+=

[Peter Kirk]

Hi

a simple question about the meaning of "+=" in C#.

What does something like this mean:
this.TextBox1.TextChanged += new
System.EventHandler(this.TextBox1_TextChanged);

Is it a call to an "add" function or something? (I know that in C# one can
implicitly cause a call to a "get" or a "set" by simply referencing an
instance variable of a class - although I'm not 100% sure of this syntax
either).

Thanks,
Peter

[Daniel O'Connell [C# MVP]]

"Peter Kirk" <[e-mail]> wrote in message
news:%2****************@TK2MSFTNGP10.phx.gbl...

Hi

a simple question about the meaning of "+=" in C#.

What does something like this mean:
this.TextBox1.TextChanged += new
System.EventHandler(this.TextBox1_TextChanged);

the += operator itself, consdiering the code x += y, x = x + y; That is it
adds the left side to the right side and assigns the result to the left.

In respect to events it indeed does attach a delegate to an event via an add
function. Its behaviour isn't exactly like the preceding += operator in that
it doesn't actually assign anything, it just calls the add method.

As a piece of minuta, you can also write events in the following form

event EventHandler TextChanged
{
add
{
//combine delegates
}

remove
{
//remove delegate from delegate list
}
}

The language has a simple way of expressing events when you do not need
special code in these accessors

[Mattias Sjögren]

Is it a call to an "add" function or something?

Yes

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Olaf Baeyens]

> In respect to events it indeed does attach a delegate to an event via an
add

function. Its behaviour isn't exactly like the preceding += operator in that it doesn't actually assign anything, it just calls the add method.

This way it can add multiple delegates to the same event that will be
executed each.