`System.Enum` is a reference type, but any *specific* enum type is a value type. In the same way, `System.ValueType` is a reference type, but all types inheriting from it (other than `System.Enum`) are value types.

So if you have an enum `Foo` and you want a nullable property, you need the property type to be `Foo?`.

If you do `myEnum.SomeValue` it will be a value type.

suppose we have enum

    public enum eCategory
    {
    	health ,		
    	Weapon
    }

and a type of eCategory such as :-

    eCategory currentcategory;

then currentcategory is of value type



    public enum TestReferenceOrValue
    {
        one, two, three    
    }
    var a = TestReferenceOrValue.one;
    var b = a;
    b = TestReferenceOrValue.three;
If enums are by reference, changing `b` affects `a`    
`Console.Write(a);` → one  
`Console.Write(b);` → three  

a great online tool for cSharp =&gt; [http://csharppad.com/][1]


  [1]: http://csharppad.com/

For C programming. How do i get numbers to be displayed as 00, 01, 02, 03, instead of 0, 1, 2, 3. I just need 0 before the number until 10.

i know when your doing decimals you can do &quot;%.2f&quot; etc. but what about in reverse for integers?

here is what I am using...**


    printf(&quot;Please enter the hours: &quot;);
        scanf (&quot;%d&quot;,&amp;hour);
    printf(&quot;Please enter the minutes: &quot;);
        scanf (&quot;%d&quot;,&amp;minute);
    printf(&quot;Please enter the seconds: &quot;);
        scanf (&quot;%d&quot;,&amp;second);
    printf(&quot;%d : %d : %d\n&quot;, hour, minute, second);



}

I need the numbers to display as 00 : 00 : 00

??


How do get numbers to display as two digits in C?

Is there a difference between

    int[] array = new int[10];

and

    int array[] = new int[10];

?

Both do work, and the result is exactly the same. Which one is quicker or better? Is there a style guide which recommends one?


Java: int[] array vs int array[]

I used Enum property in my [EntityFramework][1] 5 class,
but in the database this field is nullable. Visual studio gives the error that this property must be a nullable property. My question is: is Enum a reference type or a value type?


  [1]: http://msdn.microsoft.com/en-US/data/ef

Enum is Reference Type or Value Type?

<p>I used Enum property in my <a href="http://msdn.microsoft.com/en-US/data/ef" target="_blank" rel="noopener noreferrer">EntityFramework</a> 5 class,
but in the database this field is nullable. Visual studio gives the error that this property must be a nullable property. My question is: is Enum a reference type or a value type?</p>


I want to make some `TextBox`es on my form uneditable, but I want the `text` to be clear (black not gray) and that&#39;s why I do not want to use  

   `myTextBox.Enabled = false;`

Somehow I want it to be disabled but with non-gray fore-color.

Does anyone have any clue?

Make TextBox uneditable

I have an ASP.NET MVC3 C# .NET Application running on IIS 7.5.  

We have a Windows NT service account we Impersonate in our code in order to read/write documents to a file share. The user id is compiled in the code and the service account password is stored in the web.config file.  

The password contains an ampersand character (i.e.: `p&amp;ssword`).  

This broke the site.  When accessing the site we received this error :&quot;Sorry, an error occurred while processing your request&quot;.  

Here is the code that uses the password:

        var password = ConfigurationManager.AppSettings.Get(Common.SVC_PWD);

        bool isSuccess = LogonUser(
            @&quot;my_svc_acct&quot;,
            &quot;my.domain.net&quot;,
            password,
            LOGON32_LOGON_NEW_CREDENTIALS,
            LOGON32_PROVIDER_DEFAULT, ref token
        );

Why would this cause the site to break?

The &quot;&amp;&quot; character breaks passwords that are stored in the web.config

I used to use these in NUnit and they are really useful. Any idea how to do something like that?

EDIT, CODE SAMPLE:

            bool condition = false;//would be nice not to have this
            observable.Subscribe(_ =&gt;
            {
                if (real test)
                    condition= true;//Assert.Pass()
            });
            StartObservable();
            Assert.True(condition);//Assert.Fail()      

Cannot find Assert.Fail and Assert.Pass or equivalent

I have written a few C# apps that I have running via windows task scheduler. They are running successfully (as I can see from the log files that they are writing ) but windows task scheduler shows them returning a last run result of `0xE0434352`. Is there something I need to do in my C# application so that it returns a success code to the windows task scheduler?


My C# application is returning 0xE0434352 to Windows Task Scheduler but it is not crashing

Suppose I have a .net Array of strings.

    string[] strings = new string[] { &quot;AbC&quot;, &quot;123&quot;, &quot;Xyz&quot;, &quot;321&quot; };

If I wanted to see if the array of strings contains &quot;ABC&quot;, I could write

    strings.Contains(&quot;ABC&quot;);

However, suppose that I want a function that will return true if the uppercase values of the strings contain &quot;ABC&quot;.  I could uppercase the entire array, but it looks like the `.Contains` method has some overloads for specifying the comparison, but I&#39;m confused by the syntax.

How can I use the `IEnumerable&lt;string&gt;.Contains()` method implement this logic?

How to make IEnumerable&lt;string&gt;.Contains case-insensitive?

What I try to do is this:

    public class History {
    	public class State {
    		public enum StateType {

Eclipse gives me this compile error on `StateType`: `The member enum StateType must be defined inside a static member type`.

The error disappears when I make the `State` class static. I could make `State` static, but I don&#39;t understand why I cannot declare an `enum` in an inner class.

Why can&#39;t I create an enum in an inner class in Java?

How do I convert the following Enum to a List of strings?

    [Flags]
    public enum DataSourceTypes
    {
        None = 0,
        Grid = 1,
        ExcelFile = 2,
        ODBC = 4
    };

I couldn&#39;t find this exact question, this [Enum to List](https://stackoverflow.com/questions/1167361/how-do-i-convert-an-enum-to-a-list-in-c) is the closest but I specifically want `List&lt;string&gt;`

Convert an enum to List&lt;string&gt;

I can&#39;t figure out how to use switches in combination with an enum. Could you please tell me what I&#39;m doing wrong, and how to fix it? I have to use an enum to make a basic calculator. 


    public enum Operator
    {
        PLUS, MINUS, MULTIPLY, DIVIDE
    }

    public double Calculate(int left, int right, Operator op)
    {

        int i = (int) op;

        switch(i)
        {
            case 0:
            {
                return left + right;
            }

            case 1:
            {
                return left - right;
            }

            case 2:
            { 
                return left * right;
            }

            case 3:
            {
                return left / right;
            }

            default:
            {
                return 0.0;
            }
        }
    }

The end result should be something like this:

    Console.WriteLine(&quot;The sum of 5 and 5 is &quot; + Calculate(5, 5, PLUS))
    Output: The sum of 5 and 5 is 10

Could you guys please tell me how I&#39;m messing up?

C# how to use enum with switch

I have this Enum code:

    enum Duration { Day, Week, Month };

Can I add a extension methods for this Enum?

How to add extension methods to Enums

I have a MySQL table &quot;`content`&quot; which has a column `page_type` of type `ENUM`. The `ENUM` values are `NEWS` &amp; `PRESS_RELEASE`.  I need to replace `NEWS` with `FEATURED_COVERAGE`:

    ALTER TABLE `content` CHANGE `pagetype` `pagetype` ENUM(&#39;FEATURED_COVERAGE&#39;,&#39;PRESS_RELEASE&#39;) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL;

But now the records in the table, which earlier had page_type `NEWS` are now empty, and there is no way that I can identify which records are `NEWS`, so that I can rename those to `FEATURED_COVERAGE`.

How to resolve such issues?

MySQL Change a column ENUM value

Apparently you can change the `this` value from anywhere in your struct (but not in classes):

	struct Point
	{
		public Point(int x, int y)
		{
			this = new Point();
			X = x; Y = y;
		}
		int X; int Y;
	}

I&#39;ve neither seen this before nor ever needed it. Why would one ever want to do that? [Eric Lippert reminds us](https://stackoverflow.com/a/4914207/146622) that a feature must be justified to be implemented. What great use case could justify this? Are there any scenarios where this is invaluable? &lt;s&gt;I couldn&#39;t find any documentation on it&lt;/s&gt;&lt;sup&gt;1&lt;/sup&gt;.

Also, for calling constructors there is already a better known alternative syntax, so this feature is sometimes redundant:

	public Point(int x, int y)
		: this()
	{
		X = x; Y = y;
	}

&lt;sub&gt;I found this feature in an example in Jeffrey Richter&#39;s [CLR via C# 4th edition](http://www.amazon.com/CLR-via-Microsoft-Developer-Reference/dp/0735667454).&lt;/sub&gt;&lt;br /&gt;
&lt;sub&gt;1) Apparently it is in the [C# specification](https://stackoverflow.com/a/14767499/146622).&lt;/sub&gt;

Changing the &#39;this&#39; variable of value types

There is something that I don&#39;t entirely understand when it comes to mutating value types in Swift.

As the &quot;The Swift Programming Language&quot; iBook states:  ***By default, the properties of a value type cannot be modified from within its instance methods.***

And so to make this possible we can declare methods with the `mutating` keyword inside structs and enums.

The thing that is not entirely clear to me is this:
You can change a var from outside a struct, but you cannot change it from its own methods. This seems counter-intuitive to me, as in Object Oriented languages, you generally try to encapsulate variables so they can only be changed from within. With structs this appears to be the other way around. To elaborate, here&#39;s a code snippet:

    struct Point {
        var x = 0, y = 0
        mutating func moveToX(x: Int, andY y:Int) { //Needs to be a mutating method in order to work
            self.x = x
            self.y = y
        }
    }

    var p = Point(x: 1, y: 2)
    p.x = 3 //Works from outside the struct!
    p.moveToX(5, andY: 5) 



Does anyone know the reason why structs cannot change their content from inside their own context, while the contents can easily be changed elsewhere?

Swift and mutating struct

I don&#39;t understand when to use `AnyObject` and when to use `Any` in Swift.

In my case, I&#39;ve a `Dictionary`

&gt; [String: ???]

??? : Can be `Int`, `Double`, `Float`, `String`, `Array`, `Dictionary`

Can someone explain me the difference between `Any` and `AnyObject`
and which one to use in my case.


AnyObject and Any in Swift

This is a weird behaviour that I cannot make sense of. In my example I have a class `Sample&lt;T&gt;` and an implicit conversion operator from `T` to `Sample&lt;T&gt;`. 

    private class Sample&lt;T&gt;
    {
       public readonly T Value;

       public Sample(T value)
       {
          Value = value;
       }

       public static implicit operator Sample&lt;T&gt;(T value) =&gt; new Sample&lt;T&gt;(value);
    }

The problem occurs when using a nullable value type for `T` such as `int?`. 

    {
       int? a = 3;
       Sample&lt;int&gt; sampleA = a;
    }

**Here is the key part:**  
In my opinion this should not compile because `Sample&lt;int&gt;` defines a conversion from `int` to `Sample&lt;int&gt;` but not from `int?` to `Sample&lt;int&gt;`. **But it compiles and runs successfully!** (By which I mean the conversion operator is invoked and `3` will be assigned to the `readonly` field.)

And it gets even worse. Here the conversion operator isn&#39;t invoked and `sampleB` will be set to `null`:

    {
       int? b = null;
       Sample&lt;int&gt; sampleB = b;
    }

A great answer would probably be split into two parts:

1. Why does the code in the first snippet compile?
2. Can I prevent the code from compiling in this scenario?

Content Type	Original Author	Original Content on Stackoverflow
Question	user1318951	View Question on Stackoverflow
Solution 1 - .Net	Jon Skeet	View Answer on Stackoverflow
Solution 2 - .Net	fhnaseer	View Answer on Stackoverflow
Solution 3 - .Net	Eklavyaa	View Answer on Stackoverflow
Solution 4 - .Net	SAm	View Answer on Stackoverflow

Enum is Reference Type or Value Type?

.Net Problem Overview

.Net Solutions

Solution 1 - .Net

Solution 2 - .Net

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Java: int[] array vs int array[]

How do get numbers to display as two digits in C?

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