I have a directory of Xml files. How do I grab only the files that have been created in the last 30 days and sort them in ascending order? I am not bound to using Directory.GetFiles if there is a more efficient solution.
I then create and bind a list of files to a gridView in which I need both the File Name and Path. I display the File Name and use the Path value in the RowDataBound event to build a HyperLink to the file.
Thanks! \m/ \m/
Dim filePaths() As String = Directory.GetFiles("C:\XmlFiles\")
Dim files As List(Of ListItem) = New List(Of ListItem)
For Each filePath As String In filePaths
files.Add(New ListItem(Path.GetFileName(filePath), filePath))
Next
gv.DataSource = files
gv.DataBind()
We can do a little better. Just getting the names and then sorting by time afterwards requires separate trips out the hard drive for both attributes, which is slow. By switching to DirectoryInfo, we can reduce this to one trip to disk per file:
Dim filesByDate = DirectoryInfo.EnumerateFiles("C:\XmlFiles\").
Where(Function(f) f.CreationTime > DateTime.Today.AddDays(-30)).
OrderBy(Function(f) f.CreationTime).
Select(Function(f) f.Name)
gv.DataSource = filesByDate
gv.DataBind()
Not that the difference is likely to drive your program's performance, but it's always nice to reduce disk I/O :)
This is also a case where it might be better to use GetX instead of EnumerateX. Generally, you want to prefer anything that will "enumerate" vs "get", because of the reduced memory use and the ability to start processing as soon as the first item is available, instead of waiting until the last item is available. In this case, though, there's a chance that you can trade memory use for disk I/O. I'm not familiar with the internal implementation of the methods, but it may be possible for GetFileSystemInfos() to get the information for all of the files in one or a few trips to disk, and that would be a big win. But again... I'm not familiar with the details here; you'd have to test for yourself which is better in your situation.
You can use LINQ:
Dim filePathsSortedByDate = From f In Directory.EnumerateFiles("C:\XmlFiles\")
let fileCreationTime = File.GetCreationTime(f)
Where (Date.Today - fileCreationTime.Date).Days <= 30
Order By fileCreationTime
Select New ListItem(Path.GetFileName(f), f)
Dim files As List(Of ListItem) = filePathsSortedByDate.ToList()
Related
I have tow pages, first one for displaying the data in the text file and the other one is to store the data. I want to save a site in the text file but when i display the data will be just text and I can't click it as a link. The code I post is when I write to a file in display page.
Try
Dim fs As String
fs = Server.MapPath("Footer.txt")
lblsplittext.Text = ""
Dim filestream As StreamReader
filestream = New IO.StreamReader(fs)
Dim readcontents As String = filestream.ReadToEnd()
Dim textdelimiter As String = "#"
Dim splitout = Split(readcontents, textdelimiter)
Dim i As Integer
For i = 0 To UBound(splitout)
lblsplittext.Text &= splitout(i) & "<br>"
Next
filestream.Close()
Catch ex As Exception
Dim str As String
str = ex.Message
End Try
If you have a different suggestion about how to read from a file or database (it doesnt matter from where for now) just keep in mine when i display them i just need to have hyperlinks among my text... Or can I write to html file instead of text file if so what is the difference i need to make to write to html. I really really need help here and i have done many searches but i found nothing.
Thanks in advance.
There are a number of ways you could do this. One would be to use a series of dynamically-added Label controls. Your Hyperlink control could simply be inserted between one Label control and the next.
Do you intend to retrieve information from your series of labels on postback? (It would be redundant to do that, since you already know what the information is, but just in case.) Using multiple controls would make that more complicated. You could try one or more Literal controls, created dynamically and added as child controls to a Panel control. Again, the Hyperlink control would be added at whatever time you need it.
First of all, here comes the load part.
Structure MainStruct
Dim Ans1 As String
Dim Ans2 As String
End Structure
Dim Build As New List(Of MainStruct)
...
...
...
Session("MyData") = Build
The question is how can i read back the contents of the list, stored in the Session?
I mean something like...
Build = Session("MyData")
Instead of Build = Session("MyData").Ans1 you will want to do
Build = CType(Session("MyData"), List(Of MainStruct))
You could also do a DirectCast instead of CType if you want.
Edit: to question change
To then read back the results you will be able to go through Build.
You could loop through it with a for each, a for, some linq, whatever you want!
Since its VB i dont think u need to cast it back, correct me if im wrong.
i dont think u can just do
Build = Session("MyData").Ans1
You need to do something like:
Build = Session("MyData")
then u iterate though ur List<> to access the structs
I'm currently patching an asp.net program where I need to be able to send an image to an SQL Server 2005 DB. It works fine when I use the asp:fileupload control, but the trick is that when the user deletes the image, I'm supposed to replace it with an image from the server saying "empty", in code-behind.
I know how to open, use and save text files in vb, but I can't find any information anywhere on how to open an image / binary file in a similar manner so that I can use it as an sql-parameter on the update query.
Below is an example of how easy it is to use a file from the fileupload control.
Dim t_id As Integer = Convert.ToInt32(Request.QueryString("id"))
open()
Dim picture As New SqlParameter("#picture", pictureFileUpload.FileBytes)
Dim id As New SqlParameter("#id", t_id)
myCommand = New SqlCommand("spChangeImage")
myCommand.CommandType = CommandType.StoredProcedure
myCommand.Connection = conn
myCommand.Parameters.Add(picture)
myCommand.Parameters.Add(id)
myCommand.ExecuteNonQuery()
close()
Now I need a way to open an image file and set it as a parameter in a similar manner, but I've no clue as to how to go about doing that. All the search results are focused on opening and viewing an image in html, I just need the binary to use it in the query. I'm trying to use binaryreader but even then I've no idea how to actually map the file to begin with.
Thanks in advance for any help!
Personally, I wouldn't store this image in the database when the user deletes their value. I would set the column to null. When writing the image I would detect if the column is null, then read the file and write it to the response. If you do this, then you won't need to accumulate anything into a local buffer, you can just write each buffer to the response as it is read. You can use FileInfo.Length to determine the content length of the response.
If you insist on putting the image in the DB, you can also use FileInfo.Length to determine the size of buffer you need to hold the image. Use your BinaryReader to read this length of bytes into the buffer. The buffer then becomes your parameter to the SQL command.
this might help.
How should I go about providing download functionality on an asp.net page to download a series of rows from a database table represented as a linq2sql class that only has primitive types for members (ideally into a format that can be easily read by Excel)?
E.g.
public class Customer
{
public int CustomerID;
public string FirstName;
public string LastName;
}
What I have tried so far.
Initially I created a DataTable, added all the Customer data to this table and bound it to a DataGrid, then had a download button that called DataGrid1.RenderControl to an HtmlTextWriter that was then written to the response (with content type "application/vnd.ms-excel") and that worked fine for a small number of customers.
However, now the number of rows in this table is >10,000 and is expected to reach upwards of 100,000, so it is becoming prohibitive to display all this data on the page before the user can click the download button.
So the question is, how can I provide the ability to download all this data without having to display it all on a DataGrid first?
After the user requests the download, you could write the data to a file (.CSV, Excel, XML, etc.) on the server, then send a redirect to the file URL.
I have used the following method on Matt Berseth blog for large record sets.
Export GridView to Excel
If you have issues with the request timing out try increasing the http request time in the web.config
Besides the reasonable suggestion to save the data on server first to a file in one of the answers here, I would like to also point out that there is no reason to use a DataGrid (it’s one of you questions as well). DataGrid is overkill for almost anything. You can just iterate over the records, and save them directly using HtmlTextWriter, TextWriter (or just Response.Write or similar) to the server file or to a client output stream. It seems to me like an obvious answer, so I must be missing something.
Given the number of records, you may run into a number of problems. If you write directly to the client output stream, and buffer all data on server first, it may be a strain on the server. But maybe not; it depends on the amount of memory on the serer, the actual data size and how often people will be downloading the data. This method has the advantage of not blocking a database connection for too long. Alternatively, you can write directly to the client output stream as you iterate. This may block the database connection for too long as it depends on the download speed of the client. But again; it your application is of a small or medium size (in audience) then anything is fine.
You should definitely check out the FileHelpers library. It's a freeware, excellent utility set of classes to handle just this situation - import and export of data, from text files; either delimited (like CSV), or fixed width.
It offer a gazillion of options and ways of doing things, and it's FREE, and it works really well in various projects that I'm using it in. You can export a DataSet, an array, a list of objects - whatever it is you have.
It even has import/export for Excel files, too - so you really get a bunch of choices.
Just start using FileHelpers - it'll save you so much boring typing and stuff, you won't believe it :-)
Marc
Just a word of warning, Excel has a limitation on the number of rows of data - ~65k. CSV will be fine, but if your customers are importing the file into Excel they will encounter that limitation.
Why not allow them to page through the data, perhaps sorting it before paging, and then give them a button to just get everything as a cvs file.
This seems like something that DLinq would do well, both the paging, and writing it out, as it can just fetch one row at a time, so you don't read in all 100k rows before processing them.
So, for cvs, you just need to use a different LINQ query to get all of the rows, then start to save them, separating each cell by a separator, generally a comma or tab. That could be something picked by the user, perhaps.
OK, I think you are talking too many rows to do a DataReader and then loop thru to create the cvs file. The only workable way will be to run:
SQLCMD -S MyInstance -E -d MyDB -i MySelect.sql -o MyOutput.csv -s
For how to run this from ASP.Net code see here. Then once that is done, your ASP.Net page will continue with:
string fileName = "MyOutput.csv";
string filePath = Server.MapPath("~/"+fileName);
Response.Clear();
Response.AppendHeader("content-disposition",
"attachment; filename=" + fileName);
Response.ContentType = "application/octet-stream";
Response.WriteFile(filePath);
Response.Flush();
Response.End();
This will give the user the popup to save the file. If you think more than one of these will happen at a time you will have to adjust this.
So after a bit of research, the solution I ended up trying first was to use a slightly modified version of the code sample from http://www.asp.net/learn/videos/video-449.aspx and format each row value in my DataTable for CSV using the following code to try to avoid potentially problematic text:
private static string FormatForCsv(object value)
{
var stringValue = value == null ? string.Empty : value.ToString();
if (stringValue.Contains("\"")) { stringValue = stringValue.Replace("\"", "\"\""); }
return "\"" + stringValue + "\"";
}
For anyone who is curious about the above, I'm basically surrounding each value in quotes and also escaping any existing quotes by making them double quotes. I.e.
My Dog => "My Dog"
My "Happy" Dog => "My ""Happy"" Dog"
This appears to be doing the trick for now for small numbers of records. I will try it soon with the >10,000 records and see how it goes.
Edit: This solution has worked well in production for thousands of records.
I want to write some stats to a text file every time a person loads a page. But every once in awhile I am getting at 'Could Not Open File, Already in use' type of error. I can not 100% replicate this error it is very erratic. My code is
Public Sub WriteStats(ByVal ad_id As Integer)
Dim ad_date As String = Now.Year & Now.Month
Dim FILENAME As String = Server.MapPath("text/BoxedAds.txt")
Dim objStreamWriter As StreamWriter
objStreamWriter = File.AppendText(FILENAME)
objStreamWriter.WriteLine(ad_id & ";" & ad_date)
objStreamWriter.Close()
End Sub
My question is, how can I lock and unlock the file so I stop getting the erratic errors?
Thanks
If two or more requests hit your web server at roughly the same time, they will all try to open the same file. You will need to create unique file names for each request.
Public Sub WriteStats(ByVal ad_id As Integer)
Dim ad_date As String = Now.Year & Now.Month
Dim FILENAME As String = Server.MapPath("text/BoxedAds.txt")
Dim index As Integer
Using fs As New IO.FileStream(FILENAME, IO.FileMode.Append, IO.FileAccess.Write, IO.FileShare.ReadWrite), _
tl As New TextWriterTraceListener(fs)
index = Trace.Listeners.Add(tl)
Trace.WriteLine(ad_id & ";" & ad_date)
Trace.Listeners(index).Flush()
Trace.Flush()
End Using
Trace.Listeners.RemoveAt(index)
End Sub
Three important things here:
Use of IO.FileShare.ReadWrite to allow multiple writers on the file at once.
The Using statement to make sure the stream is closed immediately, even if an exception occurs. This will minimize collisions
The TextWriterTraceListener will create a temp file for your if it can't open the file you request, to make sure the message isn't lost.
You will have to handle the exception and build some handling to re-try writing to the file after a short random interval.
If you get too much contention then it might make more sense to log it to a table in a database and create a process to export to a file (if its still needed)
I haven't had any trouble with short info using:
File.AppendAllText(path, info);
Regarding the comment on it causing locks, from reflector it uses the same options explained very well by Joel. It does not use the trace writer, so it won't output to a temp file in the case of high load / large content causing trouble.
If the info is large, you really want separate files. For high load, I would go with Joel's suggestion and create a temp file, which can be alternatively done by catching the exception on File.AppendAllText, and using the same File.AppeandAllText with a unique filename.