Look at Activator.CreateInstance().

    myObject = (MyAbstractClass)Activator.CreateInstance(&quot;AssemblyName&quot;, &quot;TypeName&quot;);


or

    var type = Type.GetType(&quot;MyFullyQualifiedTypeName&quot;);
    var myObject = (MyAbstractClass)Activator.CreateInstance(type);





I believe this should work:

    myObject = (MyAbstractClass)Activator.CreateInstance(null, childClassString);

The `null` in the first parameter defaults to the current executing assembly. For more reference: [MSDN][1]


edit: forgot to cast to `MyAbstractClass`

  [1]: http://msdn.microsoft.com/en-us/library/d133hta4.aspx

I had some difficulty implementing some of the answers here because I was trying to instantiate an object from a different assembly (but in the same solution).  So I thought I&#39;d post what I found to work.

First, the `Activator.CreateInstance` method has several overloads.  If you just call `Activator.CreateInstance(Type.GetType(&quot;MyObj&quot;))`, that assumes the object is defined in the current assembly, and it returns a `MyObj`.

If you call it as recommended in the answers here: `Activator.CreateInstance(string AssemblyName, string FullyQualifiedObjectName)`, then it instead returns an `ObjectHandle`, and you need to call `Unwrap()` on it to get your object.  This overload is useful when trying to call a method defined in a different assembly (BTW, you can use this overload in the current assembly, just leave the `AssemblyName` parameter null).

Now, I found that the suggestion above to use `typeof(ParentNamespace.ChildNamespace.MyObject).AssemblyQualifiedName`  for `AssemblyName` actually gave me errors, and I could not get that to work.  I&#39;d get `System.IO.FileLoadException` (could not load file or assembly...).

What I did get to work is as follows:

    var container = Activator.CreateInstance(@&quot;AssemblyName&quot;,@&quot;ParentNamespace.ChildNamespace.MyObject&quot;);
    MyObject obj = (MyObject)container.Unwrap();
    obj.DoStuff();



Given a simple zero based, numerically indexed array:

    var list = [&#39;Foo&#39;, &#39;Bar&#39;, &#39;Baz&#39;];

Many times, I have noticed that when someone suggests looping through variables in an array like this:

    for(var item in list) { ... }

...there&#39;s almost certainly someone suggesting that that&#39;s bad practice and suggests an alternative approach:

    var count = list.length;
   
    for(var i = 0; i &lt; count; i++) {
        var item = list[i];
        ...
    }

What&#39;s the reasoning for not using the simpler version above and to use the second example instead?

Why is &#39;for(var item in list)&#39; with arrays considered bad practice in JavaScript?

I want to iterate over the alphabet like so:

    foreach(char c in alphabet)
    {
     //do something with letter
    }

Is an array of chars the best way to do this? (feels hacky)

Edit: The metric is &quot;least typing to implement whilst still being readable and robust&quot;

Quickest way to enumerate the alphabet

I have an abstract class and I want to initalize it to a class that extends it.

I have the child classes name as a string.

Besides this...

    String childClassString;
    MyAbstractClass myObject;
    
    if (childClassString = &quot;myExtenedObjectA&quot;)
        myObject = new ExtenedObjectA();
    if (childClassString = &quot;myExtenedObjectB&quot;)
        myObject = new ExtenedObjectB();

How can I do this? Basically how do I get rid of the if statements here?

How do I instantiate a class given its string name?

I have an abstract class and I want to initalize it to a class that extends it.
I have the child classes name as a string.
Besides this...
<pre><code class="hljs language-ini">String childClassString;
MyAbstractClass myObject;

if (childClassString = "myExtenedObjectA")
 myObject = new ExtenedObjectA();
if (childClassString = "myExtenedObjectB")
 myObject = new ExtenedObjectB();
</code></pre>
How can I do this? Basically how do I get rid of the if statements here?

I have created an application ([C#][1], [Windows Forms][2]) on [Visual&amp;nbsp;Studio&amp;nbsp;2008][3], and now I want to make installer of this application. How can this be done?

I want my installer to 

 - Copy all the files that my
   application is using to a user
   chosen path (copy the files to
   the chosen, some for the server-side application and
   some for the client side).
 - Also install [.NET][4] 3.5 
 - Check for [SQL&amp;nbsp;Server][5] or [SQL Server Express Edition][6]

How can I do it?

  [1]: http://en.wikipedia.org/wiki/C_Sharp_%28programming_language%29
  [2]: http://en.wikipedia.org/wiki/Windows_Forms
  [3]: http://en.wikipedia.org/wiki/Microsoft_Visual_Studio#Visual_Studio_2008
  [4]: http://en.wikipedia.org/wiki/.NET_Framework
  [5]: http://en.wikipedia.org/wiki/Microsoft_SQL_Server
  [6]: http://en.wikipedia.org/wiki/SQL_Server_Express


How to make an installer for my C# application?

In MSDN, the description of the Thread.Abort() method says: &quot;Calling this method **usually** terminates the thread.&quot; 

Why not ALWAYS? 

In which cases it doesn&#39;t terminate the thread? 

Are there any other possibility to terminate threads?

C# Thread Termination and Thread.Abort()

I am attempting to install a C# windows service project using a VisualStudio.Net deployment project.  

To run the deployment project I right-click and select &quot;install&quot; from the context menu, the install wizard runs and eventually prompts me with a &quot;Set Service Login&quot; dialog which asks for username &amp; password.  

When I install a service using the sc utility from the command line, I don&#39;t have to provide credentials.

Do I have to create a login just for this service?  I&#39;d prefer to use &quot;Local System&quot; or &quot;Network Service&quot; (not sure what the difference is) as other services do.

Credentials when Installing Windows Service

I need help putting together a regex that will match word that ends with &quot;Id&quot; with case sensitive match.

Regex: match word that ends with &quot;Id&quot;

I think I have my brain halfway wrapped around the Dynamic Types concept in C# 4, but can&#39;t for the life of me figure out a scenario where I&#39;d actually want to use it.

I&#39;m sure there are many, but I&#39;m just having trouble making the connection as to how I could engineer a solution that is better solved with dynamics as opposed to interfaces, dependency injection, etc.

So, what&#39;s a real-world application scenario where dynamic type usage is appropriate?

C# 4: Real-World Example of Dynamic Types

I want to find out via reflection if a field is an instance of some type `T`. 

Lets say I have an object `o`. Now I want to know if it has any fields which are instance of `T`. I can get all fields with:

    o.getClass().getFields();

I can get the type of the field with:

    field.getType();

But now I want to know if this type or any supertype equals `T`. Do I have to call `getSuperclass()` recursively to be sure to check all supertypes?


How to find out if a field is instanceof a type via reflection?

I have a type, `t`, and I would like to get a list of the public properties that have the attribute `MyAttribute`. The attribute is marked with `AllowMultiple = false`, like this:

    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]

Currently what I have is this, but I&#39;m thinking there is a better way:

    foreach (PropertyInfo prop in t.GetProperties())
    {
        object[] attributes = prop.GetCustomAttributes(typeof(MyAttribute), true);
        if (attributes.Length == 1)
        {
             //Property with my custom attribute
        }
    }
How can I improve this? My apologies if this is a duplicate, there are a ton of reflection threads out there...seems like it&#39;s quite a hot topic.

How to get a list of properties with a given attribute?

Is there a built in method, function, API, commonly accepted way, etc. to dump the contents of an instantiated object in Objective-C, specifically in Apple&#39;s Cocoa/Cocoa-Touch environment?

I want to be able to do something like

	MyType *the_thing = [[MyType alloc] init];
	NSString *the_dump = [the_thing dump]; //pseudo code
	NSLog(&quot;Dumped Contents: %@&quot;, the_dump);
	
and have the object&#39;s instance variable names and values displayed, along with any methods available to call at run time. Ideally in an easy to read format.

For developers familiar with PHP, I&#39;m basically looking for the equivalent of the reflection functions (`var_dump()`, `get_class_methods()`) and the OO Reflection API. 


Objective-C Introspection/Reflection

I am trying to get a string name of a class from the class object itself.

    // For instance
    [NSArray className]; // @&quot;NSArray&quot;

I have found `object_getClassName(id obj)` but that requires an instance be passed to it, and in my case that is needless work.

So how can I get a string from a class object, and _not_ an instance?

Objective-C class -&gt; string like: [NSArray className] -&gt; @&quot;NSArray&quot;

The project I&#39;m working on needs some simple audit logging for when a user changes their email, billing address, etc.  The objects we&#39;re working with are coming from different sources, one a WCF service, the other a web service.

I&#39;ve implemented the following method using reflection to find changes to the properties on two different objects.  This generates a list of the properties that have differences along with their old and new values.


&lt;pre&gt;&lt;code&gt;public static IList&lt;string&gt; GenerateAuditLogMessages&lt;T&gt;(T originalObject, T changedObject)
{
    IList&lt;string&gt; list = new List&lt;string&gt;();
    string className = string.Concat(&quot;[&quot;, originalObject.GetType().Name, &quot;] &quot;);

    foreach (PropertyInfo property in originalObject.GetType().GetProperties())
    {
        Type comparable =
            property.PropertyType.GetInterface(&quot;System.IComparable&quot;);
    
        if (comparable != null)
        {
            string originalPropertyValue =
                property.GetValue(originalObject, null) as string;
            string newPropertyValue =
                property.GetValue(changedObject, null) as string;
    
            if (originalPropertyValue != newPropertyValue)
            {
                list.Add(string.Concat(className, property.Name,
                    &quot; changed from &#39;&quot;, originalPropertyValue,
                    &quot;&#39; to &#39;&quot;, newPropertyValue, &quot;&#39;&quot;));
            }
        }
    }

    return list;
}&lt;/code&gt;&lt;/pre&gt;


I&#39;m looking for System.IComparable because &quot;All numeric types (such as Int32 and Double) implement IComparable, as do String, Char, and DateTime.&quot;  This seemed the best way to find any property that&#39;s not a custom class.

Tapping into the PropertyChanged event that&#39;s generated by the WCF or web service proxy code sounded good but doesn&#39;t give me enough info for my audit logs (old and new values).

Looking for input as to if there is a better way to do this, thanks!



@Aaronaught, here is some example code that is generating a positive match based on doing object.Equals:

&lt;pre&gt;&lt;code&gt;Address address1 = new Address();
address1.StateProvince = new StateProvince();

Address address2 = new Address();
address2.StateProvince = new StateProvince();

IList&lt;string&gt; list = Utility.GenerateAuditLogMessages&lt;Address&gt;(address1, address2);&lt;/code&gt;&lt;/pre&gt;



&gt; &quot;[Address] StateProvince changed from
&gt; &#39;MyAccountService.StateProvince&#39; to
&gt; &#39;MyAccountService.StateProvince&#39;&quot;

It&#39;s two different instances of the StateProvince class, but the values of the properties are the same (all null in this case).  We&#39;re not overriding the equals method.

Finding property differences between two C# objects

    // Cannot change source code
	class Base
	{
		public virtual void Say()
		{
			Console.WriteLine(&quot;Called from Base.&quot;);
		}
	}

	// Cannot change source code
	class Derived : Base
	{
		public override void Say()
		{
			Console.WriteLine(&quot;Called from Derived.&quot;);
			base.Say();
		}
	}

	class SpecialDerived : Derived
	{
		public override void Say()
		{
			Console.WriteLine(&quot;Called from Special Derived.&quot;);
			base.Say();
		}
	}

	class Program
	{
		static void Main(string[] args)
		{
			SpecialDerived sd = new SpecialDerived();
			sd.Say();
		}
	}

The result is:

&gt; Called from Special Derived.  
&gt; Called from Derived. /* this is not expected */  
&gt; Called from Base.

How can I rewrite SpecialDerived class so that middle class &quot;Derived&quot;&#39;s method is not called?

**UPDATE:**
The reason why I want to inherit from Derived instead of Base is Derived class contains a lot of other implementations. Since I can&#39;t do `base.base.method()` here, I guess the best way is to do the following?

  &lt;strike&gt;// Cannot change source code&lt;/strike&gt;

    class Derived : Base
    {
        public override void Say()
        {
            CustomSay();

            base.Say();
        }

        protected virtual void CustomSay()
        {
            Console.WriteLine(&quot;Called from Derived.&quot;);
        }
    }

    class SpecialDerived : Derived
    {
        /*
        public override void Say()
        {
            Console.WriteLine(&quot;Called from Special Derived.&quot;);
            base.Say();
        }
        */

        protected override void CustomSay()
        {
            Console.WriteLine(&quot;Called from Special Derived.&quot;);
        }
    }

How to call base.base.method()?

I&#39;m learning C++ and I&#39;m just getting into virtual functions.

From what I&#39;ve read (in the book and online), virtual functions are functions in the base class that you can override in derived classes.

But earlier in the book, when learning about basic inheritance, I was able to override base functions in derived classes without using `virtual`.

So what am I missing here? I know there is more to virtual functions, and it seems to be important so I want to be clear on what it is exactly. I just can&#39;t find a straightforward answer online.



Why do we need virtual functions in C++?

My code below won&#39;t compile. What am i doing wrong? I&#39;m basically trying to have a public constant that is overridden in the base class.

    public abstract class MyBaseClass
    {
      public abstract const string bank = &quot;???&quot;;
    }

    public class SomeBankClass : MyBaseClass
    {
      public override const string bank = &quot;Some Bank&quot;;
    }

Thanks as always for being so helpful!

How to have abstract and overriding constants in C#?

I&#39;m a bit confused about how Java generics handle inheritance / polymorphism.

Assume the following hierarchy -

**Animal** (Parent)

**Dog** - **Cat** (Children)

So suppose I have a method `doSomething(List&lt;Animal&gt; animals)`. By all the rules of inheritance and polymorphism, I would assume that a `List&lt;Dog&gt;` *is* a `List&lt;Animal&gt;` and a `List&lt;Cat&gt;` *is* a `List&lt;Animal&gt;` - and so either one could be passed to this method. Not so. If I want to achieve this behavior, I have to explicitly tell the method to accept a list of any subclass of Animal by saying `doSomething(List&lt;? extends Animal&gt; animals)`. 

I understand that this is Java&#39;s behavior. My question is *why*? Why is polymorphism generally implicit, but when it comes to generics it must be specified?


Is List&lt;Dog&gt; a subclass of List&lt;Animal&gt;? Why are Java generics not implicitly polymorphic?

Having a chain of &quot;instanceof&quot; operations is considered a &quot;code smell&quot;.  The standard answer is &quot;use polymorphism&quot;.  How would I do it in this case?

There are a number of subclasses of a base class; none of them are under my control.  An analogous situation would be with the Java classes Integer, Double, BigDecimal etc.

    if (obj instanceof Integer) {NumberStuff.handle((Integer)obj);}
    else if (obj instanceof BigDecimal) {BigDecimalStuff.handle((BigDecimal)obj);}
    else if (obj instanceof Double) {DoubleStuff.handle((Double)obj);}

I do have control over NumberStuff and so on.

I don&#39;t want to use many lines of code where a few lines would do.  (Sometimes I make a HashMap mapping Integer.class to an instance of IntegerStuff, BigDecimal.class to an instance of BigDecimalStuff etc.  But today I want something simpler.)

I&#39;d like something as simple as this:

    public static handle(Integer num) { ... }
    public static handle(BigDecimal num) { ... }

But Java just doesn&#39;t work that way.

I&#39;d like to use static methods when formatting.  The things I&#39;m formatting are composite, where a Thing1 can contain an array Thing2s and a Thing2 can contain an array of Thing1s.  I had a problem when I implemented my formatters like this:

    class Thing1Formatter {
      private static Thing2Formatter thing2Formatter = new Thing2Formatter();
      public format(Thing thing) {
          thing2Formatter.format(thing.innerThing2);
      }
    }
    class Thing2Formatter {
      private static Thing1Formatter thing1Formatter = new Thing1Formatter();
      public format(Thing2 thing) {
          thing1Formatter.format(thing.innerThing1);
      }
    }

Yes, I know the HashMap and a bit more code can fix that too.  But the &quot;instanceof&quot; seems so readable and maintainable by comparison.  Is there anything simple but not smelly?

Note added 5/10/2010:

It turns out that new subclasses will probably be added in the future, and my existing code will have to handle them gracefully.  The HashMap on Class won&#39;t work in that case because the Class won&#39;t be found.  A chain of if statements, starting with the most specific and ending with the most general, is probably the best after all:

    if (obj instanceof SubClass1) {
        // Handle all the methods and properties of SubClass1
    } else if (obj instanceof SubClass2) {
        // Handle all the methods and properties of SubClass2
    } else if (obj instanceof Interface3) {
        // Unknown class but it implements Interface3
        // so handle those methods and properties
    } else if (obj instanceof Interface4) {
        // likewise.  May want to also handle case of
        // object that implements both interfaces.
    } else {
        // New (unknown) subclass; do what I can with the base class
    }


Content Type	Original Author	Original Content on Stackoverflow
Question	ctrlShiftBryan	View Question on Stackoverflow
Solution 1 - C#	Seth Petry-Johnson	View Answer on Stackoverflow
Solution 2 - C#	IAbstract	View Answer on Stackoverflow
Solution 3 - C#	Kevin Fichter	View Answer on Stackoverflow

How do I instantiate a class given its string name?

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

Quickest way to enumerate the alphabet

Why is 'for(var item in list)' with arrays considered bad practice in JavaScript?

Attributions