C# Discussion Boards - CodeProject

5-Oct-02 8:19

I hope anyway!

I want to do (for example):

StreamReader sr;<br />
if (cond1)<br />
  sr = new StreamReader(@"C:\temp.txt");<br />
<br />
// some code<br />
for (int i = 0 ; i < 100 ; i++)<br />
{<br />
if (cond1)<br />
  sr.WriteLine("{0},{1}",v1,v2);<br />
}<br />
<br />
if (cond1)<br />
  sr.Close()

but the compiler flags up (sr) as unassigned. Frown | :(

What's the easy way out of this?

Rgdz

B.

Paul Riley5-Oct-02 10:38

Paul Riley

5-Oct-02 10:38

Why are you writing to a StreamReader?

My guess is that you really want a StreamWriter and because the file doesn't exist, new StreamReader(...), it's returning null.

Paul

Barry Lapthorn5-Oct-02 11:10

5-Oct-02 11:10

Oops, sorry typo. I wish that was the problem!

The trouble is I only want to use the StreamWriter (!!) if a certain condition is true. Otherwise, don't use it. Since C# uses references, if I don't declare it, the compiler flags it as null regardless of what conditional it's inside Frown | :(

In C++ I could do:

Writer* pWriter;<br />
if (cond1)<br />
  pWriter = new Writer;<br />
<br />
if (cond1)<br />
  pWriter->WriteLine()<br />
<br />
// etc.

without any trouble, which is what I'm trying to achieve in C#

Rgdz

B.

Paul Riley5-Oct-02 11:22

Paul Riley

5-Oct-02 11:22

Barry Lapthorn wrote:
Oops, sorry typo. I wish that was the problem!

Laugh | :laugh:

Well, you said it was simple.

If I'm understanding you correctly, I think this might help.

You can set a StreamWriter to StreamWriter.Null which does all the work for you. You can write to it as much as you like and it all just disappears into Bill Gates ass (or something like that Laugh | :laugh:

).

Paul

Barry Lapthorn5-Oct-02 12:24

5-Oct-02 12:24

Almost but I want it for a generic object as well. I think the next item in the thread answers it.

I'm a C# noob I'm afraid Wink | ;)

Paul Riley5-Oct-02 12:30

Paul Riley

5-Oct-02 12:30

Sorry, yeah, I missed the point completely again. My biggest fault is always looking for something bigger than it actually is. I should have read the bit about assignment a bit more carefully Smile | :)

I'd still advise using StreamReader.Null [edit]StreamWriter.Null, duh![/edit] purely because it means you don't have to worry again about whether it's null or not.

Paul

Barry Lapthorn5-Oct-02 12:47

5-Oct-02 12:47

I wasn't exactly on top form either as the compiler error message does actually say that the variable was unassigned/undefined! Which tells you that you should set it to something. Doh!

Blush | :O

Thanks

Barry

leppie5-Oct-02 13:54

leppie

5-Oct-02 13:54

Paul Riley wrote:
My guess is that you really want a StreamWriter and because the file doesn't exist, new StreamReader(...), it's returning null

Laugh | :laugh:

I didnt even see that!

Before you criticize a man, walk a mile in his shoes. That way, when you do criticize him, you'll be a mile away and have his shoes.

leppie5-Oct-02 11:28

leppie

5-Oct-02 11:28

StreamReader sr = null;

That should the compiler behave Smile | :)

null is an assignment.

Give them a chance! Do it for the kittens, dear God, the kittens!
As seen on MS File Transfer: Please enter an integer between 1 and 2.

Barry Lapthorn5-Oct-02 12:26

5-Oct-02 12:26

Ah ha! That solves my problem.

I'm just getting started on C#. I should have realised that straight away though!! Wink | ;)

Thanks.

B.

Microsoft Installer

Alex Korchemniy5-Oct-02 6:30

Alex Korchemniy

5-Oct-02 6:30

Using the setup template, that came with VS.NET, I successfully created an installer for my application. Behind the scenes, it creates two seperate user interface sets. One for the admin and one for the normal users. I have a few bugs in the 'normal users' installation.

How do I limit the installation to allow only administrators to install the application?

Im sure someone knows. Thanks in advance.

Re: Microsoft Installer

Alex Korchemniy5-Oct-02 13:28

Alex Korchemniy

5-Oct-02 13:28

I found a solution! Here it is:

First, download the MSI sdk, and Install it. Then install Orca. Orca is used to edit the setup database tables. Open the msi package in orca. Go the the Control Conditionals table and set a conditional disable to the next button on the Welcome page. Also add another string to explain that admin rights are needed (Added to the controls table). Set a conditional show and hide on the text strings.

The result:

When a normal user tries to install the can only click on exit.
When admin tries to install they can click next and go on.

I hope this helps someone. Orca is very cool. Can be complex to use, but very cool nevertheless.

Smile | :)

Re: Microsoft Installer

David Stone6-Oct-02 11:53

David Stone

6-Oct-02 11:53

Is it better than the MSI projects in VS.NET? I have a couple MSI projects and was wondering if there was a benefit to using Orca and the SDK instead of just VS.NET.

Norm Almond: I seen some GUI's in my life but WTF is this mess
Leppie: I made an app for my sister and she wouldnt use it till it was colorful enough
Norm:good point leppie, from that statement I can only deduce that this GUI must be aimed at children
Leppie:My sister is 25
-Norm on the MailMagic GUI

Asynchronous Streams?

ez25-Oct-02 6:19

ez2

5-Oct-02 6:19

I've been playing with asynchronous streams and have a question. When I use the beginRead method for asynchronous reading, the for loop in the code below never gets called until the entire file(fairly large) is completely read(ie. mutiple begin reads and callbacks). I thought that the code should process the for loop while doing some reading of the file and when the read completes right it to the screen. This continues until the entire file is read thereby alternating the output from the for loop and the reading of the file. This is not occuring for me. Is there something I'm missing? I've tried this numerous times using different types of streams and the same thing occurs. Code snippet below:

FileStream inputStream; // inputStream is a filestream

public void Run()
{
inputStream.BeginRead(buffer,0,buffer.Length,new AsyncCallback(this.Callback),null);

for(long i = 0; i <500000; i++)
{
if(i%10000 ==0)
Console.WriteLine(i.ToString());
}
}

public void Callback(IAsyncResult ar)
{
int bytesRead = inputStream.EndRead(ar);
// write output to screen
}

Non Rectanglular forms

Nnamdi Onyeyiri5-Oct-02 4:31

5-Oct-02 4:31

does anyone know where to start?

1001111111011101111100111100101011110011110100101110010011010010
Sonork | 100.21142 | TheEclypse

Furty5-Oct-02 4:45

Furty

5-Oct-02 4:45

Maybe this[^] can help..

Nnamdi Onyeyiri5-Oct-02 4:54

5-Oct-02 4:54

thanks, looks just like wat i need.

1001111111011101111100111100101011110011110100101110010011010010
Sonork | 100.21142 | TheEclypse

David Stone5-Oct-02 14:10

David Stone

5-Oct-02 14:10

An MSDN search gave me this as the first result:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dv_vstechart/html/vbtchShapedWindowsFormsControlsInVisualStudioNET.asp[^]

And that wasn't even with Google...that was with MSDN's crappy built-in search. C'mon Nnamdi, we gotta do all your thinking for you? Wink | ;)

Norm Almond: I seen some GUI's in my life but WTF is this mess
Leppie: I made an app for my sister and she wouldnt use it till it was colorful enough
Norm:good point leppie, from that statement I can only deduce that this GUI must be aimed at children
Leppie:My sister is 25
-Norm on the MailMagic GUI

Nnamdi Onyeyiri5-Oct-02 23:29

5-Oct-02 23:29

your damn straight, why should i do any research, wheni have you here to do it for me Poke tongue | ;-P

Besides, i had more important things to do yesterday.

1001111111011101111100111100101011110011110100101110010011010010
Sonork | 100.21142 | TheEclypse

David Stone6-Oct-02 11:45

David Stone

6-Oct-02 11:45

Nnamdi Onyeyiri wrote:
Besides, i had more important things to do yesterday.

OMG | :OMG:

More important things to do than programming!?!?! You've lost your mind! Big Grin | :-D

Nnamdi Onyeyiri6-Oct-02 20:12