ref keyword in a function parameter

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Hi
I've been pondering on this matter for some time now...
When is it suggested to use the ref keyword in a function parameter?
I know what it does... To me it is the same as a c style pointer.
It passes the address(reference) to the variable rather than a copy of the variable.

I know that using ref is probebly less resource dependent.
But when is it actually better to rather have a function return above a ref function parameter or visa versa?

Thanks,

Posted 14-Dec-10 21:55pm

R. Erasmus

Updated 14-Dec-10 22:16pm

v2

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Abdul Quader Mamun 15-Dec-10 4:02am

Processor needs input.

4 solutions

Solution 3

A method parameter can be modified by ref regardless of whether it is a value type or a reference type.

There is no boxing of a value type when it is passed by reference.

Posted 14-Dec-10 22:44pm

Kasson

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Abhinav S · Accepted Answer · 2010-12-14T22:35:00

Solution 2

"Do not confuse the concept of passing by reference with the concept of reference types. The two concepts are not the same. A method parameter can be modified by ref regardless of whether it is a value type or a reference type. There is no boxing of a value type when it is passed by reference."

This [^] should answer your queries.

Posted 14-Dec-10 22:35pm

Abhinav S

Comments

R. Erasmus 15-Dec-10 4:49am

what do you mean with "boxing of a value type"?

Abhinav S 15-Dec-10 6:00am

Whenever a value type is converter to a reference type 'boxing' occurs.

R. Erasmus 15-Dec-10 6:08am

Ok I see... Thanks!
Why would you use the 'ref' keyword with a reference type then, or is a reference type actually the equivalent of a c style: "const char*"?

Venkatesh Mookkan · Accepted Answer · 2010-12-14T22:33:00

Solution 1

It depends.

Most of the existings APIs always uses "ref" based functions and also returns value.

Posted 14-Dec-10 22:33pm

Venkatesh Mookkan

Abdul Quader Mamun · Accepted Answer · 2010-12-14T23:19:00

Thank you for your question.

Say you have a big method. This method performs various works step by step. You want to show progress in every stage. You will call this method by a button click like btnCalculateInterest. How you show progress to your calling method. This is not possible by return value in every stage to calling method. You have to perform all the tasks in CalculateInterest method then return. To provide this type solution you need ref.

Example:

C#

private void CalculateInterest(ref int i)
{
    //Step 1
    i=10;
    CalculateLoadAccountsInterest();
    //Step 2
    i=20;
    CalculateDepositAccountsInterest();
    //Step 3
    i=30;
    CalculateCustomerAccountsInterest();
    //Step 4
    i=40;
    CalculateFDRAccountsInterest();
    //So on..

}

protected void btnCalculateInterest_Click(object sender, EventArgs e)
{
  int val = 1;
  CalculateInterest(ref val );
  lblStatus.Text="Progress " + val.ToString() + " percentage or something" ;
}

Thanks,
Mamun