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Hello,
Please someone explain to me which is the need of Sychronized and SyncRoot in .NET collections. Why and how should I use this two features. Aren't the collections thread safe?? And if them aren't, a lock is not enough? Really, I think I have a big missunderstood about collections, please help.
Thanks,
Miguel
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I'm not expert here, but here is my understanding.
I believe most of the collections have the SyncRoot element, and when you are locking the collections you need to lock the SyncRoot element.
So if you are locking a hastable, it should look something like
lock(myhashtable.SyncRoot).
The locking keyword in c# is a bit misleading, actually what it does is grant you access to the lock, so that no other thread can acquire the lock until you release it.
regards
Kannan
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Don Miguel wrote:
which is the need of Sychronized
Synchronized tells you if the collection's operations will be thread-safe. Generally this is done by implementing a wrapper around the collection, using a lock on the SyncRoot for each operation performed.
Don Miguel wrote:
which is the need of SyncRoot
SyncRoot is for doing your own locking. Say you need to add a lot of items to the collection, during which no other thread should use it. Rather than using the Synchronized wrapper which would lock/unlock for each operation you would create a lock on the SyncRoot object, then perform each of your operations.
Don Miguel wrote:
Aren't the collections thread safe??
No, you need to refer to the documentation for each class you wish to use to find out if the operations are thread-safe. Making everything thread-safe by default is expense CPU wise, so you are better off not putting it in for the cases where thread-safety isn't an issue.
Most collection classes expose some way of getting a Synchronized version, usually by a static method of some sort. Always check the documentation to be sure.
James
"It is self repeating, of unknown pattern"
Data - Star Trek: The Next Generation
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Many thanks James!
You was very explicit, it helps me much.
Don Migule
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Hello,
How do I share data in my DLL with with other DLLs?
Chito
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I think I have come across a fairly common situation but I cant find any help with this.
I have a simple form with 2 controls. A text box (Employee's Name) and a combo box (Employee's Job Title). I have a DataTable that I have tied both the text box and combo box to. Changing positions using the CurrencyManager works fine and everything is good.
But now I want to populate the combo-box with a list of all available jobs. I want to be able to select a item from the list and have it update the appropriate row in my DataTable as would an edit within the text box.
I have the following code, but I get un-expected results.
<br />
DataTable jobs = new DataTable("Jobs");<br />
jobs.Columns.Add("Job", typeof(string));<br />
jobs.Rows.Add(new object[] {"Software Engineer"});<br />
jobs.Rows.Add(new object[] {"Project Manager"});<br />
jobs.Rows.Add(new object[] {"Tester"});<br />
jobs.Rows.Add(new object[] {"Documenter"});<br />
jobs.Rows.Add(new object[] {"Project Lead"});<br />
<br />
cboJob.DataSource = t;<br />
cboJob.DisplayMember = "Job";<br />
<br />
DataTable namesAndJobs = new DataTable("NamesAndJobs");<br />
namesAndJobs.Columns.Add("Name", typeof(string));<br />
namesAndJobs.Columns.Add("Job", typeof(string));<br />
<br />
namesAndJobs.Rows.Add(new object[] {"Bob", "Project Lead"});<br />
namesAndJobs.Rows.Add(new object[] {"Mark", "Documenter"});<br />
namesAndJobs.Rows.Add(new object[] {"Henry", "Project Manager"});<br />
<br />
txtName.DataBindings.Add("Text", namesAndJobs, "Name");<br />
cboJob.DataBindings.Add("Text", namesAndJobs, "Job");<br />
Can what I want to do, even be done? If not, what is the purpose of allowing multiple DataBindings to the same control?
"I am so smart. S-M-R-T. I mean, S-M-A-R-T" - Homer
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I was wondering how I would center the form when it loads? In VC++ and VB I believe there is a setting to center the form. But I don't see it in the properties. So the other way I was planning on doing this was to do something similar to
Form.Left = (Screen_Width+Form_Width/2)
for the width and height, but for that I need to know how to get the screen width.
Any help on either method or another one will be much appreciated.
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I found it.
// Center the Form on the user's screen everytime it requires a Layout.
this.SetBounds((Screen.GetBounds(this).Width/2) - (this.Width/2),
(Screen.GetBounds(this).Height/2) - (this.Height/2),
this.Width, this.Height, BoundsSpecified.Location);
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I don't know your specific circumstance but this code will always keep the form centered in the screen. This may or may not be desirable, personally I'd find it far too annoying to even use your app anymore.
To center a form on the screen at startup, set the StartupPosition property of the Form to FormStartupPosition.CenterScreen.
Even better is to do the above the first time the app is run, then store user preferences so they don't have to keep resizing/moving the form everytime they run your app.
Of course I don't know your circumstances so you may have a good reason for doing so (kiosk, controller, etc.).
James
"It is self repeating, of unknown pattern"
Data - Star Trek: The Next Generation
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Is there a way to differentiate between an event that is fired from the mouse vs. programmatically...??? For example, I need to be able to differentiate between a mouse clicking a treeview checkbox vs. my code setting a checkbox.
If you set a checkbox in the code with this statement:
"node.Checked = e.Node.Checked;"
it triggers the treeview AfterCheck event, just as if you'd clicked it with the mouse.
I only want the event to be fired from a mouse click... is there a way to do this?
thanks.
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A scenario I've used is with a global variable:
private bool m_ProgClick = false;
public void Foo()
{
...
m_ProgClick = true;
node.Checked = e.Node.Checked;
m_ProgClick = false;
...
}
protected void OnClick(...)
{
if (!m_ProgClick)
{
}
}
I've also used a stack to implement multiple places in the code that need to bypass the Click event (or other similar types of events). Write me if you want the details.
α.γεεκ Fortune passes everywhere.
Duke Leto Atreides
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Try this:
private void treeView1_AfterCheck(object sender, System.Windows.Forms.TreeViewEventArgs e)
{
if (e.Action == TreeViewAction.ByMouse)
{
MessageBox.Show("ByMouse");
}
}
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Try digging into the event arguments that are passed to you.
e.something may identify that a mouse click occured. That way
your coding is based off what is passed to you in the event and
you become independant of internal code.
_____________________________________________
The world is a dangerous place.
Not because of those that do evil,
but because of those who look on and do nothing.
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Please. I need to do a search for the not less or greater key than a specific value and using System.Collections like Hashtable, SortedList, ... in the same way as using STL map upper_bound and lower_bound functions. How could I do?
Thanks.
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Same problem !!!
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// Structs can be declared as arrays
// So can classes.
// But the classes don't work correctly?
using System;
namespace ConsoleApplication1
{
public struct myStruct
{
public int i;
}
public class myClass
{
public int i;
}
class Class1
{
static void Main(string[] args)
{
// WORKS OK
myStruct[] my_struct = new myStruct[10];
my_struct[0].i = 10;
// DOESN'T WORK
myClass[] my_class = new myClass[10]; // Can see the arrayed object in the Autos window...
my_class[0].i = 10; // error ... :
// An unhandled exception of type 'System.NullReferenceException'
// occurred in ConsoleApplication1.exe
// Additional information: Object reference not set to an instance of an object.
}
}
}
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The classes do work correctly, just different.
If you create an array of a struct object, you get literally that, an array of that object. If you create an array of a class object, you get an array of references which all initialize to null.
You need to create the objects seperately (ie. my_class[0] = new myClass();) before you set the property.
Paul
We all will feed the worms and trees
So don't be shy - Queens of the Stone Age, Mosquito Song
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Thanks. I tried the identical thing for 2 hours but it wouldn't work.
Putting your sample in that example I gave, works.
I dont' know why my previous thing didn't work.
I will try to reproduce the error again and repost it. I suspect an IDE/compiler bug and/or an incorrect error message text from the compiler.
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I need to analyse an entire Software-Package with a Database and Source-Code. So I'm looking for a Software to document the Software-Package Source Code and the Database; Which variables are used in which programm and which methodes are available and where to find them, what are the fieldnames in a database table...and so on.
Does anybody know a good Documentation-Software and where to get it?
Thanks
Stefan
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this is basic but important.
VS.NET and .NET lang provides XML script document. you can create and write scripts in your programs and then after generate the document. this is xml output..
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I have a .NET dll with some Windows Forms Control in it, and a .NET exe that uses a control in the dll.
How should I do to compile/join them into a SINGLE EXE, without the dll source?
Thanx.
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Assembly Linker, look for al.exe in your SDK\bin directory.
I rated this article 2 by mistake. It deserves more. I wanted to get to the second page... - vjedlicka 3:33 25 Nov '02
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AL cannot "join" exe and dll.
thanks anyway, any other idea?
What AL.EXE Does Not Do
While shipping two closely related but separate DLLs is not that much of a bother, it would be nice if, since they are so closely intertwined, we could merge the two different assemblies into one. The ability to merge multiple libraries together would simplify deployment in many cases; applications that use many different languages or large applications written in the same language but built upon many different projects would benefit from single-assembly deployment.
You might, at this point, expect me to introduce AL.EXE (assembly linker) as the utility that can link multiple modules into a single file for deployment. While many developers new to .NET believe this is what AL.EXE does (and the MSDN seems to imply that this is what AL.EXE does) that is actually not the case. It is true that you can use AL.EXE to create a new assembly DLL that seems to combine two or more assemblies into one with the command line command:
al CSharpClass.netmodule VBClass.netmodule /target:library /out:combo.dll
(NOTE: don't worry about the "netmodule" extension just yet, we will discuss it in a moment. For the moment, pretend that the netmodule keyword is simply a DLL extension)
You can then take a client application that requires both classes (CSharpClass and VBClass) and link it only to combo.dll such that we can have:
csc client.cs /r:combo.dll
as opposed to:
csc client.cs /r:VBClass.dll /r:CSharpClass.dll
However, this may lead the developer to believe that he has combined the two assemblies into one, and he can simply ship combo.dll with his client, and not including VBClass.dll or csharp.dll. But this is not the case. In fact, the developer must now ship combo.dll AND CSharpClass.netmodule and VBClass.netmodule, otherwise his application will not run.
We can see then, that while AL.EXE might make our compilation simpler, it does not really save us anything from a deployment perspective. So what is AL.EXE good for? The answer is for working with what are known as modules and compiling them into an assembly. We will see in the section after next, modules come into play heavily when we are writing international applications.
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Ahh, remebered there was a catch, what you can use though is ILLinker available on GotDotNet  Works like a charm.
I rated this article 2 by mistake. It deserves more. I wanted to get to the second page... - vjedlicka 3:33 25 Nov '02
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