Because [`Convert.ToInt32`][1] rounds:

&gt; Return Value: rounded to the nearest 32-bit signed integer. If value
&gt; is halfway between two whole numbers, the even number is returned;
&gt; that is, 4.5 is converted to 4, and 5.5 is converted to 6.

...while the cast [truncates][2]:

&gt; When you convert from a double or float value to an integral type, the
&gt; value is truncated.

**Update:** See Jeppe Stig Nielsen&#39;s comment below for additional differences (which however do not come into play if `score` is a real number as is the case here).

  [1]: http://msdn.microsoft.com/en-us/library/ffdk7eyz.aspx
  [2]: http://msdn.microsoft.com/en-us/library/yht2cx7b.aspx

Casting will ignore anything after the decimal point, so 8.6 becomes 8.

`Convert.ToInt32(8.6)` is the safe way to ensure your double gets rounded to the nearest integer, in this case 9.

you can round your double and cast ist:

    (int)Math.Round(myDouble);

In the provided example your decimal is **8.6**. Had it been 8.5 or 9.5, the statement **i1 == i2**  might have been true. Infact it would have been true for 8.5, and false for 9.5. 

**Explanation:** 

Regardless of the decimal part, the second statement, `int i2 = (int)score` will discard the decimal part and simply return you the integer part. Quite dangerous thing to do, as data loss might occur.

Now, for the first statement, two things can happen. If the decimal part is 5, that is, it is half way through, a decision is to be made. Do we round up or down? In C#, the Convert class implements banker&#39;s rounding. See [this][1] answer for deeper explanation. Simply put, if the number is even, round down, if the number is odd, round up.


E.g. Consider:

            double score = 8.5;
            int i1 = Convert.ToInt32(score); // 8
            int i2 = (int)score;             // 8

            score += 1;
            i1 = Convert.ToInt32(score);     // 10
            i2 = (int)score;                 // 9


  [1]: https://stackoverflow.com/questions/311696/why-does-net-use-bankers-rounding-as-default

ToInt32 rounds.  Casting to int just throws away the non-integer component.

I&#39;m very new to HTML/CSS and I&#39;m trying to display some text as like 50% transparent.  So far I have the HTML to display the text with full opacity

    &lt;html&gt;&lt;font color=\&quot;black\&quot; face=\&quot;arial\&quot; size=\&quot;4\&quot;&gt;THIS IS MY TEXT&lt;/font&gt;&lt;/html&gt;

However, I&#39;m not sure how to change its opacity. I&#39;ve tried looking online, but I&#39;m not sure exactly what to do with the code I find.

How to change text transparency in HTML/CSS?

Is there a way in Handlebars.js templating to check if the collection or list is null or empty, before going and iterating through the list/collection?

    // if list is empty do some rendering ... otherwise do the normal
    {{#list items}}
    
    {{/list}}



    {{#each items}}
    
    {{/each}}

handlerbars.js check if list is empty

In our code we have a double that we need to convert to an int.

    double score = 8.6;
    int i1 = Convert.ToInt32(score);
    int i2 = (int)score;

Can anyone explain me why `i1 != i2`?

The result that I get is that: `i1 = 9` and `i2 = 8`.

Converting a double to an int in C#

In our code we have a double that we need to convert to an int.
<pre><code class="hljs language-ini">double score = 8.6;
int i1 = Convert.ToInt32(score);
int i2 = (int)score;
</code></pre>
Can anyone explain me why <code>i1 != i2</code>?
The result that I get is that: <code>i1 = 9</code> and <code>i2 = 8</code>.

I&#39;m not able to access values in configuration file.

    Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
    var clientsFilePath = config.AppSettings.Settings[&quot;ClientsFilePath&quot;].Value; 
    // the second line gets a NullReferenceException

**.config file**:

&lt;!-- language: lang-xml --&gt;

    &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot; ?&gt;
    &lt;configuration&gt;
      &lt;appSettings&gt;
        &lt;!-- ... --&gt;
        &lt;add key=&quot;ClientsFilePath&quot; value=&quot;filepath&quot;/&gt;
        &lt;!-- ... --&gt;
      &lt;/appSettings&gt;
    &lt;/configuration&gt;

Do you have any suggestion what should I do?

AppSettings get value from .config file

I want to send temperature value from a microcontroller using UART to C# interface and Display temperature on `Label.Content`. Here is my microcontroller code:

    while(1) {
       key_scan(); // get value of temp
       if (Usart_Data_Ready())
       {
          while(temperature[i]!=0)
          {
             if(temperature[i]!=&#39; &#39;)
             {
                Usart_Write(temperature[i]);
                Delay_ms(1000);
             }
             i = i + 1;
          }
          i =0;
          Delay_ms(2000);
       }
    }

and my C# code is:

    private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
    {
       txt += serialPort1.ReadExisting().ToString();
       textBox1.Text = txt.ToString();
    }


but exception arises there &quot;**Cross-thread operation not valid: Control &#39;textBox1&#39; accessed from a thread other than the thread it was created on**&quot;
Please tell me how to get temperature string from my microcontroller and remove this Error!

Cross-thread operation not valid: Control &#39;textBox1&#39; accessed from a thread other than the thread it was created on

I want to make a MessageBox confirmation. Here is the message box:

    MessageBox.Show(&quot;Do you want to save changes?&quot;, &quot;Confirmation&quot;, messageBoxButtons.YesNoCancel);

And I want to make something like this (in pseudocode):

    if (MessageBox.Result == DialogResult.Yes)
        ;
    else if (MessageBox.Result == DialogResult.No)
        ;
    else
        ;

How can I do that in C#?


C# MessageBox dialog result

Like the title suggests, is there an equivalent to `Process.Start` (allows you run another application or batch file) that I can await?

I&#39;m playing with a small console app and this seemed like the perfect place to be using async and await but I can&#39;t find any documentation for this scenario.

What I&#39;m thinking is something along these lines:

    void async RunCommand()
    {
        var result = await Process.RunAsync(&quot;command to run&quot;);
    }

Is there any async equivalent of Process.Start?

I have searched about static variables in C#, but I am still not getting what its use is. Also, if I try to declare the variable inside the method it will not give me the permission to do this. Why?

   I have seen some examples about the static variables. I&#39;ve seen that we don&#39;t need to create an instance of the class to access the variable, but that is not enough to understand what its use is and when to use it.

**Second thing**

    class Book
    {
        public static int myInt = 0;
    }

    public class Exercise
    {
        static void Main()
        {
            Book book = new Book();

            Console.WriteLine(book.myInt); // Shows error. Why does it show me error?
                                           // Can&#39;t I access the static variable 
                                           // by making the instance of a class?

            Console.ReadKey();
        }
    }

What is the use of static variable in C#? When to use it? Why can&#39;t I declare the static variable inside method?

Why does the first and second Write work but not the last? Is there a way I can allow all 3 of them and detect if it was 1, (int)1 or i passed in? And really why is one allowed but the last? The second being allowed but not the last really blows my mind.

[Demo to show compile error](http://ideone.com/tQjCm)

	using System;
	class Program
	{
		public static void Write(short v) { }
		static void Main(string[] args)
		{
			Write(1);//ok
			Write((int)1);//ok
			int i=1;
			Write(i);//error!?
		}
	}




Why can I pass 1 as a short, but not the int variable i?

Does an Integer variable in C occupy 2 bytes or 4 bytes? What are the factors that it depends on?

Most of the textbooks say integer variables occupy 2 bytes.
But when I run a program printing the successive addresses of an array of integers it shows the difference of 4.

Is the size of C &quot;int&quot; 2 bytes or 4 bytes?

`selectedItem` has two fields:

* `int? _cost`
* `string _serialNumber`

In this example, `_cost` and `_serialNumber` of `selectedItem` are BOTH null. I am reading through the fields of `selectedItem` via their properties, and filling in textboxes with their values, when...

    TextBox1.Text = selectedItem.Cost.ToString(); //no error
    TextBox2.Text = selectedItem.SerialNumber.ToString(); //error

I understand that `SerialNumber.ToString()` is redundant (because it is already a string), but I don&#39;t understand why this causes this exception:
&gt; Nullable object must have a value.

* `int? _cost` is nullable, and does not have a value, yet it does not give me the exception.
* `string _serialNumber` is nullable, and does not have a value, yet it **does** give me the exception.

This [question][1] touches on it, the guy is essentially asking the same thing, but there is no designated answer, and it also doesn&#39;t explain why a nullable `int`? For example, can I use `.ToString()` on a nullable int but not on a null string?

  [1]: https://stackoverflow.com/questions/4793601/tostring-on-null-string

Why does .ToString() on a null string cause a null error, when .ToString() works fine on a nullable int with null value?

Is there a preferred way to keep the data type of a `numpy` array fixed as `int` (or `int64` or whatever), while still having an element inside listed as `numpy.NaN`?

In particular, I am converting an in-house data structure to a Pandas DataFrame. In our structure, we have integer-type columns that still have NaN&#39;s (but the dtype of the column is int). It seems to recast everything as a float if we make this a DataFrame, but we&#39;d really like to be `int`.

Thoughts?

**Things tried:**

I tried using the `from_records()` function under pandas.DataFrame, with `coerce_float=False` and this did not help. I also tried using NumPy masked arrays, with NaN fill_value, which also did not work. All of these caused the column data type to become a float.

NumPy or Pandas: Keeping array type as integer while having a NaN value

Basically my mate has been saying that I could make my code shorter by using a different way of checking if an int array contains an int, although he won&#39;t tell me what it is :P.

Current: 

    public boolean contains(final int[] array, final int key) {
        for (final int i : array) {
            if (i == key) {
                return true;
            }
        }
        return false;
    }

Have also tried this, although it always returns false for some reason.

    public boolean contains(final int[] array, final int key) {
        return Arrays.asList(array).contains(key);
    }

Could anyone help me out?

Thank you.

Java, Simplified check if int array contains int

Is there a function that can truncate or round a Double?  At one point in my code I would like a number like: `1.23456789` to be rounded to `1.23`

Scala Doubles, and Precision

I have a long string with double-type values separated by `#` -`value1#value2#value3#` etc

I splitted it to string table. Then, I want to convert every single element from this table to double type and I get an error. What is wrong with type-conversion here?

    string a = &quot;52.8725945#18.69872650000002#50.9028073#14.971600200000012#51.260062#15.5859949000000662452.23862099999999#19.372202799999250800000045#51.7808372#19.474096499999973#&quot;;
    string[] someArray = a.Split(new char[] { &#39;#&#39; });
    for (int i = 0; i &lt; someArray.Length; i++)
    {
		Console.WriteLine(someArray[i]); // correct value
		Convert.ToDouble(someArray[i]); // error
    }


Converting string to double in C#

I have a large amount of numeric values `y` in javascript.  I want to group them by rounding them down to the nearest multiple of `x` and convert the result to a string. 

How do I get around the annoying floating point precision?  

For example:

    0.2 + 0.4 = 0.6000000000000001

Two things I have tried:

    &gt;&gt;&gt; y = 1.23456789 
    &gt;&gt;&gt; x = 0.2 
    &gt;&gt;&gt; parseInt(Math.round(Math.floor(y/x))) * x; 
    1.2000000000000002

and:

    &gt;&gt;&gt; y = 1.23456789 
    &gt;&gt;&gt; x = 0.2 
    &gt;&gt;&gt; y - (y % x)
    1.2000000000000002

Dealing with float precision in Javascript

In Java, I want to take a double value and convert it to a `BigDecimal` and print out its String value to a certain precision.  

    import java.math.BigDecimal;
    public class Main {
        public static void main(String[] args) {
            double d=-.00012;
            System.out.println(d+&quot;&quot;); //This prints -1.2E-4
           
            double c=47.48000;
            BigDecimal b = new BigDecimal(c);
            System.out.println(b.toString()); 
            //This prints 47.47999999999999687361196265555918216705322265625 
        }
    }

It prints this huge thing:

&gt; 47.47999999999999687361196265555918216705322265625

and not

&gt;47.48

The reason I&#39;m doing the `BigDecimal` conversion is sometimes the double value will contain a lot of decimal places (i.e. `-.000012`) and the when converting the double to a String will produce scientific notation `-1.2E-4`.  I want to store the String value in non-scientific notation. 

I want to have BigDecimal always have two units of precision like this: &quot;47.48&quot;.  Can BigDecimal restrict precision on conversion to string?


Convert double to BigDecimal and set BigDecimal Precision

I&#39;m having some problems formatting the decimals of a double. If I have a double value, e.g. 4.0, how do I format the decimals so that it&#39;s 4.00 instead?

Content Type	Original Author	Original Content on Stackoverflow
Question	Wouter Dorgelo	View Question on Stackoverflow
Solution 1 - C#	Jon	View Answer on Stackoverflow
Solution 2 - C#	neilgmacy	View Answer on Stackoverflow
Solution 3 - C#	David	View Answer on Stackoverflow
Solution 4 - C#	Evdzhan Mustafa	View Answer on Stackoverflow
Solution 5 - C#	user146043	View Answer on Stackoverflow

Converting a double to an int in C#

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

Solution 4 - C#

Solution 5 - C#

handlerbars.js check if list is empty

How to change text transparency in HTML/CSS?

Attributions