A `Monitor` is managed, and more lightweight - but is restricted to your `AppDomain`. A `Mutex` can be named, and can span processes (allowing some simple IPC scenarios between applications), and can be used in code that wants a wait-handle).

For most simple scenarios, `Monitor` (via `lock`) is fine.

A good source of advice on this stuff is the &quot;Threading in C#&quot; by Joseph Albahari. All the content is available online. In my opinion, it&#39;s worth to read [the whole book][1], but yo can check these parts:

 - On [Locking (C# Monitor)][2];

 - On [Mutex][3].

Although it does not cover [.NET 4.0 new parallel constructs][4], it&#39;s a very good starting point.

**Update**: The book has been updated. Now, it covers .NET 4.0 Parallel Programming in its [part 5][5].


  [1]: http://www.albahari.com/threading/threading.pdf
  [2]: http://www.albahari.com/threading/part2.aspx#_Locking
  [3]: http://www.albahari.com/threading/part2.aspx#_Mutex
  [4]: http://msdn.microsoft.com/en-us/library/dd460693%28VS.100%29.aspx
  [5]: http://www.albahari.com/threading/part5.aspx

A Mutex can be shared across processes, and is much more heavy-weight than a Monitor.

Use a Monitor unless you need to synchronize across process boundaries.

I&#39;m using WPFtoolkit `DataGrid` ,I have to wrap text in a `DataGridTextColumn` or 
I have to add a `ToolTip` to the text column.  I have searched the net but i couldn&#39;t get a proper solution.  Expecting your valuable suggestions...

How do I Add a Tooltip To a DataGridTextColumn

`display:none` means that the element isn&#39;t rendered as part of the DOM, so it&#39;s not loaded until the display property changes to something else. 

`visibility:hidden` loads the element, but does not show it. 

Why does jQuery use `display:none` for its show/hide functions instead of switching between `visibility:hidden` and `visibility:visible`?

Why does jQuery show/hide use display:none instead of visibility:hidden?

&gt; **Possible Duplicate:**  
&gt; [What are the differences between various threading synchronization options in C#?](https://stackoverflow.com/questions/301160/what-are-the-differences-between-various-threading-synchronization-options-in-c)  

&lt;!-- End of automatically inserted text --&gt;

What is the difference between a Monitor and a Mutex in C#?

When to use a Monitor and when to use a Mutex in C#?


Monitor vs Mutex in c#

> Possible Duplicate: 
> <a href="https://stackoverflow.com/questions/301160/what-are-the-differences-between-various-threading-synchronization-options-in-c" target="_blank" rel="noopener noreferrer">What are the differences between various threading synchronization options in C#?</a>

What is the difference between a Monitor and a Mutex in C#?
When to use a Monitor and when to use a Mutex in C#?

I&#39;m using OleDb to read from an excel workbook with many sheets. 

I need to read the sheet names, but I need them in the order they are defined in the spreadsheet; so If I have a file that looks like this;


    |_____|_____|____|____|____|____|____|____|____|
    |_____|_____|____|____|____|____|____|____|____|
    |_____|_____|____|____|____|____|____|____|____|
    \__GERMANY__/\__UK__/\__IRELAND__/
    
Then I need to get the dictionary

    1=&quot;GERMANY&quot;, 
    2=&quot;UK&quot;, 
    3=&quot;IRELAND&quot;

I&#39;ve tried using `OleDbConnection.GetOleDbSchemaTable()`, and that gives me the list of names, but it alphabetically sorts them. The alpha-sort means I don&#39;t know which sheet number a particular name corresponds to. So I get;

    GERMANY, IRELAND, UK
    
which has changed the order of `UK` and `IRELAND`. 

The reason I need it to be sorted is that I have to let the user choose a range of data by name or index; they can ask for &#39;all the data from GERMANY to IRELAND&#39; or &#39;data from sheet 1 to sheet 3&#39;.

Any ideas would be greatly appreciated.

if I could use the office interop classes, this would be straightforward. Unfortunately, I can&#39;t because the interop classes don&#39;t work reliably in non-interactive environments such as windows services and ASP.NET sites, so I needed to use OLEDB.

Using Excel OleDb to get sheet names IN SHEET ORDER

I would like to have files named for example:

dd.mm.yyyy.log

How is this possible with log4net?

Log4net rolling daily filename with date in the file name

I have a class with a property which is an enum

The enum is

    /// &lt;summary&gt;
    /// All available delivery actions
    /// &lt;/summary&gt;
    public enum EnumDeliveryAction
      {
        /// &lt;summary&gt;
        /// Tasks with email delivery action will be emailed
        /// &lt;/summary&gt;
        Email,

        /// &lt;summary&gt;
        /// Tasks with SharePoint delivery action 
       /// &lt;/summary&gt;
       SharePoint
      }

When I create an instance of this class, NOWHERE in the code, do I specify the value of the enum field, but it seems to default to the first item in the enumlist, and not a null value, is this how enums work? How is it possible to ensure that the enum gets some kind of null value if it is not set, I don&#39;t want it defaulting to the first value in the enum.


Initial Value of an Enum

is there any measurably performance difference between

    ((TypeA) obj).method1();
    ((TypeA) obj).method2();
    ((TypeA) obj).method3();

and

    var A = (TypeA) obj;
    A.method1();
    A.method2();
    A.method3();

when used alot of times?

I often see something like

    if (((TextBox)sender).Text.Contains(&#39;.&#39;) || ((TextBox)sender).Text.Contains(&#39;,&#39;))

and wonder if this is a waste of performance. 



Performance of TypeCasting

I keep seeing people using doubles in C#. I know I read somewhere that doubles sometimes lose precision. 
My question is when should a use a double and when should I use a decimal type?
Which type is suitable for money computations? (ie. greater than $100 million)

decimal vs double! - Which one should I use and when?

What are the modules used to write multi-threaded applications in Python? I&#39;m aware of the basic concurrency mechanisms provided by the language and also of [Stackless Python][1], but what are their respective strengths and weaknesses?


  [1]: http://www.stackless.com/

Threading in Python

Here&#39;s the Python code to run an arbitrary command returning its `stdout` data, or raise an exception on non-zero exit codes:

    proc = subprocess.Popen(
        cmd,
        stderr=subprocess.STDOUT,  # Merge stdout and stderr
        stdout=subprocess.PIPE,
        shell=True)

`communicate` is used to wait for the process to exit:

    stdoutdata, stderrdata = proc.communicate()

The `subprocess` module does not support timeout--ability to kill a process running for more than X number of seconds--therefore, `communicate` may take forever to run.

What is the **simplest** way to implement timeouts in a Python program meant to run on Windows and Linux?


Using module &#39;subprocess&#39; with timeout

How do you start a thread with parameters in C#?

ThreadStart with parameters

How is ThreadLocal implemented? Is it implemented in Java (using some concurrent map from ThreadID to object), or does it use some JVM hook to do it more efficiently?

How is Java&#39;s ThreadLocal implemented under the hood?

The following code leads to `java.lang.IllegalThreadStateException: Thread already started` when I called `start()` method **second time** in  program.

    updateUI.join();    

    if (!updateUI.isAlive()) 
        updateUI.start();

This happens the **second** time `updateUI.start()` is called.  I&#39;ve  stepped through it multiple times and the thread is called and completly runs to completion before hitting `updateUI.start()`.

Calling `updateUI.run()` avoids the error but causes the thread to run in the UI thread (the calling thread, as mentioned in other posts on SO), which is not what I want.

Can a Thread be *started* only once?  If so than what do I do if I want to run the thread again?  This particular thread is doing some calculation in the background, if I don&#39;t do it in the thread than it&#39;s done in the UI thread and the user has an unreasonably long wait.

Is it legal to call the start method twice on the same Thread?

Does @synchronized not use &quot;lock&quot; and &quot;unlock&quot; to achieve mutual exclusion? How does it do lock/unlock then?

The output of the following program is only &quot;Hello World&quot;.

    @interface MyLock: NSLock&lt;NSLocking&gt;
    @end

    @implementation MyLock

    - (id)init {
        return [super init];
    }

    - (void)lock {
        NSLog(@&quot;before lock&quot;);
        [super lock];
        NSLog(@&quot;after lock&quot;);
    }

    - (void)unlock {
        NSLog(@&quot;before unlock&quot;);
        [super unlock];
        NSLog(@&quot;after unlock&quot;);
    }

    @end


    int main (int argc, const char * argv[]) {
        NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

        MyLock *lock = [[MyLock new] autorelease];
        @synchronized(lock) {
            NSLog(@&quot;Hello World&quot;);
        }

        [pool drain];
    }

How does @synchronized lock/unlock in Objective-C?

I have a process A that contains a table in memory with a set of records (recordA, recordB, etc...)

Now, this process can launch many threads that affect the records, and sometimes we can have 2 threads trying to access the same record - this situation must be denied. Specifically if a record is LOCKED by one thread I want the other thread to abort (I do not want to BLOCK or WAIT).

Currently I do something like this:

    synchronized(record)
    {
    performOperation(record);
    }

But this is causing me problems ... because while Process1 is performing the operation, if Process2 comes in it blocks/waits on the synchronized statement and when Process1 is finished it performs the operation. Instead I want something like this:

    if (record is locked)
       return;

    synchronized(record)
    {
    performOperation(record);
    }

Any clues on how this can be accomplished?
Any help would be much appreciated.
Thanks,

How do determine if an object is locked (synchronized) so not to block in Java?

What does this java code mean? Will it gain lock on all objects of `MyClass`?

    synchronized(MyClass.class) {
       //is all objects of MyClass are thread-safe now ??
    }

And how the above code differs from this one:

    synchronized(this) {
       //is all objects of MyClass are thread-safe now ??
    }


Java Synchronized Block for .class

What is the difference between semaphores and mutex provided by pthread library ?

pthreads mutex vs semaphore

In today’s world where a lot of computers, mobile devices or web services share data or act like hubs, syncing gets more important. As we all know solutions that sync aren’t the most comfortable ones and it’s best not to sync at all.

I’m still curious how you would implement a syncing solution to sync between multiple entities. There are already a lot of different approaches, like comparing a changed date field or a hash and using the most recent data or letting the user chose what he wants to use in a case of a conflict. Another approach is to try to automatically merge conflicted data (which in my opinion isn’t so clever, because a machine can’t guess what the user meant).

Anyway, here are a couple of questions related to sync that we should answer before starting to implement syncing:

 * What is the most recent data? How do I want to represent it?
 * What do I do in case of a conflict? Merge? Do I prompt and ask the user what to do?
 * What do I do when I get into an inconsistent state (e.g. a disconnect due to a flakey mobile network connection)?
 * What do I have to do when I don’t want to get into an inconsistent state?
 * How do I resume a current sync that got interrupted?
 * How do I handle data storage (e.g. MySQL database on a web service, Core Data on an iPhone; and how do I merge/sync the data without a lot of glue code)?
 * How should I handle edits from the user that happen during the sync (which runs in the background, so the UI isn’t blocked)?
 * How and in which direction do I propagate changes (e.g. a user creates a „Foo“ entry on his computer and doesn’t sync; then he’s on the go and creates another „Foo“ entry; what happens when he tries to sync both devices)? Will the user have two „Foo“ entries with different unique IDs? Will the user have only one entry, but which one?
 * How should I handle sync when I have hierarchical data? Top-down? Bottom-up? Do I treat every entry atomically or do I only look at a supernode? How big is the trade-off between oversimplifying things and investing too much time into the implementation?
 * …

There are a lot of other questions and I hope that I could inspire you enough. Syncing is a fairly general problem. Once a good, versatile syncing approach is found, it should be easier to apply it to a concrete application, rather than start thinking from scratch. I realize that there are already a lot of applications that try to solve (or successfully solve) syncing, but they are already fairly specific and don’t give enough answers to syncing approaches in general.

Content Type	Original Author	Original Content on Stackoverflow
Question	Ajay	View Question on Stackoverflow
Solution 1 - C#	Marc Gravell	View Answer on Stackoverflow
Solution 2 - C#	jpbochi	View Answer on Stackoverflow
Solution 3 - C#	Kim Gräsman	View Answer on Stackoverflow

Monitor vs Mutex in c#

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

Why does jQuery show/hide use display:none instead of visibility:hidden?

How do I Add a Tooltip To a DataGridTextColumn

Attributions