Skip to main content

The difference between out and ref in C#


Both the parameters passed by reference,
A ref parameter must first be initialized before being passed from the calling function to the called function.
But a out parameter need not be initialized, we can pass it directly
Normally while we are passing values to other methods it will pass copy of the values.

But we use ref or out Parameter it passes reference of values.
ref and out both allow the called method to modify a parameter. The difference between them is what happens before you make the call.
  • ref means that the parameter has a value on it before going into the function. The called function can read and or change the value any time. The parameter goes in, then comes out
  •  out means that the parameter has no official value before going into the function. The called function must initialize it. The parameter only goes out
Here's a more detailed list of the effects of each alternative:

Before calling the method:

ref: The called must set the value of the parameter before passing it to the called method.
out: The caller method is not required to set the value of the argument before calling the method. Most likely, you shouldn't. In fact, any current value is discarded.

During the call:

ref: The called method can read the argument at any time.
out: The called method must initialize the parameter before reading it.

Remoted calls:

ref: The current value is marshalled to the remote call. Extra performance cost.
out: Nothing is passed to the remote call. Faster.
Technically speaking, you could use always ref in place of out, but out allows you to be more precise about the meaning of the argument, and sometimes it can be a lot more efficient.

Example


public class Test
{
    public void TestRef(ref int value)
    {
        value = 20;
    }
    public void TestOut(out int value)
    {
        value = 30;
    }
}
//--ref
Test ObjTest = new Test();
int value1=10;
Response.Write("Before ref:"+value1);
ObjTest.TestRef(ref value1);
Response.Write("After ref:"+value1);

//--Out
int value2;
ObjTest.TestOut(out value2);
Response.Write("After Out :" + value2);

OUTPUT
Before ref : 10
After ref : 20
After Out : 30

Comments

Popular posts from this blog

Connected and disconnected architecture in ADO.Net with Example

Connected Architecture of ADO.NET The architecture of ADO.net, in which connection must be opened to access the data retrieved from database is called as connected architecture. Connected architecture was built on the classes connection, command, datareader and transaction.  Connected architecture is when you constantly make trips to the database for any CRUD (Create, Read, Update and Delete) operation you wish to do. This creates more traffic to the database but is normally much faster as you should be doing smaller transactions. Disconnected Architecture in ADO.NET The architecture of ADO.net in which data retrieved from database can be accessed even when connection to database was closed is called as disconnected architecture. Disconnected architecture of ADO.net was built on classes connection, dataadapter, commandbuilder and dataset and dataview. Disconnected architecture is a method of retrieving a recor

HTTPHandler and HTTPModule in ASP.NET

If you want to implement pre-processing logic before a request hits the IIS resources. For instance you would like to apply security mechanism, URL rewriting, filter something in the request, etc. ASP.NET has provided two types of interception HttpModule and HttpHandler .   The web server examines the file name extension of the requested file, and determines which ISAPI extension should handle the request. Then the request is passed to the appropriate ISAPI extension.  For Example When an .aspx page is requested it is passed to ASP.Net page handler. Then Application domain is created and after that different ASP.Net objects like Httpcontext, HttpRequest, HttpResponse. HTTPModule: -    It's just like a filter. The Modules are called before and after the handler executes . -    HTTP Modules are objects which also participate the pipeline but they work before and after the HTTP Handler does its job, and produce additional services within the pipeline -  

ASP.NET Page Life Cycle with example

In this article, we are going to discuss the different methods and order they are executed during the load of an .aspx web page. Methods Description Page_PreInit Before page Initialization Page_Init Page Initialization LoadViewState View State Loading LoadPostData Postback Data Processing Page_Load Page Loading RaisePostDataChangedEvent PostBack Change Notification RaisePostBackEvent PostBack Event Handling Page_PreRender Page Pre Rendering Phase SaveViewState View State Saving Page_Render Page Rendering Page_Unload Page Unloading PreInit : The entry point of the page life cycle is the pre-initialization phase called “PreInit”. You can dynamically set the values of master pages and themes in this event. You can also dynamically create controls in this event.  Init : This event fires after each control h