I am writing a program in Visual Basic that writes and reads to and from a Microsoft Access Database. When reading from the database, one of the functions that I am trying to perform is to determine the number of lines in a multi-line string that was written to the database and then subsequently read from the database. Here's what I have tried so far with no luck.
Dim stringLines() As String = databaseReader("multilineString").ToString.Split(CChar("Environment.NewLine"))
Dim stringLinesCount As Integer = stringLines.Length
For some reason, this always results in stringLinesCount being equal to one, regardless of how many lines the string has. In this example, I am using Environment.NewLine, but I have tried \n, \r, vbCr, vbLf, and vbCrLf as well, and they all result in a value of one. Since none of these seem to be working, what can I use instead to determine the number of lines?
Edit:
Dim splitCharacters() As Char = {CChar(vbCrLf), CChar(vbCr), CChar(vbLf), CChar(Environment.NewLine), CChar("\n"), CChar("\r")}
Dim stringLines() As String = databaseReader("multilineString").ToString.Split(splitCharacters)
Dim stringLinesCount As Integer = stringLines.Length
Since Chris Dunaway provided the answer that I view as helpful but posted it as a comment, here's what he said:
VB cannot use C# style escape sequences, so CChar("\n") and CChar("\r") is meaningless in VB. Also, calling CChar("Environment.NewLine") is wrong because you are trying to convert the actual string "Environment.NewLine" to a single character, which obviously won't work. You can just use Environment.Newline directly in the call to String.Split.
If Chris decides to post his comment as an answer, please let me know so that I may remove this.
Related
I am trying to program a way to read a text file and match all the values and their quantites. For example if the text file is like this:
Bread-10 Flour-2 Orange-2 Bread-3
I want to create a list with the total quantity of all the common words. I began my code, but I am having trouble understanding to to sum the values. I'm not asking for anyone to write the code for me but I am having trouble finding resources. I have the following code:
Dim query = From data In IO.File.ReadAllLines("C:\User\Desktop\doc.txt")
Let name As String = data.Split("-")(0)
Let quantity As Integer = CInt(data.Split("-")(1))
Let sum As Integer = 0
For i As Integer = 0 To query.Count - 1
For j As Integer = i To
Next
Thanks
Ok, lets break this down. And I not seen the LET command used for a long time (back in the GWBASIC days!).
But, that's ok.
So, first up, we going to assume your text file is like this:
Bread-10
Flour-2
Orange-2
Bread-3
As opposed to this:
Bread-10 Flour-2 Orange-2 Bread-3
Now, we could read one line, and then process the information. Or we can read all lines of text, and THEN process the data. If the file is not huge (say a few 100 lines), then performance is not much of a issue, so lets just read in the whole file in one shot (and your code also had this idea).
Your start code is good. So, lets keep it (well ok, very close).
A few things:
We don't need the LET for assignment. While older BASIC languages had this, and vb.net still supports this? We don't need it. (but you will see examples of that still floating around in vb.net - especially for what we call "class" module code, or "custom classes". But again lets just leave that for another day.
Now the next part? We could start building up a array, look for the existing value, and then add it. However, this would require a few extra arrays, and a few extra loops.
However, in .net land, we have a cool thing called a dictionary.
And that's just a fancy term of for a collection VERY much like an array, but it has some extra "fancy" features. The fancy feature is that it allows one to put into the handly list things by a "key" name, and then pull that "value" out by the key.
This saves us a good number of extra looping type of code.
And it also means we don't need a array for the results.
This key system is ALSO very fast (behind the scene it uses some cool concepts - hash coding).
So, our code to do this would look like this:
Note I could have saved a few lines here or there - but that would make this code hard to read.
Given that you look to have Fortran, or older BASIC language experience, then lets try to keep the code style somewhat similar. it is stunning that vb.net seems to consume even 40 year old GWBASIC type of syntax here.
Do note that arrays() in vb.net do have some fancy "find" options, but the dictionary structure is even nicer. It also means we can often traverse the results with out say needing a for i = 1 to end of array, and having to pull out values that way.
We can use for each.
So this would work:
Dim MyData() As String ' an array() of strings - one line per array
MyData = File.ReadAllLines("c:\test5\doc.txt") ' read each line to array()
Dim colSums As New Dictionary(Of String, Integer) ' to hold our values and sum them
Dim sKey As String
Dim sValue As Integer
For Each strLine As String In MyData
sKey = Split(strLine, "-")(0)
sValue = Split(strLine, "-")(1)
If colSums.ContainsKey(sKey) Then
colSums(sKey) = colSums(sKey) + sValue
Else
colSums.Add(sKey, sValue)
End If
Next
' display results
Dim KeyPair As KeyValuePair(Of String, Integer)
For Each KeyPair In colSums
Debug.Print(KeyPair.Key & " = " & KeyPair.Value)
Next
The above results in this output in the debug window:
Bread = 13
Flour = 2
Orange = 2
I was tempted here to write this code using just pure array() in vb.net, as that would give you a good idea of the "older" types of coding and syntax we could use here, and a approach that harks all the way back to those older PC basic systems.
While the dictionary feature is more advanced, it is worth the learning curve here, and it makes this problem a lot easier. I mean, if this was for a longer list? Then I would start to consider introduction of some kind of data base system.
However, without some data system, then the dictionary feature is a welcome approach due to that "key" value lookup ability, and not having to loop. It also a very high speed system, so the result is not much looping code, and better yet we write less code.
For my current project in need a way to use ä,ö etc. in a datatable that is written to a .csv
It is the same project as in: VB Reading data from SQL Server to Array, writing into .CSV
I know that I need UTF-8 but how do I use it ?
Unlike VB6/VBScript/VBA, VB.Net strings already use full Unicode internally. You can already put accented characters in your string variables (and string members for other objects), and you don't need to do anything special.
There are three things you do need to watch for, though.
First, you must be sure to use NVARCHAR rather than VARCHAR for your Sql Server columns, as well as your ADO.Net parameters. You may also need to be careful about what collation you have (but the default is almost certainly fine here).
Second, when you open your StreamWriter, you need to use unicode-capable correct Encoding. System.Text.UTF8Encoding is one option. You could also do System.Text.UnicodeEncoding (which is UTF16) or System.Text.UTF32Encoding and get accurate output.
Finally, just because you successfully create a unicode CSV file, this does not mean your downstream consumers will handle the file correctly. A lot of text editors and other tools like to assume csv data is ASCII. But that's really outside of your scope. All you can is give them valid data. If they don't process it, that's on them :)
So assuming the database is correct, and based on the other question, you have this code:
Sub WriteCsvFiles(destPath As String, headings As String(), dt As DataTable)
Dim separator As Char = ";"c
Dim header = String.Join(separator, headings)
For Each r As DataRow In dt.Rows
Dim destFile = Path.Combine(destPath, r(0).ToString().Trim() & ".csv")
Using sw As New StreamWriter(destFile)
sw.WriteLine(header)
sw.WriteLine(CsvLine(r.ItemArray, separator))
End Using
Next
End Sub
This is close. However, take a look at the remarks in the documentation for the StreamWriter constructor:
This constructor creates a StreamWriter with UTF-8 encoding without a Byte-Order Mark (BOM), so its GetPreamble method returns an empty byte array. The default UTF-8 encoding for this constructor throws an exception on invalid bytes. This behavior is different from the behavior provided by the encoding object in the Encoding.UTF8 property.
So we kind of already have UTF-8 data, but to really have a correct UTF-8 file, including correct byte-order handling for certain wide characters, we need to change things just a little bit. Where you have this right now:
Using sw As New StreamWriter(destFile)
should become:
Using sw As New StreamWriter(destFile, False, Encoding.UTF8)
It also seems very odd to create a separate file for every row that will all have the same structure. I know it's in your original question, but I'd really push back on that, or find out why, and the maybe re-write the method as so:
Sub WriteCsvFile(destFile As String, headings As IEnumerable(Of String), dt As DataTable)
Dim separator As Char = ";"c
Dim header As String = String.Join(separator, headings)
Using sw As New StreamWriter(destFile, False, Encoding.UTF8)
sw.WriteLine(header)
For Each r As DataRow In dt.Rows
sw.WriteLine(CsvLine(r.ItemArray, separator))
Next
End Using
End Sub
I have files coming into SFTP that are in the following format: 12345678_STLREPT. On occasion, they have two underscores instead of one. ie: 12345678__STLREPT. This throws my sorting program through a loop. So I attempted to do the top line of code below first, it threw an I/O exception. The second line I can make work if I add "__" as a delimiter, but my question is how does Name.Split work. I haven't been able to determine through my google searches if it stops at the first delimiter it finds in the string.
Basically, If it goes through the list of delimiters it would ideally match one of them, perform the split, then stop before performing the rest.
Example:
Say I have a file, named 1234__ASDF.PDF
Would the following code split it once for the first delimiter (__) then two more times for the second (_)? I feel like it would.
fileInfo.Name.Split(New Char() {"__", "_", "-"})
Is anyone aware of a better solution to this problem?
Thank you,
Code, again. Top throws error, bottom is existing code:
fileInfo = fileInfo.Name.Replace("__", "_")
Dim a() As String = fileInfo.Name.Split(New Char() {"_", "-"})
First, be aware of your data types and what you are stuffing into them. A Char holds a single character. Trying to stuff two hyphens into a Char - for shame.
Next, be aware of your tools. The Split function accepts a second parameter that controls how empty elements should be handled. It also includes overloads for accepting a string array.
Dim fileParts As String() = fileInfo.Name.Split(
New Char() {"_", "-"},
StringSplitOptions.RemoveEmptyEntries)
I am retrieving data from web. Data is seperated by each line. Data looks like this
Data1
Data2
Data3
I want to alert for each data found on the webpage. Tried this,
Dim Lines() As String
Dim stringSeparators() As String = {vbCrLf}
Dim Source As String
Dim wc As New WebClient
Source = wc.DownloadString("http://www.example.com/data.php")
Lines = Source.Split(stringSeparators, StringSplitOptions.None)
For Each s As String In Lines
MsgBox(s)
Next
But unfortunately, it alerts once all the data. My question is, how to alert for each data ?
vbCrLf, as defined in Constants, won't match a single UNIX-style newline - "Newline" (\n), LF/LINEFEED, ASCII 10 - character as transmitted from PHP.
To deal with both Windows and UNIX/Linux end-of-line sequences, use:
Dim stringSeparators() As String = {vbLf, vbCrLf}
The order the separators supplied does not matter, see the remarks in String.Split for details.
While the above solves the problem in a fairly robust manner, it may better to use the exact EOL format, especially when writing - and to make a selection prior based on established format. In this case that might be only using vbLf which would work for the given PHP output, but would incorrectly leave in CR characters for Windows text files.
When dealing with system-native text files, or Windows components such as Controls, vbNewLine should generally be preferred over vbCrLf: vbCrlLf is appropriate when the goal is to be explicit, as above, and only accept/emit a specific ASCII sequence as mandated by protocols and conventions.
When dealing with whitespace characters, I often end up running the String.Asc() method on them, to see what they really are.
http://msdn.microsoft.com/en-us/library/microsoft.visualbasic.strings.asc(v=vs.110).aspx
Then, you can ensure that you are splitting on the correct character.
In one of the ms-access table I work with we have a text field with a set size.
At the end of this field there is some extra code that varies depending on the situation.
I'm looking for a way to remove one of these code but even when the last part is truncated by the field maximum size.
Let's call the field "field" and the code I'm looking to remove "abc-longcode".
If I use the replace SQL function with the string abc-longcode the query will only work when the code is complete.
If I also want my update query (that does nothing but remove this specific code at the end of my field) to work on incomplete codes how would that translate into ms-SQL?
It would have to remove (or replace with "" to be precise) all of the following (example of course, not the real codes):
abc-longcode
abc-longcod
abc-longco
abc-longc
abc-long
abc-lon
abc-lo
abc-l
Obviously I could do that with several queries. Each one replacing one of the expected truncated codes... but it doesn't sound optimal.
Also, when the field is big enough to get all of the code, there can sometime be extra details at the end that I'll also want to keep so I cannot either just look for "abc-l" and delete everything that follows :\
This query (or queries if I can't find a better way) will be held directly into the .mdb database.
So while I can think of several ways to do this outside of a ms-sql query, it doesn't help me.
Any help?
Thanks.
You can write a custom VBA replace method that will replace any of the given cases {"abc-longcode", ... "abc-l"}. This is essentially the same tack as your "several queries" idea, except it would only be one query. My VBA is rusty, but something like:
public function ReplaceCodes(str as string) as string
dim returnString as string
returnString = str
returnString = replace(returnString,"abc-longcode","")
// ... etc...
ReplaceCodes = returnString
end function
I may have gotten the parameter order wrong on replace :)
I would use my own custom function to do this using the split function to get the first part of the string. You can then use that value in the update query.
Public Function FirstPart(thetext As String) As String
Dim ret As String
Dim arrSplitText As Variant
arrSplitText = Split(thetext, "-")
ret = arrSplitText(0)
FirstPart = ret
End Function
Can you use:
Left(FieldX,InStr(FieldX,"abc-")-1)
EDIT re Comment
If there is a space or other standard delimiter:
IIf(InStr(InStr(FieldX, "abc-"), FieldX, " ") = 0, Left(FieldX, InStr(FieldX, "abc-") - 1), Replace(FieldX, Mid(FieldX, InStr(FieldX, "abc-"), InStr(InStr(FieldX, "abc-"), FieldX, " ") - InStr(FieldX, "abc-")), ""))