C# – Difference between ASP.net Handler and Generic Handler

asp.netcnet

When we add a new item to an ASP.NET web application project in Visual Studio 2010, I have noticed two templates:

ASP.NET Handler
Generic Handler

What is the difference between these two and when are they used?

Best Answer

Generic handler:

Generic Handler is a default handler which will have @webhandler directive and has .ashx extension this generic handler is not having UI but it provides response when ever any request made to this handler.

HTTP Handler:

HTTP Handler is a process which runs and continue to server request and give response based on the request handling code. This handler does not have UI and need to configured in the web.config against extensions. One of the great example of Http Handler is page handler of ASP.NET which serves .aspx pages request.

The Main difference between Generic and HTTP handler is

Generic handler has a handler which can be accessed by url with .ashx extension while http handler is required to be configured in web.config against extension in web.config.It does not have any extension.Typical example of generic handler are creating thumbnails of images and for http handler page handler which serves .aspx extension request and give response.

To know more refer this link

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – the difference between const and readonly in C#

Apart from the apparent difference of

having to declare the value at the time of a definition for a const VS readonly values can be computed dynamically but need to be assigned before the constructor exits.. after that it is frozen.
const's are implicitly static. You use a ClassName.ConstantName notation to access them.

There is a subtle difference. Consider a class defined in AssemblyA.

public class Const_V_Readonly
{
  public const int I_CONST_VALUE = 2;
  public readonly int I_RO_VALUE;
  public Const_V_Readonly()
  {
     I_RO_VALUE = 3;
  }
}

AssemblyB references AssemblyA and uses these values in code. When this is compiled:

in the case of the const value, it is like a find-replace. The value 2 is 'baked into' the AssemblyB's IL. This means that if tomorrow I update I_CONST_VALUE to 20, AssemblyB would still have 2 till I recompile it.
in the case of the readonly value, it is like a ref to a memory location. The value is not baked into AssemblyB's IL. This means that if the memory location is updated, AssemblyB gets the new value without recompilation. So if I_RO_VALUE is updated to 30, you only need to build AssemblyA and all clients do not need to be recompiled.

So if you are confident that the value of the constant won't change, use a const.

public const int CM_IN_A_METER = 100;

But if you have a constant that may change (e.g. w.r.t. precision).. or when in doubt, use a readonly.

public readonly float PI = 3.14;

Update: Aku needs to get a mention because he pointed this out first. Also I need to plug where I learned this: Effective C# - Bill Wagner

Best Answer

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This is the style that Microsoft tends to use in their examples.

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