Please see part of the code used to save response as a string to resultData variable:
Using response As WebResponse = request.GetResponse()
Dim responseStream As IO.Stream = response.GetResponseStream()
Dim sr As New IO.StreamReader(responseStream)
resultData = sr.ReadToEnd()
It works correctly.
I have one case where the output is a binary file. How can I modify this code to save the reponse as a binary ResultData variable?
Thank you in advance for your support.
There is many ways to do that. This one, is one of those. (This one help you also to show the progress)
However (as advice) to monitoring progress there exists better approaches like Async methods etc.
In the example below I’m going to show you how to save e WebRequest as binary data.
Note that, I’m based on your code and what you want, but, as I said before there exists different better approaches.
'here the file you want to save
Dim LocalFilePath As String = "C:\Users\MyUser\Documents\FolderXYZ\yourfileName.extension"
Using reader As IO.Stream = request.GetResponse.GetResponseStream
Using writer As IO.Stream = New IO.FileStream(LocalFilePath, IO.FileMode.OpenOrCreate, IO.FileAccess.ReadWrite)
Dim b(1024 * 2) As Byte
Dim buffer As Integer = b.Length
Do While buffer <> 0
buffer = reader.Read(b, 0, b.Length)
writer.Write(b, 0, buffer)
writer.Flush()
Loop
End Using
End Using
Related
I have two strings, each string is a PDF etiquette, I must to write this two etiquette into a PDF file. To do this I convert a each string to a byte array (I don't know if this is the best way) and each I Write into a PDF file. When I write one etiquette into PDF file all is good, I see the etiquette, but then I try to appending the second, the result is the same, into the file is only the first etiquette. For example this code write first etiquette and all working good:
Dim fs As FileStream = New FileStream(fullFileName, FileMode.CreateNew)
fs.Close()
fs = New FileStream(fullFileName, FileMode.Append)
Dim str As String = GetPDFString(27)
Dim binaryData As Byte() = ConvertStringToByte(str)
fs.Write(binaryData, 0, binaryData.Length)
fs.Close()
but if I want to append the second etiquette in the same PDF file using this code ... this not appending.
Dim fs As FileStream = New FileStream(fullFileName, FileMode.CreateNew)
fs.Close()
fs = New FileStream(fullFileName, FileMode.Append)
Dim str As String = GetPDFString(25)
Dim str1 As String = GetPDFString(27)
Dim binaryData As Byte() = ConvertStringToByte(str)
Dim binaryData1 As Byte() = ConvertStringToByte(str1)
fs.Write(binaryData, 0, binaryData.Length)
fs.Write(binaryData1, 0, binaryData1.Length)
fs.Close()
both have the same result, and I don't understand why the second etiquette isn't appending? Thank you a lot.
Your question title suggests that you are asking about how to append a byte to a FileStream, not about PDF, and not about Base64 string conversion (which you are using in your code).
Before asking a question on StackOverflow, you need to ensure you are conveying only one problem at a time. Remove everything that is not relevant, and prepare a code sample we can use in a brand new VS project, in order to reproduce your problem and help you solve it.
Now, if your question is really about appending a byte (or a byte array) to a file, it's as simple as one line of code (or two, if you keep FileStream approach). See below link:
C# Append byte array to existing file
Also copy-pasted for your convenience here (and converted from C# to VB.NET):
Dim appendMe As Byte() = New Byte(999) {}
File.AppendAllBytes("C:\test.exe", appendMe)
Or, to avoid memory overflow, if your byte array is expected to be large enough:
Public Shared Sub AppendAllBytes(path As String, bytes As Byte())
'argument-checking here.
Using stream = New FileStream(path, FileMode.Append)
stream.Write(bytes, 0, bytes.Length)
End Using
End Sub
With this line:
fs.Write(binaryData1, binaryData.Length + 1, binaryData1.Length)
Specifically the second argument (binaryData.Length + 1), you're telling it to start appending from the wrong position of binaryData1. If it's 3 bytes long, for example, and so is binaryData, it won't append anything. It should be similar to the first .Write line:
fs.Write(binaryData1, 0, binaryData1.Length)
So it appends all of binaryData1. It will still append it after binaryData - you don't need to specify the length of the preceeding binaryData in this line.
Alternatively, bypassing the above entirely, concatenate your two strings before encoding/writing them to the file:
Dim fs As FileStream = New FileStream(fullFileName, FileMode.CreateNew)
fs.Close()
fs = New FileStream(fullFileName, FileMode.Append)
Dim str As String = GetPDFString(id, token, depot, 25)
Dim str1 As String = GetPDFString(id, token, depot, 27)
Dim binaryData As Byte() = Convert.FromBase64String(str & str1) 'concatenate strings
fs.Write(binaryData, 0, binaryData.Length)
fs.Close()
I'm trying to familiarize myself with network programming, and what better place to start than designing an FTP client code library?
So far I'm not doing very good. I'm trying to create a method which downloads a file from a remote server to a local file path. To do so, all the examples that I could find declare a byte array that serves as a data buffer. I completely understand the point of doing that, rather than reading and writing byte per byte, but I just can't get it to work. Whenever I set a buffer greater than 1 byte, the output is somehow corrupted (different checksums, media files won't play etc).
Can someone please point out what I'm doing wrong here:
Public Function DownloadFile(source As Uri, output As Uri) As FtpStatusCode
Dim request = FtpWebRequest.Create(source)
request.Method = WebRequestMethods.Ftp.DownloadFile
Using response As FtpWebResponse = CType(request.GetResponse, FtpWebResponse)
Using outputStream = New FileStream(output.AbsolutePath, FileMode.Create)
Do
Dim buffer(8192) As Byte
response.GetResponseStream.Read(buffer, 0, buffer.Length)
outputStream.Write(buffer, 0, buffer.Length)
Loop While outputStream.Position < response.ContentLength
End Using
Return response.StatusCode
End Using
End Function
Because this code does work when I set the buffer size to 1, I feel like there's something going wrong with the byte order. But all of this code is synchronous, so how is that even possible...
EDIT
I got it to work now, so here's the code solution for future reference (thanks again #tcarvin):
Public Function DownloadFile(source As Uri, output As Uri) As FtpStatusCode
Dim request = FtpWebRequest.Create(source)
request.Method = WebRequestMethods.Ftp.DownloadFile
Using response As FtpWebResponse = CType(request.GetResponse, FtpWebResponse)
Using inputStream = response.GetResponseStream
Using outputStream = New FileStream(output.AbsolutePath, FileMode.Create)
Do
Dim buffer(8192) As Byte
Dim buffered = inputStream.Read(buffer, 0, buffer.Length).Read(buffer, 0, buffer.Length)
outputStream.Write(buffer, 0, buffered)
Loop While outputStream.Position < response.ContentLength
End Using
End Using
Return response.StatusCode
End Using
End Function
When reading from a stream, you need to capture the return value of the method. Read returns how many bytes were just read. That is the number of bytes you need to then write to your output stream.
I'm trying to set the user agent for a request with XmlRead. I googled a lot about this and couldn't find the answer. Here is my chunk of code:
Dim RssData As DataSet
Dim Title As String
Dim Url As String
Dim Stream As String
Dim buffer As Integer
RssData = New DataSet()
RssData.ReadXml("http://localhost/user_agent.php")
buffer = 0
For Each RssRow As DataRow In RssData.Tables("entry").Rows
Title = Microsoft.VisualBasic.Left(RssRow.Item("title").ToString, 30)
Stream += Title & vbCrLf
Next
LinkLabel3.Text = Stream
For Each RssRow As DataRow In RssData.Tables("entry").Rows
Title = Microsoft.VisualBasic.Left(RssRow.Item("title").ToString, 30)
Url = RssRow.Item("url").ToString
LinkLabel3.Links.Add(buffer, Title.Length, Url)
buffer = buffer + Title.Length + 2
Next
The part of the code that actually performs the web request is buried pretty deep so you'd have to inherit a bunch of code to do what you asked for. Instead, let me suggest a different path, download the XML on your own with code that's easy to set that header, and then load that into the dataset. The WebClient class lets you set arbitrary headers and has a simple DownloadString method. Once you've got that you can wrap it in a MemoryStream and pass that into ReadXml(). (I couldn't find a way to read the XML as a string, that's why I was forced to read it as Stream.)
''//Will hold our downloaded XML
Dim MyXml As String
''//Create a webclient to download our XML
Using WC As New System.Net.WebClient()
''//Manually set the user agent header
WC.Headers.Add("user-agent", "your user agent here")
''//Download the XML
MyXml = WC.DownloadString("http://localhost/user_agent.php")
End Using
''//Create our dataset object
Dim RssData As New DataSet()
''//There is no direct method to load XML as a string (at least that I could find) so we will
''// convert it to a byte array and load it into a memory stream
Dim Bytes As Byte() = System.Text.Encoding.UTF8.GetBytes(MyXml)
Using MS As New System.IO.MemoryStream(Bytes)
''//Load the stream into the reader
RssData.ReadXml(MS)
End Using
''//Your code continues normally here
I am trying to Serialize an object to XML however my object is a generic list containing many records and causes the serializer to consume lots of memory. So I tried to serialize directly to a GZipStream with the following code:
Dim formatter As XmlSerializer = XmlSerializerFactory.GetSerializerForType(_type)
Using _ms As New MemoryStream()
Using gzStream As New GZipStream(_ms, CompressionMode.Compress, True)
_ms.Position = 0
formatter.Serialize(gzStream, obj)
_ms.Position = 0
gzStream.Flush()
gzStream.Close()
End Using
_ms.Position = 0
Dim decompressData() As Byte
Using gzStream As New GZipStream(_ms, CompressionMode.Decompress)
ReDim decompressData(9000 - 1) 'this number doesn't matter, the data in my test sample is small
Dim Len As Integer = gzStream.Read(decompressData, 0, decompressData.Length)
End Using
End Using
However I run into an InvalidDataException The magic number in GZip header is not correct. Make sure you are passing in a GZip stream. when trying to read the data into the decompressData array.
When I Serialize to a separate memory stream first and then compress that stream such as:
Dim formatter As XmlSerializer = XmlSerializerFactory.GetSerializerForType(_type)
Using _ms As New MemoryStream()
Dim uc_fileBytes() As Byte
Dim uc_len As Integer
Using _ms101 As New MemoryStream()
formatter.Serialize(_ms101, obj)
uc_fileBytes = _ms101.GetBuffer()
uc_len = _ms101.Length
End Using
Using gzStream As New GZipStream(_ms, CompressionMode.Compress, True)
_ms.Position = 0
gzStream.Write(uc_fileBytes, 0, uc_len)
gzStream.Flush()
gzStream.Close()
End Using
Dim decompressData() As Byte
Using gzStream As New GZipStream(_ms, CompressionMode.Decompress)
ReDim decompressData(9000 - 1)
Dim Len As Integer = gzStream.Read(decompressData, 0, decompressData.Length)
End Using
End Using
It works fine without error. But why does it fail when I serialize directly to the GZipStream?
The cause of the problem is because the GZipStream behaves differently (obviously) to the MemoryStream when writing to it. It doesn't handle paged writes very well.
In another question here at Stack Overflow, I came across a very helpful code snippet to send code to the Google Closure Compiler, which can minify JavaScript files pretty good.
The problem I'm facing however is that it returns no compiled code in cases I don't expect it to do so.
Code:
This works, i.e. returns minified code:
Dim script = "function test(name) {alert(name);}test('New user');"
This one, on the other hand, does not return anything. The statistics are sent, but no compiled data...:
Dim script = "function test(name) {alert(name);}"
Rest of the code which actually does the work:
Dim Data = String.Format(ClosureWebServicePOSTData, HttpUtility.UrlEncode(script))
_Result = New StringBuilder
_HttpWebRequest = DirectCast(WebRequest.Create(ClosureWebServiceURL), HttpWebRequest)
_HttpWebRequest.Method = "POST"
_HttpWebRequest.ContentType = "application/x-www-form-urlencoded"
'//Set the content length to the length of the data. This might need to change if you're using characters that take more than 256 bytes
_HttpWebRequest.ContentLength = Data.Length
'//Write the request stream
Using SW As New StreamWriter(_HttpWebRequest.GetRequestStream())
SW.Write(Data)
End Using
Dim response As WebResponse = _HttpWebRequest.GetResponse()
Using responseStream As Stream = response.GetResponseStream
Dim encoding As Encoding = System.Text.Encoding.GetEncoding("utf-8")
Using readStream As New StreamReader(responseStream, encoding)
Dim read(256) As Char
Dim count As Integer = readStream.Read(read, 0, 256)
While count > 0
Dim str As New String(read, 0, count)
_Result.Append(str)
count = readStream.Read(read, 0, 256)
End While
End Using
End Using
What could be the casue at all? I'm curious to know.
Possibly using the ADVANCED_OPTIMIZATIONS setting? The function may have been stripped because it is defined, but never used.
check out this page: closure compiler tutorial