.NewLine, _
csvalue(0)))
End While
End Using
But this only selects individual values. I need to figure out how selecting one of these numbers in the combobox can trigger textbox1 to be appended with just that line (I can handle the formatting, using the string.format stuff). If I try to do this using csvalue = csvtranslator.ReadLine , I get the following error message:
"Error 1 Value of type 'String' cannot be converted to '1-dimensional array of String'."
If I then put it as an array, ie: csvalue() = csvtranslator.ReadLine , I then get a different error message:
"Error 1 Number of indices is less than the number of dimensions of the indexed array."
What's the knack, guys? I've spent hours trying to figure this out.
Please go easy on me - and keep any responses ultra-simple for my newbie brain - I'm very new to all this programming malarkey and just starting out! :)
Structure systemstructure
Dim number As Byte
Dim name As String
Dim procspeed As String
Dim ram As String
Dim harddrive As String
Dim price As Integer
End Structure
Private Sub csvmanagement()
Dim systemspecs As New systemstructure
Using csvparser As New FileIO.TextFieldParser _
("F:\folder\programname\programname\bin\Debug\systems.csv")
Dim csvalue As String()
csvparser.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited
csvparser.Delimiters = New String() {","}
csvalue = csvparser.ReadFields()
systemspecs.number = csvalue(0)
systemspecs.name = csvalue(1)
systemspecs.procspeed = csvalue(2)
systemspecs.ram = csvalue(3)
systemspecs.harddrive = csvalue(4)
systemspecs.optical = csvalue(5)
systemspecs.graphics = csvalue(6)
systemspecs.audio = csvalue(7)
systemspecs.monitor = csvalue(8)
systemspecs.software = csvalue(9)
systemspecs.price = csvalue(10)
While Not csvparser.EndOfData
csvalue = csvparser.ReadFields()
systemlist.Items.Add(systemspecs)
End While
End Using
End Sub
Edit:
Thanks for your help guys, I've managed to solve the problem now.
It was merely a matter calling loops at the right point in time.
I would recommend using FileHelpers to do the reading.
The binding shouldn't be an issue after that.
Here is the Quickstart for Delimited Records:
Dim engine As New FileHelperEngine(GetType( Customer))
// To Read Use:
Dim res As Customer() = DirectCast(engine.ReadFile("FileIn.txt"), Customer())
// To Write Use:
engine.WriteFile("FileOut.txt", res)
When you get the file read, put it into a normal class and just bind to the class or use the list of items you have to do custom stuff with the combobox. Basically, get it out of the file and into a real class asap, then things will be easier.
At least take a look at the library. After using it, we use a lot more simple flat files since it is so easy, and we haven't written a file access routine since (for that kinda stuff).
http://msdn.microsoft.com/en-us/library/microsoft.visualbasic.fileio.textfieldparser.aspx
I think your main problem is understanding how arrays work (hence the error message).
You can use split and join functions to convert strings into and out of arrays
dim s() as string = split("1,2,3",",") gives and array of strings with 3 elements
dim ss as string = join(s,",") gives you the string back
Firstly, it's actually really good that you are using the TextFieldParser for reading CSV files - most don't but you won't have to worry about extra commas and quoted text etc...
The Readline method only gives you the raw string, hence the "Error 1 Value of type 'String' cannot be converted to '1-dimensional array of String'."
What you may find easier with combo boxes etc is to use an object (e.g. 'systemspecs') rather than strings. Assign the CSV data to the objects and override the "ToString" method of the 'systemspecs' class to display in the combo box how you want with formatting etc. That way when you handle the SelectedIndexChanged event (or similar) you get the "SelectedItem" from the combo box (which can be Nothing so check) and cast it as the 'systemspecs' to use it. The advantage is that you are not restricted to display the exact data in the combo etc.
' in "systemspecs"...
Public Overrides Function ToString() As String
Return Name ' or whatever...
End Function ' ToString
e.g.
dim item as new systemspecs
item.ID = csvalue(1)
item.Name = csvalue(2)
' etc...
combobox1.Items.Add(item)
Let me know if that makes sense!
PK :-)