I'm learning to read text files and Streamreader is the only class I know until now for that purpose.
Until now I've seen this class lets me read the entire file(.ReadToEnd), line by line(.ReadLine) or character by character(.Read).
However I can't figure how to read substrings delimited by , and solve this:
( Following 4 lines are the content of textfile.txt)
COLUMN1,MAIL1,COLUMN3,COLUMN4,COLUMN5,MAIL2
".","user#DOMAIN.EDU.PE","1","2013-05-08 00:00:00","0","user#DOMAIN.EDU.PE"
".","id#DOMAIN1.COM.PE","1","2013-05-08 00:00:00","0","HADSA7#DOMAIN1.COM.PE"
".","myid#DOMAIN2.COM.PE","1","2013-05-08 00:00:00","0","4671#DOMAIN2.COM.PE"
If the first email address is equal to the second, do:
Numberofmatched=Numberofmatched+1
If not
Numberofunmatched=Numberofunmatched+1
Take in consideration domain name can change and email addresses have variable lenght.
Any help?
Here's another method to read a text-file. You can use the System.IO.File class, for example File.ReadLines/File.ReadAllLines or File.ReadAllText.
Use String.Split to get a String(), one string for each column. Since the delimiter seems to be ,instead of " use String.Split(","c).
You can use following LINQ query which can increase readability:
Dim allLines = File.ReadAllLines("Path")
Dim data = From line In allLines.Skip(1) ' skip the header-line
Where Not String.IsNullOrWhiteSpace(line)
Let fields = line.Split(","c)
Where fields.Length = 6
Select fields
Dim Numberofmatched As Int32 = data.Count(Function(fields) fields(1) = fields(5))
Dim Numberofunmatched As Int32 = data.Count(Function(fields) fields(1) <> fields(5))
Note that you should use an available CSV-parser instead of reinventing the wheel since they support quoting characters and a lot of other things. One recommendable in the Visual-Basic namespace is the TextFieldParser class.
Related
Using VB.NET (VS2013) I'd like to read a delimited file and remove a field if all records have the same blank field (could be multiple fields per record). The delimited file can have "x" number of columns and "y" number of rows and once the blank fields are removed, I need to write it back out as a new delimited file.
The input file will have a header that has to be maintained and the order of the records has to be maintained. I'm familiar with using TextParser to read the file and familiar with writing the file -- what I need help with is reading for a blank field and removing it if it exists across the entire file.
I was thinking I would have to use a datagrid but never used them so looking for some insight to point me in the direction.
Thanks!
I assume each line is delimited with a newline... open as a text file, read a line at a time and use the Split method to break up the line into an array of strings. The split method will take an argument that defines the delimiter you are using. Open the destination file and write the array of strings using a loop.
UPDATE
After thinking about it, you may have records that have a couple of blank columns and the rest have data. I'm not sure if you'd want to remove those columns, because you would lose the structure of the row if you did.
So instead of using StringSplitOptions.RemoveEmptyEntries, you can just do the Split() and then perform some Linq to find out if the Split() produced an array of empty strings.
Something like (with the same results)...
Imports System
Imports System.Linq
Public Module Module1
Public Sub Main()
Dim data As String = "|||||"
Dim pieces As String() = data.Split("|"c)
If pieces.Where(Function(p) String.IsNullOrEmpty(p) = False).Count = 0 Then
Console.WriteLine("All elements are empty")
Else
' Do something
End If
End Sub
End Module
Demo
OLD ANSWER
The String.Split() has an overload that excepts StringSplitOptions. Use StringSplitOptions.RemoveEmptyEntries with your String.Split() and if all records are blank then you'll end up with an array with a length of 0 that you can ignore.
Imports System
Public Module Module1
Public Sub Main()
Dim data As String = "|||||"
Dim pieces As String() = data.Split(new Char() {"|"}, StringSplitOptions.RemoveEmptyEntries)
If pieces.length = 0 Then
Console.WriteLine("All elements are empty")
Else
' Do something
End If
End Sub
End Module
Results:
All elements are empty
Demo
I've been asked at work to create a project to open a CSV and then use a set of conditions to change and save the data using Visual Basic.net (2010)
Although I am comfortable creating files in vb and opening them again into vb, I don't know how to declare the fields so I can query them. For example:
if field1 = "Yes" and field2 = "Blue" then textbox1.text = "abcd"
Then at a later stage I want to export a file which I'm happy doing where it writes lines to create a new CSV which could be Field1, textbox1.text, Field3 and so on
Also, would I have to declare line1.field1 and line2.field1 or could I declare line2.field1 as field25 for example or whatever the next sequential number may be?
Thanks
How are you going to read from the file?
If you do File.ReadAllLines
what does it return? A string array.
Does a string array have properties like line1? No, but they do have indexers.
How do you access an element in a string array? With a indexer,
e.g. array(0).
Does an string have properties like field1? Nope.
Can you use String.Split to split on the commas and separate the fields? Yes.
Could you write a class that has specific properties defined for each field that has a constructor that'd take a string that represents a row and put the value into the correct fields? Yes.
Could the same class know how to convert itself into a single CSV style line? Yup.
Are there other library that could help you do this? Probably.
All that being said, you can probably get away with doing something simple like this (warning: naive code sample):
Dim fileName = "C:\testFile.csv"
Dim lines = File.ReadAllLines(fileName)
Dim output As New List(Of String)
For Each line In lines
Dim fields = line.Split(","c)
fields(0) = "000" 'Blank out number
If fields(3) = "Y" Then 'Change Y to True
fields(3) = "True"
End If
output.Add(String.Join(","c, fields))
Next
File.WriteAllLines(fileName, output)
I gave it input that looked like this:
123,abc,Y,Y,N
456,def,Y,N,Y
789,ghi,N,Y,Y
012,jkl,N,N,N
and it changed the file to this:
000,abc,Y,True,N
000,def,Y,N,Y
000,ghi,N,True,Y
000,jkl,N,N,N
Utilities for working with CSV will do a better job than this. There are various ways this won't work (doesn't handle any escape sequences, etc.) but this could be sufficient if you're just wanting to do something quick and dirty and don't need to worry about some things. At the very least hopefully it'll give you a better understanding of how you'd go about solving a problem like this.
I'd recommend writing the output to a different file to test.
I'm trying like crazy to figure out how to do this. I need to look at a textfile that I've designed (for a quiz program)- line by line (the line having two parts separated by a comma) for the question (First part) and the boolean answer (second part). Ie. A line from the text file will look like:
You have 10 fingers,true
you have 10 toes,true
you have 2 thumbs,true
I just need to be able to convert this to an array whereby I can access the elements on command, so for instance (0,0) would display the first question in a textbox, and I would reference the users answer (in the form of true or false) against (0,1) where I would use a counter to count the number of correct answers. After the user answers the first question I could loop to the second question to be displayed in the array and so forth. Although there may be more advanced ways of doing this I will need to use a stream reader in this context.
I see I can read ONE line into an array with :
dim line() as string = io.file.readalllines("C:\data.txt")
dim value(2) as integer
value = line.split(","c)
but I need to access each line, with their answers, one at a time. If I could get the textfile into an two dimensional array I could simply access each element on command. Help :)
Any help would be GREATLY appreciated!
I suggest to use a proper class to handle your data. For example you could write a class named QA that stores the Question text and the boolean value of the answer
Public Class QA
Public Question as String
Public Answer as Boolean
End Class
You could read your file with File.ReadLines or use the StreamReader class.
Sub Main
' A list of QA objects loaded from file
Dim qaList as New List(Of QA)()
Using sw = new StreamReader("C:\data.txt")
Dim line as String
Do
line = sw.ReadLine()
If line Is Nothing Then Exit Do
Dim parts() = line.Split(","c)
' Initialize a new QA object and add it to the list
qaList.Add(new QA() _
With
{
.Question = parts(0),
.Answer = Convert.ToBoolean(parts(1))
})
Loop
End Using
Now you could use the List(Of QA) as an array referencing the elements using an indexer
Console.WriteLine(qaList(0).Question)
Console.WriteLine(qaList(0).Answer)
End Sub
To start here is an example of a line I am trying to manipulate:
trait slot QName(PrivateNamespace("*", "com.company.assembleegameclient.ui:StatusBar"), "_-0IA") type QName(PackageNamespace(""), "Boolean") value False() end
I wrote a code that will go through and read through each line and stop at the appropriate line. What I am trying to achieve now is to read through the characters and save just the
_-0IA
to a new string. I tried using Trim(), Replace(), and indexof so far but I am having a ton of difficulties because of the quotation marks. Has anyone deal with this issue before?
Assuming your source string will always follow a strict format with only some data changes, something like this might work:
'Split the string by "," and extract the 3rd element. Trim the space and _
quotation mark from the front and extract the first 5 characters.
Dim targetstr As String = sourcestr.Split(","c)(2).TrimStart(" """.ToCharArray).Substring(0, 5)
If the length of the target string is variable it can be done like this:
Dim temp As String = teststr.Split(","c)(2).TrimStart(" """.ToCharArray)
'Use the index of the next quotation mark instead of a fixed length
Dim targetstr As String = temp.Substring(0, temp.IndexOf(""""c))
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 :-)