Difference bw ref and out key word in c#

The ref keyword is used to pass an argument as a reference.

This means that when value of that parameter is changed in the method,

it gets reflected in the calling method. An argument that is passed using a ref keyword must be initialized in the calling method before it is passed to the called method.

The out keyword is also used to pass an argument like ref keyword,

but the argument can be passed without assigning any value to it.

An argument that is passed using an out keyword must be initialized in the called method before it returns back to calling method.

 

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Reference parameters basically never pass the value of a variable used in the method calling, instead they use the variable themselves. Rather than creating a new storage for that variable in the method declaration, the very same storage space is used, so the value of the variable in the member method and the value of the reference parameter will always be the same. Reference parameters require ref modifier as part of both the declaration and the calling.

Output parameters are very much like reference parameters. The variable specified at the time of calling doesn't need to have been assigned a value before it is passed to the called method. When the method is invoked completely we can read that variable as it is assigned by now.

Like reference parameters, output parameters don't create a new storage location, but use the storage location of the variable specified on the invocation. Output parameters need the out modifier as part of both the declaration and the invocation - that means it's always clear when you're passing something as an output parameter.

 

http://www.dotnetperls.com/parameter

Hi,

Ref

The ref keyword is used to pass an argument as a reference. This means that when value of that parameter is changed in the method, it gets reflected in the calling method. An argument that is passed using a ref keyword must be initialized in the calling method before it is passed to the called method.

Out

The out keyword is also used to pass an argument like ref keyword, but the argument can be passed without assigning any value to it. An argument that is passed using an out keyword must be initialized in the called method before it returns back to calling method.