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Hey!
If I use a Stream (say MemoryStream), and writes data to this stream with a StreamWriter.
Then if I read data from the same stream at the same time, what happens to the read data?
If I have understood this right then no data is removed from the stream even if it has been read? I have to cal flush to remove all the data.
Is this right?
Is a regular stream from TCP (Network) or File stream working this way? If, how does they handle the readdata?
If I flush after I have read, then the writer could have written some new data that I haven’t readied yet.
Best Regards
SnowJim
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No. A MemoryStream works prety much likle a Text file, but in memory. The data is not removed when read. It just moves the current position pointer to the next character to be read/written.
There is a buffered area in a Stream operation that temporarily holds data being written to the Stream. This data typically isn't written directly to the Stream immediately, kind of like a cache. In order to make sure that the changes (data written) to the stream are finally commited to the stream, you call the .Flush() method.
Now, a Stream only has ONE position pointer. If you write a bunch of data to the stream, you have to position the pointer (seek) to the beginning of the stream is you waht to read all that data. Now, if you don't reposition the pointer back to the end of the data, your next write will overwrite data that you have written, but not read yet.
I think what your doing can be done with methods that are more suited to the task, but I don't remember you posting a specific description of why your going through this trouble.
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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Thanks!
The requirement on ower application is that we have to hand out a stream to the rest of the program.
This means that we have to write to that string and at the same time the other part of the program will have to be able to read from the stream using streamreader.
If we writes 1024 bytes to the stream every time(vary fast) then the other part of the program will probably not manage to keep up with the writer. There will probley be a small buffert all the time.
there by we cant clear the stream in any way.
Its strange that a stream really works like this? It should discard every byte it is reading.
I have seen that there is something cald peak (streamreader), that looks at the next byte with out discarding, this most mean that it will discard when reading from this stream?
What kind of stream is this? Can it really discard when reading?
I have tried to make my own stream, by using an Array List (with FIFO), this works, but the performance is to bad. I am placing one byte at one element, and when it’s readed on position 0 i remove it.
Will i have to do my own stream? And what buffert should I use? If I use a fixed byte array the buffert may run out before the reader have readed there data.
any proposition on my problem?
Best Regards
SnowJim
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Streams do not discard the data as it is read, in general (although as Dave points out, the cursor must be manually positioned to move "backwards" in a stream).
StreamReaders are not streams (they provide utility methods to read streams), and the Peek method of StreamReader looks for the next byte in the stream without moving the cursor forward - that's all.
Is the requirement for your application actually to use a stream, or is it simply to provide some structure where values can be read/written, and where reading equates to removing the read value from the structure? What you seem to be describing is a Queue (not a stream type). The Queue class allows FIFO stacking of objects, which looks like what you want. Dequeued objects are physically removed from the list. Internally, it's a circular array.
The Queue class also provides a synchronized version for thread safety, if that's of any concern.
Alternately, you could develop your own Stream class, and make it do whatever you want.
Hope this helps.
The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' ('I found it!') but 'That's funny...’
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Yes i understand that Streamwriters is not stream but tools to use on streams.
If the data is not discarded in an stream, then the data will eventualy become to big to store in memory. How does streams handle this?
If i use for example a stream with an TCP connection, and writes/reads on this stream, it will never be to big to fit in to the memory what i can se? and i am never using any flush, remove or souch.
Yes i have to provied a Stream from my software, streamreaders will be used on this streams later on. But Queue sounds good, I will probley have use of that in other softwares =)
Best Regards
SnowJim
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As I understand it, a NetworkStream really just wraps a Socket. When Read (or BeginRead) is called on the stream, it actually executes a Receive (or BeginReceive) on the Socket. The NetworkStream itself does not appear to have an intrinsic buffer (byte[]) the way a FileStream does.
NetworkStream actually does its work with unsafe code calls on a Socket below the surface.
If you need to periodically clear the stream, you could do so by just clearing the previously read portion of the stream or something, perhaps by reading the as-yet-unread portion of the buffer into memory, then creating a new stream with only that data (or as suggested before, implement your own stream for doing it), but either way, it may be important to synchronize your stream writing code and possibly your reading code when such an even occurs - you could lock the stream, clear the read portion, raise an event that it's been truncated, and unlock it.
Hope this helps.
The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' ('I found it!') but 'That's funny...’
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Yes i have tryed to build my own stream there i use an ArrayList. Every Element is storing one byte, and this is not a good ide, ArrayList is to slow.
Then i thougt if i just use e memoryStream in side my stream, but then i have to synchronize as you say so i delet some readed date and during this deletion i will have to lock the memoryStream.
But if i have under stod it right i cant just delet some bytes in a memory stream, insted a vill have to use flush or somthing like that to remove the stream, and in this case all data will disipare.
Best Regards
SnowJim
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As you have no-doubt discovered, storing an ArrayList of bytes is not a good idea (at least with the goal of reinventing a Stream).
Flush does not cause all the data to disappear. It ensures that any bytes in the buffer are written to some device (at least that's the principal, although inheritors of Stream are free to implement it as they wish). In the case of MemoryStream, Flush is overridden to do nothing at all, since there is no known "device".
You're right. I don't know of any way to arbitrarily delete bytes in a stream, but as I suggested, you could just lock the stream, read the bytes you want to save from the stream (those not already read by the client) into a local byte[], then reinitialize the stream with those bytes and synchronize the reader and writer with the new position, length etc.
The most exciting phrase to hear in science, the one that heralds the most discoveries, is not 'Eureka!' ('I found it!') but 'That's funny...’
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dear friends,
i am writing a virtual keyboard and i want to know in what commands do i need to use in
order to write to an external text environment when a specific button is being clicked?
thank u 4 your time.
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Define "external text environment".
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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notepad, word or any other editor.
like the microsoft virtual keyboard.
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Can someone please help me with the following code?? I am basically trying to read from an Xml file and display text from that file into a textbox. Everything is ok except for trying to add the text to the textBox.Text i get an error and I don't know why. Are there any books that you would recommend for better understanding windows forms??
Error is:
WindowsApplication1.Form1.textBox1 denotes a field where a class was expected.
the line that causes the error is:
textBox1.Text = (reader.ReadString());
Here is the full code:
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.IO;
using System.Xml;
namespace WindowsApplication1
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.TextBox textBox1;
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent call
//
}
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.textBox1 = new System.Windows.Forms.TextBox();
this.SuspendLayout();
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point(48, 48);
this.textBox1.Multiline = true;
this.textBox1.Name = "textBox1";
this.textBox1.Size = new System.Drawing.Size(656, 224);
this.textBox1.TabIndex = 0;
this.textBox1.Text = "text";
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(760, 350);
this.Controls.Add(this.textBox1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
#endregion
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
ProcessTest();
}
static void ProcessTest()
{
XmlTextReader reader = new XmlTextReader("c:\\testcj.xml");
while (reader.NodeType != XmlNodeType.EndElement && reader.Read())
{
if (reader.NodeType == XmlNodeType.Element)
{
switch (reader.Name)
{
case "question":
textBox1.Text = (reader.ReadString());
reader.Read();
break;
case "answer":
reader.Read();
break;
}
}
}
}
}
}
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Hi,
Just take a look at the code, where you have defined a Static medthod ProcessTest...
in this method jour textbox1 control is out of scope.. -Jou can not use it in this way..
My suggestion to you as changes is...
ProcessTest(); ..should be removed from the main to be just after InitializeComponent();
static void ProcessTest() //change the keyword static to public.
-You should read more about 'member access modifiers' such as static private public ....
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OMG, such a simple change and it works perfectly. Thanks a lot Besinci you have saved me a great deal of frustration. Do you know of any good reading material for working with windows forms?
Thanks again.
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Any book on VB.NET. There's tons of them.
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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I need to develop an application that manipulate browser actions. as in it could open a browser and through interaction to the application the application interacts with the browser (preferably IE) and functions. where can i look for info on how to do this? thanks.
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 Wait for the 2005 vs and the new webbrowser control.
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so until then there is no way for me to create an app in C# that will control and automate tasks in the browser for me?
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What do you mean by "automate tasks"? You can add a web browser control to your app in 2003. You need to add a control to the Toolbox, a COM component called Microsoft Web Controls (C:\windows\system32\shdocvw.dll). You can then drop one on your form. This will give you an instance of IE on your form that you can use.
But, like a said before, everything else depends on what you mean by "automate tasks"...
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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Basically i want the app to interact with a web page. to have it fill out entry forms on the web page using predetermined data in the app. it will have to do it automatically. such that when the app is started it would open that webpage, fill out a textbox and then have the webpage submit it. all without the user doing anything. is that possible?
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You can do this without actually "showing" the webpage on the screen, if that can help. I don't remember the exact class names, but search MSDN for "HTML POSTING", you should find something.
With those classes, you can also maintain a session and cookies.
HTH
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I dont know if i was just looking in the wrong place on MSD for that or if it isnt what i need. I am at the point where i can open the browser from my app, but then i want it to find an html form field such as
<br />
<input name=user type=text><br />
and put some data in it
then find the
<br />
<input type=submit value=find user><br />
and "click" it.
is that something the HTML post can do? i mean i know it should be able to be done, i just can't find where to look to find out how. i hope i've cleared this up, does anyone know what i'm looking for????
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Hi everyone, I would like to make a small program which add a key to a specified path in the regiser if it doesn't exist, and deletes it if it exists. How do I write or search the register? Win XP
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Add to your code :
using Microsoft.Win32;
at the top.
And inside it you will find all what you need.
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