C# – difference between HttpContext and HttpRequest

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HttpRequest represents http client on server as per http://msdn.microsoft.com/en-us/library/system.web.httprequest.aspx it "Enables ASP.NET to read the HTTP values sent by a client during a Web request."

It was my understanding that HttpContext also does the same. As per MSDN http://msdn.microsoft.com/en-us/library/system.web.httpcontext.aspx it is "Encapsulates all HTTP-specific information about an individual HTTP request."

What we need to class for this ? How are they different and which should be used when ?

I am not able to figure out what is difference between them ? Can you please guide and help.

Thanks

Best Answer

HttpRequest is a subset of HttpContext. In other words, the HttpContext includes the response, the request, and various other data that's not relevant to a specific request or response; such as the web application, cached data, server settings and variables, session state, the authenticated user, etc.

For example:

HttpContext.Current.Request // This is the current HttpRequest object
HttpContext.Current.Response // This is the current HttpResponse object

I think if you dig around the APIs of each, you'll quickly understand how things are organized.

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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