[According to Microsoft Docs][1], since .NET 4.5 The following instance methods **are thread safe** (thanks @ischell):

    CancelPendingRequests
    DeleteAsync
    GetAsync
    GetByteArrayAsync
    GetStreamAsync
    GetStringAsync
    PostAsync
    PutAsync
    SendAsync
    PatchAsync


  [1]: https://docs.microsoft.com/en-us/dotnet/api/system.net.http.httpclient#remarks

Here is another [article][1] from Henrik F. Nielsen about HttpClient where he says:

&quot;*The default HttpClient is the simplest way in which you can start sending requests. **A single HttpClient can be used to send as many HTTP requests as you want concurrently** so in many scenarios you can just create one HttpClient and then use that for all your requests.*&quot;

  [1]: https://docs.microsoft.com/en-us/archive/blogs/henrikn/httpclient-httpclienthandler-and-webrequesthandler-explained

Found one [MSDN forum post][1] by Henrik F. Nielsen (one of HttpClient&#39;s principal Architects).  

Quick summary:  

* &gt; If you have requests that are related (or won&#39;t step on eachother) then using the same HttpClient makes a lot of sense.

* &gt; In genral I would recommend reusing HttpClient instances as much as possible.


  [1]: http://social.msdn.microsoft.com/Forums/en-US/netfxnetcom/thread/4e12d8e2-e0bf-4654-ac85-3d49b07b50af/

I have two t-sql queries using SqlServer 2005. How can I measure how long it takes for each one to run? 

Using my stopwatch doesn&#39;t cut it.

Measure the time it takes to execute a t-sql query

I have a situation where I want a bash script to replace an entire line in a file.
The line number is always the same, so that can be a hard-coded variable.

I&#39;m not trying to replace some sub-string in that line, I just want to replace that line entirely with a new line.

Are there any bash methods for doing this (or something simple that can be thrown into a .sh script).

How to replace an entire line in a text file by line number

In all the examples I can find of usages of `HttpClient`, it is used for one off calls. But what if I have a persistent client situation, where several requests can be made concurrently? Basically, is it safe to call `client.PostAsync` on 2 threads at once against the same instance of `HttpClient`.

I am not really looking for experimental results here. As a working example could simply be a fluke (and a persistent one at that), and a failing example can be a misconfiguration issue. Ideally I&#39;m looking for some authoritative answer to the question of concurrency handling in HttpClient.

Is HttpClient safe to use concurrently?

<p>In all the examples I can find of usages of <code>HttpClient</code>, it is used for one off calls. But what if I have a persistent client situation, where several requests can be made concurrently? Basically, is it safe to call <code>client.PostAsync</code> on 2 threads at once against the same instance of <code>HttpClient</code>.</p>
<p>I am not really looking for experimental results here. As a working example could simply be a fluke (and a persistent one at that), and a failing example can be a misconfiguration issue. Ideally I'm looking for some authoritative answer to the question of concurrency handling in HttpClient.</p>


I am converting a string like &quot;41.00027357629127&quot;, and I am using;

    Convert.ToSingle(&quot;41.00027357629127&quot;);

or

    float.Parse(&quot;41.00027357629127&quot;);

These methods return *4.10002732E+15*.

When I convert to float I want &quot;41.00027357629127&quot;. This string should be the same...


Converting String To Float in C#

I&#39;d like to know if there are effective and open source tools to develop C# applications on Linux (Ubuntu). In particular, I have to develop Windows Forms applications.

I know about the **[Mono][1] project**, but I&#39;ve never used it. What are the best tools (IDE, compiler, etc.) to set up a .NET developing environment on Ubuntu?

Is software developed on Linux runnable on Windows? Are there different behaviors or incompatibilities?

  [1]: https://en.wikipedia.org/wiki/Mono_%28software%29







Developing C# on Linux

What is the file `packages/repositories.config`? Should it be kept under version control?

What is the Nuget repositories.config file for?

I have a test project in Visual Studio. I use *Microsoft.VisualStudio.TestTools.UnitTesting*.

I add this line in one of my unit tests:

    Console.WriteLine(&quot;Some foo was very angry with boo&quot;);
    Console.ReadLine();

When I run the test, the test passes, but the console window is not opened at all.

Is there a way to make the console window available to be interacted via a unit test?


Can I write into the console in a unit test? If yes, why doesn&#39;t the console window open?

How can I convert Persian date to Gregorian date using System.globalization.PersianCalendar?
Please note that I want to convert my Persian Date (e.g. today is 1391/04/07) and get the Gregorian Date result which will be 06/27/2012 in this case.
I&#39;m counting seconds for an answer ...

Convert Date from Persian to Gregorian

I&#39;m very new to ASP.NET 4.0 Web API. Can we redirect to another URL at the end of the POST action?, something like ... `Response.Redirect(url)`

Actually I upload file from a MVC application (say `www.abcmvc.com`) through Web API (say `www.abcwebapi.com/upload`) 

Here `upload` is the POST action. I post a multi-part form to Web API upload controller&#39;s post action. After uploading I would like to redirect back to `www.abcmvc.com`. 

Is this possible?



Redirect from asp.net web api post action

I am using .Net 3.5/4.0 with code in C#.

I am trying to get a version number of an exe file on my C: drive. 

For example path is: c:\Program\demo.exe. If the version number of demo.exe is 1.0.

How can i use this path to grab version number?. 



How to get .exe file version number from file path

I have a C lib and want to call function in this library from C# application. I tried creating a C++/CLI wrapper on the C lib by adding the C lib file as linker input and adding the source files as additional dependencies. 

Is there any better way to achieve this as am not sure how to add C output to c# application.

My C Code - 

    __declspec(dllexport) unsigned long ConnectSession(unsigned long handle,
    							unsigned char *	publicKey,
    							unsigned char	publicKeyLen);

My CPP Wrapper - 

    long MyClass::ConnectSessionWrapper(unsigned long handle,
        							unsigned char *	publicKey,
        							unsigned char	publicKeyLen)
    	{
    		return ConnectSession(handle, publicKey, publicKeyLen);
    	}



Is it possible to call a C function from C#.Net

I&#39;ve been having trouble using the `TransactionScope` to wrap multiple database queries into a transaction, I am using SqlBulkCopy with batchsize 500. When I increased the batch size to 1000 I am getting the error:

&gt; The transaction associated with the current connection has completed
&gt; but has not been disposed. The transaction must be disposed before the
&gt; connection can be used to execute SQL statements.

This is the code I am using:

    using (var scope = new TransactionScope())
	{
		using (var connection = (SqlConnection)customerTable.OpenConnection())
		{
			var table1BulkCopy = new SqlBulkCopy(connection)
			{
				BatchSize = BATCH_SIZE,
				DestinationTableName = TableName1
			};
		   
			table1BulkCopy.WriteToServer(table1DataTable);
		   
			var table2BulkCopy = new SqlBulkCopy(connection)
			{
				BatchSize = BATCH_SIZE,
				DestinationTableName = TableName2
			};
			
			table2BulkCopy.WriteToServer(table2DataTable);
						 
			var table3BulkCopy = new SqlBulkCopy(connection)
			{
				BatchSize = BATCH_SIZE,
				DestinationTableName = TableName3
			};
		   
			table1BulkCopy.WriteToServer(table3DataTable);
											
			var table4BulkCopy = new SqlBulkCopy(connection)
			{
				BatchSize = BATCH_SIZE,
				DestinationTableName = TableName4
			};
		   
			table4BulkCopy.WriteToServer(table4DataTable);
		   
			scope.Complete();
		}
	}

Error - The transaction associated with the current connection has completed but has not been disposed

At first I thought the code below works because if I have the group as &quot;IT&quot; it functions correctly because my username is in the IT group in active directory. What I learned is it always returns true whether I have my username in the IT group or not and if i change it to any other group I am in it returns always returns false. Any help would be appreciated.

        private void tabControl1_SelectedIndexChanged(object sender, EventArgs e)
        {
            // tab control security for admin tab
            bool admin = checkGroup(&quot;IT&quot;);

            if ((admin == true) &amp;&amp; (tabControl1.SelectedTab == tpHistory))
            {
                tabControl1.SelectedTab = tpHistory;
            }
            else if ((admin == false) &amp;&amp; (tabControl1.SelectedTab == tpHistory))
            {
                tabControl1.SelectedTab = tpRequests;
                MessageBox.Show(&quot;Unable to load tab. You have insufficient privileges.&quot;,
                    &quot;Access Denied&quot;, MessageBoxButtons.OK, MessageBoxIcon.Stop);
            }
        }

        // check active directory to see if user is in Marketing department group
        private static bool checkGroup(string group)
        {
            WindowsIdentity identity = WindowsIdentity.GetCurrent();
            WindowsPrincipal principal = new WindowsPrincipal(identity);
            return principal.IsInRole(group);
        }

How to check if a user belongs to an AD group?

I often find these terms being used in context of concurrent programming . Are they the same thing or different ?

Are &quot;data races&quot; and &quot;race condition&quot; actually the same thing in context of concurrent programming

I&#39;m building a queuing mechanism of sorts. There are rows of data that need processing, and a status flag. I&#39;m using an `update .. returning` clause to manage it:

    UPDATE stuff
    SET computed = &#39;working&#39;
    WHERE id = (SELECT id from STUFF WHERE computed IS NULL LIMIT 1)
    RETURNING * 

Is the nested select part the same lock as the update, or do I have a race condition here? If so, does the inner select need to be a `select for update`?

Atomic UPDATE .. SELECT in Postgres

I was reading the official Oracle documentation about Concurrency in Java and I was wondering what could be the difference between a `Collection` returned by

    public static &lt;T&gt; Collection&lt;T&gt; synchronizedCollection(Collection&lt;T&gt; c);

and using for example a 

`ConcurrentHashMap`. I&#39;m assuming that I use `synchronizedCollection(Collection&lt;T&gt; c)` on a `HashMap`. I know that in general a synchronized collection is essentially just a decorator for my `HashMap` so it is obvious that a `ConcurrentHashMap` has something different in its internals. Do you have some information about those implementation details?

**Edit: I realized that the source code is publicly available:**
[ConcurrentHashMap.java][1]


  [1]: http://www.docjar.com/html/api/java/util/concurrent/ConcurrentHashMap.java.html

How does ConcurrentHashMap work internally?

I&#39;m trying to understand what makes the lock in concurrency so important if one can use `synchronized (this)`. In the dummy code below, I can do either:

 1. synchronized the entire method or synchronize the vulnerable area (`synchronized(this){...}`)
 2. OR lock the vulnerable code area with a ReentrantLock.

Code:

        private final ReentrantLock lock = new ReentrantLock(); 
        private static List&lt;Integer&gt; ints;
	
        public Integer getResult(String name) { 
            .
            .
            .
            lock.lock();
            try {
                if (ints.size()==3) {
                    ints=null;
                    return -9;
                }	
			
                for (int x=0; x&lt;ints.size(); x++) {
                    System.out.println(&quot;[&quot;+name+&quot;] &quot;+x+&quot;/&quot;+ints.size()+&quot;. values &gt;&gt;&gt;&gt;&quot;+ints.get(x));
                }
			
            } finally {
                lock.unlock();
            } 
            return random;
    }

 

Why use a ReentrantLock if one can use synchronized(this)?

In [a version prior to the release of go 1.5 of the Tour of Go website][1], there&#39;s a piece of code that looks like this.

    package main
    
    import (
    	&quot;fmt&quot;
    	&quot;runtime&quot;
    )
    
    func say(s string) {
    	for i := 0; i &lt; 5; i++ {
    		runtime.Gosched()
    		fmt.Println(s)
    	}
    }
    
    func main() {
    	go say(&quot;world&quot;)
    	say(&quot;hello&quot;)
    }
The output looks like this:

    hello
    world
    hello
    world
    hello
    world
    hello
    world
    hello

What is bothering me is that when `runtime.Gosched()` is removed, the program no longer prints &quot;world&quot;.

    hello
    hello
    hello
    hello
    hello

Why is that so? How does `runtime.Gosched()` affect the execution?


  [1]: http://tour.golang.org/

What exactly does runtime.Gosched do?

I need to add http headers to the HttpClient before I send a request to a web service. How do I do that for an individual request (as opposed to on the HttpClient to all future requests)? I&#39;m not sure if this is even possible. 

	var client = new HttpClient();
	var task =
		client.GetAsync(&quot;http://www.someURI.com&quot;)
		.ContinueWith((taskwithmsg) =&gt;
		{
			var response = taskwithmsg.Result;

			var jsonTask = response.Content.ReadAsAsync&lt;JsonObject&gt;();
			jsonTask.Wait();
			var jsonObject = jsonTask.Result;
		});
	task.Wait();

Adding Http Headers to HttpClient

This occurred within the context of coding against Google Cloud Messaging, but applies elsewhere.

Consider the following:

    var http = new HttpClient();
    http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue(&quot;key=XXX&quot;);

and

    var http = new HttpClient();
    http.DefaultRequestHeaders.Add(&quot;Authorization&quot;, &quot;key=XXX&quot;);
    

both of which generate a FormatException:

&gt; System.FormatException : The format of value key=XXX&#39; is invalid.

The solution is to remove the equals sign.

1. Digging into reflector shows there is oodles of validation and parsing code that runs when adding a a new header value. Why is all this necessary? Shouldn&#39;t this client just be getting out of our way?

2. How do you escape the equals sign so that adding this value succeeds?


Adding HttpClient headers generates a FormatException with some values

I&#39;ve got the following code that works successfully.  I can&#39;t figure out how to get the cookie out of the response.  My goal is that I want to be able to set cookies in the request and get cookies out of the response.  Thoughts?

&lt;!-- language: lang-csharp --&gt;

    private async Task&lt;string&gt; Login(string username, string password)
    {
        try
        {
            string url = &quot;http://app.agelessemail.com/account/login/&quot;;
            Uri address = new Uri(url);
            var postData = new List&lt;KeyValuePair&lt;string, string&gt;&gt;
            {
                new KeyValuePair&lt;string, string&gt;(&quot;username&quot;, username),
                new KeyValuePair&lt;string, string&gt;(&quot;password &quot;, password)
            };

            HttpContent content = new FormUrlEncodedContent(postData);
            var cookieJar = new CookieContainer();
            var handler = new HttpClientHandler
            {
                CookieContainer = cookieJar,
                UseCookies = true,
                UseDefaultCredentials = false
            };

            var client = new HttpClient(handler)
            {
                BaseAddress = address
            };


            HttpResponseMessage response = await client.PostAsync(url,content);
            response.EnsureSuccessStatusCode();
            string body = await response.Content.ReadAsStringAsync();
            return body;
        }
        catch (Exception e)
        {
            return e.ToString();
        }
    }

Here is the complete answer:

&lt;!-- language: lang-csharp --&gt;

    HttpResponseMessage response = await client.PostAsync(url,content);
    response.EnsureSuccessStatusCode();

    Uri uri = new Uri(UrlBase);
    var responseCookies = cookieJar.GetCookies(uri);
    foreach (Cookie cookie in responseCookies)
    {
        string cookieName = cookie.Name;
        string cookieValue = cookie.Value;
    }


Struggling trying to get cookie out of response with HttpClient in .net 4.5

I am building a class library to interact with an API. I need to call the API and process the XML response. I can see the benefits of using `HttpClient` for Asynchronous connectivity, but what I am doing is purely synchronous, so I cannot see any significant benefit over using `HttpWebRequest`.

If anyone can shed any light I would greatly appreciate it. I am not one for using new technology for the sake of it.

Why use HttpClient for Synchronous Connection

I&#39;m writing an application that proxies some HTTP requests using the ASP.NET Web API and I am struggling to identify the source of an intermittent error.
It seems like a race condition... but I&#39;m not entirely sure.

Before I go into detail here is the general communication flow of the application:

 - **Client** makes a HTTP request to **Proxy 1**. 
 - **Proxy 1** relays the contents of the HTTP request to Proxy 2
 - **Proxy 2** relays the contents of the HTTP request to the Target Web Application
 - **Target Web App** responds to the HTTP request and the response is streamed (chunked transfer) to Proxy 2
 - **Proxy 2** returns the response to **Proxy 1** which in turn responds to the original calling **Client**.

The Proxy applications are written in ASP.NET Web API RTM using .NET 4.5.
The code to perform the relay looks like so:
&lt;!-- language: c# --&gt;

    //Controller entry point.
    public HttpResponseMessage Post()
    {
    	using (var client = new HttpClient())
    	{
    		var request = BuildRelayHttpRequest(this.Request);
    		
    		//HttpCompletionOption.ResponseHeadersRead - so that I can start streaming the response as soon
    		//As it begins to filter in.
    		var relayResult = client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead).Result;
    		
    		var returnMessage = BuildResponse(relayResult);
    		return returnMessage;
    	}
    }
    
    private static HttpRequestMessage BuildRelayHttpRequest(HttpRequestMessage incomingRequest)
    {
    	var requestUri = BuildRequestUri();
    	var relayRequest = new HttpRequestMessage(incomingRequest.Method, requestUri);
    	if (incomingRequest.Method != HttpMethod.Get &amp;&amp; incomingRequest.Content != null)
    	{
           relayRequest.Content = incomingRequest.Content;
    	}
    	
    	//Copies all safe HTTP headers (mainly content) to the relay request
    	CopyHeaders(relayRequest, incomingRequest);
    	return relayRequest;
    }
    
    private static HttpRequestMessage BuildResponse(HttpResponseMessage responseMessage)
    {
    	var returnMessage = Request.CreateResponse(responseMessage.StatusCode);
    	returnMessage.ReasonPhrase = responseMessage.ReasonPhrase;
    	returnMessage.Content = CopyContentStream(responseMessage);
    	
    	//Copies all safe HTTP headers (mainly content) to the response
    	CopyHeaders(returnMessage, responseMessage);
    }
    
    private static PushStreamContent CopyContentStream(HttpResponseMessage sourceContent)
    {
    	var content = new PushStreamContent(async (stream, context, transport) =&gt;
    			await sourceContent.Content.ReadAsStreamAsync()
    							.ContinueWith(t1 =&gt; t1.Result.CopyToAsync(stream)
    								.ContinueWith(t2 =&gt; stream.Dispose())));
    	return content;
    }
The error that occurs intermittently is:

&gt; An asynchronous module or handler completed while an asynchronous operation was still pending.

This error usually occurs on the first few requests to the proxy applications after which the error is not seen again.

Visual Studio never catches the Exception when thrown.
But the error can be caught in the Global.asax Application_Error event.
Unfortunately the Exception has no Stack Trace.

The proxy applications are hosted in Azure Web Roles.

Any help identifying the culprit would be appreciated.

Content Type	Original Author	Original Content on Stackoverflow
Question	Alex K	View Question on Stackoverflow
Solution 1 - .Net	Marcel N.	View Answer on Stackoverflow
Solution 2 - .Net	muruge	View Answer on Stackoverflow
Solution 3 - .Net	Alex K	View Answer on Stackoverflow

Is HttpClient safe to use concurrently?

.Net Problem Overview

.Net Solutions

Solution 1 - .Net

Solution 2 - .Net

Solution 3 - .Net

How to replace an entire line in a text file by line number

Measure the time it takes to execute a t-sql query

Attributions