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I saw this code
public class MyClass
{
protected static string a = "a";
public void DoStuff()
{
lock (a)
{
}
}
}
why not
public class MyClass
{
public void DoStuff()
{
lock (this)
{
}
}
}
CodingYoshi
Artificial Intelligence is no match for Human Stupidity.
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Why would you lock an entire class when you are just working on a single object inside of the class? What if somebody else wants to work on a different part of it?
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What if the method is changing a data member which is also used in another method? I guess it will be locked for that method as well, right? But why a static variable? I looked at the class and looks like it is only used for this purpose
CodingYoshi
Artificial Intelligence is no match for Human Stupidity.
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There is only one a inside that class, however there could be many instances of that class; lock(a) is a lock shared by all instances, lock(this) isn't. Which one it should be depends on the data used inside the lock, is it instance-specific or is it global?
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Good answer. I missed the fact that a is static.
Martin Fowler wrote: Any fool can write code that a computer can understand. Good programmers write code that humans can understand.
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Ok so lock (this) means lock the calling object for the duration of the code block. lock(a) means lock a for the duration of the code block which means other threads still have access to the object just not a, am i right?
CodingYoshi
Artificial Intelligence is no match for Human Stupidity.
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the terminology may be a little confusing, this is how I explain it:
1.
every instance of lock(lock-object), all sharing the same lock-object, restricts access to whatever code is inside the lock's code block, in such a way that only one thread can get passed the lock-block's entry point. Once a thread has succeeded entering such code block, all other threads trying to enter the same lock-block (or some other lock-block on the same lock-object) will be stalled until the former leaves its lock-block, and only then one of the others is allowed to proceed.
2.
So the lock-object is like a key that fits every lock statement that refers to it; the key is unique, there is only one of it (for a given lock-object), and initially it is available to everyone; the first thread to reach a lock statement grabs the key, and can proceed; he must relinquish the key when leaving the lock-block; in the mean time the other threads, encountering a lock, would have to wait for the key to become available.
3.
locks only make sense when you have more than one thread (warning: a lot of asynchronous events, such as a network's DataReceived, would execute on different threads).
4.
using locks correctly isn't easy for the novice; with too much locking, you may cripple the app's performance and the user experience, ultimately the app could come to a halt ("dead-lock"). With insufficient locking all may seem fine, until suddenly weird things start to happen, e.g. wrong results getting generated as some object gets into an unexpected state, when one thread changes one state variable, while another thread changes another, resulting in some inconsistencies.
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Great and thanks for the explanation, definitely clears things up. I know how threads work but the part which confused me was the static part.
CodingYoshi
Artificial Intelligence is no match for Human Stupidity.
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you're welcome.
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Because you don't want to expose a public member that other classes can put a lock on. It could lead to a deadlock, as with this example (you will never see "Done"):
public class MyClass
{
private Action<MyClass> action;
public MyClass(Action<MyClass> action)
{
this.action = action;
}
public void DoStuff()
{
MessageBox.Show("Started");
lock (this) { action(this); }
MessageBox.Show("Done");
}
}
(new MyClass(delegate(MyClass instance) {
var t = new System.Threading.Thread(delegate()
{
lock (instance) { }
});
t.Start();
t.Join();
})).DoStuff();
Martin Fowler wrote: Any fool can write code that a computer can understand. Good programmers write code that humans can understand.
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From the documentation[^]:
"
In general, avoid locking on a public type, or instances beyond your code's control. The common constructs lock (this), lock (typeof (MyType)), and lock ("myLock") violate this guideline:
lock (this) is a problem if the instance can be accessed publicly.
lock (typeof (MyType)) is a problem if MyType is publicly accessible.
lock(“myLock”) is a problem since any other code in the process using the same string, will share the same lock.
Best practice is to define a private object to lock on, or a private static object variable to protect data common to all instances.
"
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First don't use string literals as a locking mechanism. Basically it doesn't work the way you think it does (regardless of all other issues.)
Second the semantics of your examples are different. In one case you are using a class level (static) and in the other you are using a instance level lock.
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First don't use string literals as a locking mechanism. Basically it doesn't work the way you think it does
Please elaborate and explain
CodingYoshi
Artificial Intelligence is no match for Human Stupidity.
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String literals are global to the application.
Thus the following represents one locking object instance regardless of the number of class instances for either class. (And the examples specifically do not use static.)
class A
{
private String lockObject = "a";
public void Doit()
{
lock(lockObject) {...}
}
}
class B
{
private String lockObject = "a";
public void Doit()
{
lock(lockObject) {...}
}
}
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What is the best way to make application Multi Language ?
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That's kinda what I said. 
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Find all "messages" shown to the user (in message boxes, labels, forms, ...). Give short names to those messages, put both the short name and the original text into a resource file, then grab the text from the resource file for the "short name" where ever something is to be shown to the user. The resource file can be translated by specialized companies. The entries there look something like:
<data name="IndentDlg_btnOK_Text" xml:space="preserve">
<value>&OK</value>
</data>
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hi
how to convert my C# winform program to service program ?
i need that my program will work like service (like listener)
thanks in advance
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The best way is to start a new Windows service project and move the code from the winforms app to the servuice app. In case you weren't aware, a windows service can't have any forms in it.
".45 ACP - because shooting twice is just silly" - JSOP, 2010
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You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
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"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997
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I add an ocx control on my form (right click on toolbox->choose item ->select special .ocx->add it on form) and work correctly. then i make setup for my project and add .ocx file to my setup project but when i install setup on destination computer this .ocx control doesn't work
why ?
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Try registering it with regsvr32 and see if that cures it.
Regards,
Rob Philpott.
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