You can use:

    File.WriteAllBytes(&quot;Foo.txt&quot;, arrBytes); // Requires System.IO

If you have an enumerable and not an array, you can use:

    File.WriteAllBytes(&quot;Foo.txt&quot;, arrBytes.ToArray()); // Requires System.Linq



You can use [File.WriteAllBytes][1]


  [1]: http://msdn.microsoft.com/en-us/library/system.io.file.writeallbytes.aspx

So I have this class:

    public class Foo&lt;T&gt; where T : ???
    {
        private T item;

        public bool IsNull()
        {
            return item == null;
        }

    }

Now I am looking for a type constraint that allows me to use everything as type parameter that can be `null`. That means all reference types, as well as all the `Nullable` (`T?`) types:

    Foo&lt;String&gt; ... = ...
    Foo&lt;int?&gt; ... = ...

should be possible.

Using `class` as the type constraint only allows me to use the reference types.

*Additional Information:*
I am writing a pipes and filters application, and want to use a `null` reference as the last item that passes into the pipeline, so that every filter can shut down nicely, do cleanup, etc...
 


C# generic type constraint for everything nullable

I am trying to understand what is machine epsilon. According to the Wikipedia, it can be calculated as follows:

    def machineEpsilon(func=float):
        machine_epsilon = func(1)
        while func(1)+func(machine_epsilon) != func(1):
            machine_epsilon_last = machine_epsilon
            machine_epsilon = func(machine_epsilon) / func(2)
        return machine_epsilon_last

However, it is suitable only for double precision numbers. I am interested in modifying it to support also single precision numbers. I read that numpy can be used, particularly `numpy.float32` class. Can anybody help with modifying the function? 

python numpy machine epsilon

I have a byte array (an IEnumerable&lt;byte&gt; actually), and I need to save it to a new file containing this data.

How do I do that?

I found some answers telling how to create a MemoryStream from that, but still can&#39;t save it to a brand new file.

Save byte array to file

I have a byte array (an IEnumerable<byte> actually), and I need to save it to a new file containing this data.</byte>
How do I do that?
I found some answers telling how to create a MemoryStream from that, but still can't save it to a brand new file.

using: MVC 4, ASP.NET Razor

I&#39;m getting an error that looks like it shouldn&#39;t be possible. It tells me that i&#39;m using a null-reference, States, but clearly it is being set. 



Controller:

    public ActionResult Index()
    {
        Dictionary&lt;int, string&gt; states = new Dictionary&lt;int, string&gt;()
        {
            { -1, &quot;a&quot;},
            { 0, &quot;b&quot;},
            { 1, &quot;c&quot;},
            { 2, &quot;d&quot;},
        };

        //assigning states
        ViewBag.States = states;

        foreach (KeyValuePair&lt;int, string&gt; de in ViewBag.States)
        {
            Debug.WriteLine(de.Key);
        }
        return View();
    }


The View: 

    &lt;div class=&quot;search-input&quot;&gt;
        &lt;select&gt;
            @foreach (KeyValuePair&lt;int, string&gt; de in ViewBag.States)
            {
                &lt;option value=&quot;@de.Key&quot;&gt;@de.Value&lt;/option&gt;
            }
        &lt;/select&gt;
    &lt;/div&gt;

The error: 

    Cannot perform runtime binding on a null reference
    Line 54: @foreach (KeyValuePair&lt;int, string&gt; de in ViewBag.States)



Cannot perform runtime binding on a null reference, But it is NOT a null reference

I am using the release version (RTM, not RC) of Visual Studio 2013 (downloaded from MSDN 2013-10-18) and therefore the latest (RTM) version of AspNet.Identity. When I create a new web project, I select &quot;Individual User Accounts&quot; for authentication. This creates the following tables:

1. AspNetRoles
2. AspNetUserClaims
3. AspNetUserLogins
4. AspNetUserRoles
5. AspNetUsers

When I register a new user (using the default template), these tables (listed above) are created and the AspNetUsers table has a record inserted which contains:

1. Id
2. UserName
3. PasswordHash
4. SecurityStamp
5. Discriminator

Additionally, by adding public properties to the class &quot;ApplicationUser&quot; I have successfully added additional fields to the AspNetUsers table, such as &quot;FirstName&quot;, &quot;LastName&quot;, &quot;PhoneNumber&quot;, etc.

Here&#39;s my question. Is there a way to change the names of the above tables (when they are first created) or will they always be named with the `AspNet` prefix as I listed above? If the table names can be named differently, please explain how.

**-- UPDATE --**

I implemented @Hao Kung&#39;s solution. It does create a new table (for example I called it MyUsers), but it also still creates the AspNetUsers table. The goal is to replace the &quot;AspNetUsers&quot; table with the &quot;MyUsers&quot; table. See code below and database image of tables created.

I would actually like to replace each `AspNet` table with my own name... For fxample, MyRoles, MyUserClaims, MyUserLogins, MyUserRoles, and MyUsers.

How do I accomplish this and end up with only one set of tables?

    public class ApplicationUser : IdentityUser
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Address1 { get; set; }
        public string Address2 { get; set; }
        public string City { get; set; }
        public string State { get; set; }
        public string PostalCode { get; set; }
        public string PhonePrimary { get; set; }
        public string PhoneSecondary { get; set; }
    }

    public class ApplicationDbContext : IdentityDbContext&lt;ApplicationUser&gt;
    {
        public ApplicationDbContext(): base(&quot;DefaultConnection&quot;)
        {
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity&lt;IdentityUser&gt;().ToTable(&quot;MyUsers&quot;);
        }
    }

![Database Tables][1]

  [1]: http://i.stack.imgur.com/P1p5S.png

**-- UPDATE ANSWER --**

Thanks to both Hao Kung and Peter Stulinski. This solved my problem...

        protected override void OnModelCreating(System.Data.Entity.DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity&lt;IdentityUser&gt;().ToTable(&quot;MyUsers&quot;).Property(p =&gt; p.Id).HasColumnName(&quot;UserId&quot;);
            modelBuilder.Entity&lt;ApplicationUser&gt;().ToTable(&quot;MyUsers&quot;).Property(p =&gt; p.Id).HasColumnName(&quot;UserId&quot;);
            modelBuilder.Entity&lt;IdentityUserRole&gt;().ToTable(&quot;MyUserRoles&quot;);
            modelBuilder.Entity&lt;IdentityUserLogin&gt;().ToTable(&quot;MyUserLogins&quot;);
            modelBuilder.Entity&lt;IdentityUserClaim&gt;().ToTable(&quot;MyUserClaims&quot;);
            modelBuilder.Entity&lt;IdentityRole&gt;().ToTable(&quot;MyRoles&quot;);
        }


How can I change the table names when using ASP.NET Identity?

I have a strange error. I&#39;m experimenting with a .NET 4.5 Web API, Entity Framework and MS SQL Server. I&#39;ve already created the database and set up the correct primary and foreign keys and relationships.

I&#39;ve created a .edmx model and imported two tables: Employee and Department. A department can have many employees and this relationship exists. I created a new controller called EmployeeController using the scaffolding options to create an API controller with read/write actions using Entity Framework. In the wizard, selected Employee as the model and the correct entity for the data context.

The method that is created looks like this:

    public IEnumerable&lt;Employee&gt; GetEmployees()
    {
        var employees = db.Employees.Include(e =&gt; e.Department);
        return employees.AsEnumerable();
    }

When I call my API via /api/Employee, I get this error:

&gt;The &#39;ObjectContent`1&#39; type failed to serialize the response body for content type &#39;application/json; ...System.InvalidOperationException&quot;,&quot;StackTrace&quot;:null,&quot;InnerException&quot;:{&quot;Message&quot;:&quot;An error has occurred.&quot;,&quot;ExceptionMessage&quot;:&quot;Self referencing loop detected with type &#39;System.Data.Entity.DynamicProxies.Employee_5D80AD978BC68A1D8BD675852F94E8B550F4CB150ADB8649E8998B7F95422552&#39;. Path &#39;[0].Department.Employees&#39;.&quot;,&quot;ExceptionType&quot;:&quot;Newtonsoft.Json.JsonSerializationException&quot;,&quot;StackTrace&quot;:&quot;   ...

Why is it self referencing [0].Department.Employees? That doesn&#39;t make a whole lot of sense. I would expect this to happen if I had circular referencing in my database but this is a very simple example. What could be going wrong?

Entity framework self referencing loop detected

I have a solution with 3 projects:

 - ParsersBase, that define an interface IParseRule
 - ParsersLibrary, that have a reference to ParsersBase and define a class HtmlImageUrlParseRule : IParseRule
 - ParsersLibraryTest, that have a reference to ParsersBase and ParsersLibrary and define a test class with some test methods

When I&#39;m trying to build it, I get a warning:

&gt; Reference to type &#39;AVSoft.ParsersBase.IParseRule&#39; claims it is defined in &#39;c:\Users\Tim\Dropbox\projects\Image Downloader\ParsersLibrary\bin\Debug\ParsersLibrary.dll&#39;, but it could not be found

Why VS is trying to find `AVSoft.ParsersBase.IParseRule` in ParsersLibrary.dll? ParsersLibraryTest has a reference to ParsersBase, it just doesn&#39;t make any sense.

Error: Reference to type claims it is defined, but it could not be found

I was going through a action method code and i saw one attribute was used there but i really did not understand the use. here is the code

    public ActionResult User([Bind(Include = &quot;Username,FullName,Email&quot;)]User user)
    {
       if (!ModelState.IsValid()) return View(user);
    
       try
       {
         user.save()
         // return the view again or redirect the user to another page
       }
       catch(Exception e)
       {
         ViewData[&quot;Message&quot;] = e.Message;
         return View(user)
       }
    }

    ([Bind(Include = &quot;Username,FullName,Email&quot;)]User user)
i just do not understand the above line Bind include etc

so please help me to understand this kind of attribute used &amp; when people write this kind of code in mvc. it will be really good help if some one make me understand with sample small code where they will use this `Bind attribute`.

**Update:**
Suppose i have form from where user can enter only FirstName,LastName &amp; Gender then my action method looks like 

    public ActionResult Edit(string FirstName,string LastName,string Gender)
    {
        // ...
    }

this will work i think. then why i should use a Bind Attribute because my above action method will works fine.

Need guide line for MVC action method with Bind attribute

I installed Logstash to parse apache files. It took me quite q while to get the settings right and I always tried on real logs. I noticed (as the documentation says) that logstash &quot;remembers&quot; where it was in a file. Now my setings are Ok and I would like Logstash to &quot;forget&quot;. This seems harder than I though. I already did the following:

 - used: `start_position =&gt; &quot;beginning&quot;`

 - deleted the complete &quot;data&quot; folder from elastissearch (and stopped it first)

 - looked at which files where opened by logstash with `lsof -p PID` and deleted everything which was promising (in my case `/tmp/jffi*.tmp`)

Still Logstash does not forget and parse only &quot;fresh&quot; files in the folder where the logs are

Any ideas?

How to force Logstash to reparse a file?

I&#39;m new to Python and I&#39;ve been going through the Q&amp;A on this site, for an answer to my question. However, I&#39;m a beginner and I find it difficult to understand some of the solutions. I need a very basic solution.

Could someone please explain a simple solution to &#39;Downloading a file through http&#39; and &#39;Saving it to disk, in Windows&#39;, to me?

I&#39;m not sure how to use shutil and os modules, either.

The file I want to download is under 500 MB and is an .gz archive file.If someone can explain how to extract the archive and utilise the files in it also, that would be great!

Here&#39;s a partial solution, that I wrote from various answers combined:

    import requests
    import os
    import shutil

    global dump

    def download_file():
        global dump
        url = &quot;http://randomsite.com/file.gz&quot;
        file = requests.get(url, stream=True)
        dump = file.raw

    def save_file():
        global dump
        location = os.path.abspath(&quot;D:\folder\file.gz&quot;)
        with open(&quot;file.gz&quot;, &#39;wb&#39;) as location:
            shutil.copyfileobj(dump, location)
        del dump

Could someone point out errors (beginner level) and explain any easier methods to do this?

Thanks!

Basic http file downloading and saving to disk in python?

I need to make a script that can write one line of text to a text file in the same directory as the batch file.

How can I use a batch file to write to a text file?

I have some classes that implements some logic related to file system and files. For example, I am performing following tasks as part of this logic:

- checking if certain folder has certain structure (eg. it contains subfolders with specific names etc...)
- loading some files from those folders and checking their structure (eg. these are some configuration files, located at certain place within certain folder)
- load additional files for testing/validation from the configuration file (eg. this config file contains information about other files in the same folder, that should have other internal structure etc...)

Now all this logic has some workflow and exceptions are thrown, if something is not right (eg. configuration file is not found at the specific folder location). In addition, there is [Managed Extensibility Framework (MEF)][1] involved in this logic, because some of these files I am checking are managed DLLs that I am manually loading to MEF aggregates etc...

Now I&#39;d like to test all this in some way. I was thinking of creating several physical test folders on HDD, that cover various test cases and then run my code against them. I could create for example:

- folder with correct structure and all files being valid
- folder with correct structure but with invalid configuration file
- folder with correct structure but missing configuration file
etc...

Would this be the right approach? I am not sure though how exactly to run my code in this scenario... I certainly don&#39;t want to run the whole application and point it to check these mocked folders. Should I use some unit testing framework to write kind of &quot;unit tests&quot;, that executes my code against these file system objects? 

In general, is all this a correct approach for this kind of testing scenarios? Are there other better approaches?


  [1]: http://msdn.microsoft.com/en-us/library/dd460648%28v=vs.110%29.aspx

How to do integration testing in .NET with real files?

I want to create a new file in dired mode. Is there &quot;create new file&quot; command in dired mode ?  For example, When I type &quot;c&quot; in dired mode, it creates &quot;untitled.txt&quot;. It&#39;s very simple , but I can&#39;t find it.

How to create new file from dired mode?

I need to run two commands in series that need to read data from the same stream.
After piping a stream into another the buffer is emptied so i can&#39;t read data from that stream again so this doesn&#39;t work:


    var spawn = require(&#39;child_process&#39;).spawn;
    var fs = require(&#39;fs&#39;);
    var request = require(&#39;request&#39;);

    var inputStream = request(&#39;http://placehold.it/640x360&#39;);
    var identify = spawn(&#39;identify&#39;,[&#39;-&#39;]);

    inputStream.pipe(identify.stdin);

    var chunks = [];
    identify.stdout.on(&#39;data&#39;,function(chunk) {
      chunks.push(chunk);
    });

    identify.stdout.on(&#39;end&#39;,function() {
      var size = getSize(Buffer.concat(chunks)); //width
      var convert = spawn(&#39;convert&#39;,[&#39;-&#39;,&#39;-scale&#39;,size * 0.5,&#39;png:-&#39;]);
      inputStream.pipe(convert.stdin);
      convert.stdout.pipe(fs.createWriteStream(&#39;half.png&#39;));
    });

    function getSize(buffer){
      return parseInt(buffer.toString().split(&#39; &#39;)[2].split(&#39;x&#39;)[0]);
    }

**Request** complains about this

    Error: You cannot pipe after data has been emitted from the response.

and changing the **inputStream** to `fs.createWriteStream` yields the same issue of course.
I don&#39;t want to write into a file but _reuse_ in some way the stream that **request** produces (or any other for that matter).


Is there a way to reuse a readable stream once it finishes piping?
What would be the best way to accomplish something like the above example?




Node.js Piping the same readable stream into multiple (writable) targets

I have a relatively small file (some hundreds of kilobytes) that I want to be in memory for direct access for the entire execution of the code.

I don&#39;t know exactly the internals of Node.js, so I&#39;m asking if a `fs open` is enough or I have to read all file and copy to a `Buffer`? 



Buffer entire file in memory with Node.js

In all examples that use some kind of buffering I see they use stream instead of string. How is std::ostringstream and &lt;&lt; operator different than using string.append. Which one is faster and which one uses less resourses (memory).

One difference I know is that you can output different types into output stream (like integer) rather than the limited types that string::append accepts.

Here is an example:

    std::ostringstream os;
    os &lt;&lt; &quot;Content-Type: &quot; &lt;&lt; contentType &lt;&lt; &quot;;charset=&quot; &lt;&lt; charset &lt;&lt; &quot;\r\n&quot;;
    std::string header = os.str();

vs

    std::string header(&quot;Content-Type: &quot;);
    header.append(contentType);
    header.append(&quot;;charset=&quot;);
    header.append(charset);
    header.append(&quot;\r\n&quot;);

Obviously using stream is shorter, but I think append returns reference to the string so it can be written like this:

    std::string header(&quot;Content-Type: &quot;);
    header.append(contentType)
      .append(&quot;;charset=&quot;)
      .append(charset)
      .append(&quot;\r\n&quot;);

And with output stream you can do:

    std::string content;
    ...
    os &lt;&lt; &quot;Content-Length: &quot; &lt;&lt; content.length() &lt;&lt; &quot;\r\n&quot;;

But what about memory usage and speed? Especially when used in a big loop.

**Update:**

To be more clear the question is: **Which one should I use and why? Is there situations when one is preferred or the other?** For performance and memory ... well I think benchmark is the only way since every implementation could be different.

**Update 2:**

Well I don&#39;t get clear idea what should I use from the answers which means that any of them will do the job, plus vector.  `Cubbi` did nice benchmark with the addition of Dietmar K&#252;hl that the biggest difference is construction of those objects. If you are looking for an answer you should check that too. I&#39;ll wait a bit more for other answers (look previous update) and if I don&#39;t get one I think I&#39;ll accept Tolga&#39;s answer because his suggestion  to use vector is already done before which means vector should be less resource hungry.


c++ std::ostringstream vs std::string::append

I&#39;ve often heard of Streams2 and old-streams, but what is Streams3? [It get mentioned in this talk by Thorsten Lorenz](http://youtu.be/9llfAByho98?t=45s).

Where can I read about it, and what is the difference between Streams2 and Streams3.

Doing a search on Google, I also see it mentioned in the [Changelog of Node 0.11.5](http://blog.nodejs.org/2013/08/06/node-v0-11-5-unstable/),

&gt; stream: Simplify flowing, passive data listening (streams3) (isaacs)


What is Streams3 in Node.js and how does it differ from Streams2?

What&#39;s the correct way to handle errors with streams? I already know there&#39;s an &#39;error&#39; event you can listen on, but I want to know some more details about arbitrarily complicated situations. 

For starters, what do you do when you want to do a simple pipe chain:

`input.pipe(transformA).pipe(transformB).pipe(transformC)...`

And how do you properly create one of those transforms so that errors are handled correctly? 

More related questions:

 * when an error happens, what happens to the &#39;end&#39; event? Does it never get fired? Does it sometimes get fired? Does it depend on the transform/stream? What are the standards here?
 * are there any mechanisms for propogating errors through the pipes? 
 * do domains solve this problem effectively? Examples would be nice.
 * do errors that come out of &#39;error&#39; events have stack traces? Sometimes? Never? is there a way to get one from them?

Error handling with node.js streams

What is the difference between: 

    npm install [package_name]

and: 

    npm install [package_name] --save

and:

    npm install [package_name] --save-dev

What does this mean? And what is really the effect of `--save` and `-dev` keywords?

What is the difference between --save and --save-dev?

Is it possible to save a numpy array appending it to an already existing npy-file --- something like `np.save(filename,arr,mode=&#39;a&#39;)`?

I have several functions that have to iterate over the rows of a large array. I cannot create the array at once because of memory constrains. To avoid to create the rows over and over again, I wanted to create each row once and save it to file appending it to the previous row in the file. Later I could load the npy-file in mmap_mode, accessing the slices when needed.

save numpy array in append mode

I use `Sublime text`. Now I am trying `Atom`. When I save any file in sublime text it does not include any trailing blank line. But saving any file in `Atom` leaves a trailing blank line. How do I force `Atom` not to leave trailing white spaces?

Atom text editor remove trailing whitespace on save

I need to generate a function to call after or before save() or update() but i don&#39;t know how to do.
I think I need a callback from save() update() but I don&#39;t know how to do.
Thanks

Laravel: how to create a function After or Before save|update

Adding the prefix &quot;b&quot; to a string converts it to bytes:

    b&#39;example&#39;

But I can&#39;t figure out how to do this with a variable. Assuming `string = &#39;example&#39;`, none of these seem to work:

    b(string)
    b string
    b&#39;&#39; + string

Is there a simple way to do this?

Add &quot;b&quot; prefix to python variable?

Until now I believed that 1024 bytes equals 1 KB (kilobyte) but I was reading on the internet about decimal and binary system.

![enter image description here][1]


  [1]: http://i.stack.imgur.com/sR9WU.png

So, actually 1024 bytes = 1 KB would be the correct way to define or simply there is a general confusion?

Really 1 KB (KiloByte) equals 1024 bytes?

    1 byte = 8 bits 

So, does this mean 1 byte can only hold one character? E.g.:

    &quot;16&quot; uses 2 bytes , &quot;9&quot; uses 1 byte , &quot;a&quot; uses 1 byte, &quot;b&quot; uses 1 byte 

and if `tiny int` has range of 0-255, does this mean it can be stored with 255 char?

what is storage of 

    1. tiny int (1)
    2. tiny int (2) 

what will be the `range 0-10` 

How many characters can you store with 1 byte?

I wanted to try out the python BytesIO class.

As an experiment I tried writing to a zip file in memory, and then reading the bytes back out of that zip file. So instead of passing in a file-object to `gzip`, I pass in a `BytesIO` object. Here is the entire script:

    from io import BytesIO
    import gzip

    # write bytes to zip file in memory
    myio = BytesIO()
    with gzip.GzipFile(fileobj=myio, mode=&#39;wb&#39;) as g:
        g.write(b&quot;does it work&quot;)
    
    # read bytes from zip file in memory
    with gzip.GzipFile(fileobj=myio, mode=&#39;rb&#39;) as g:
        result = g.read()

    print(result)

But it is returning an empty `bytes` object for `result`. This happens in both Python 2.7 and 3.4. What am I missing?


Writing then reading in-memory bytes (BytesIO) gives a blank result

Java 8 provides `Stream&lt;T&gt;` specializations for `double`, `int` and `long`: `DoubleStream`, `IntStream` and `LongStream` respectively.  However, I could not find an equivalent for `byte` in [the documentation][1]. 

Does Java 8 provide a `ByteStream` class? 


  [1]: https://docs.oracle.com/javase/8/docs/api/java/util/stream/BaseStream.html

Content Type	Original Author	Original Content on Stackoverflow
Question	Daniel Möller	View Question on Stackoverflow
Solution 1 - C#	Mike Christensen	View Answer on Stackoverflow
Solution 2 - C#	Anirudha	View Answer on Stackoverflow

Save byte array to file

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

python numpy machine epsilon

C# generic type constraint for everything nullable

Attributions