April 29. 2010 10:45 AM

the more practical example would be this:

MyObject instance;
if ((instance = TryGetMeMyObject()) != null)
{
}

Donatas

April 29. 2010 11:06 AM

Erm ... I don't get it, what did you expect that it would return? What other option is there?

Donatas:
Why is your example more practical?

Dalibor Carapic

April 29. 2010 04:06 PM

If you think of the assignment as a method call it becomes more obvious that the assignment happens before the return:

return a.Assign( "hello" );

Martin Ennemoser

April 29. 2010 05:14 PM

I know in C++ if you do

if (a = "hello")

it will return true, because the assignment was successful.  I kind of expected the same thing from C# code.  I've never tried returning a = "hello" in C++ though.  I wonder if it returns true or the value of a in that language.

Billkamm

April 29. 2010 09:09 PM

I failed to see the point.  Isn't that part of the operator precedence?  Since 'return' is an operator, the assignment will be evaluated before the return gets evaluated since the assignment operator has higher precedence then return.

What am I missing here?

mchiao

April 29. 2010 09:48 PM

Eh... No shit Sherlock!

Ray

April 30. 2010 01:30 AM

I've used this trick on properties before, to always guarantee that a member variable, when accessed is initialized

private IList<SomeObject> _someList;
public IList<SomeObject> SomeObjects
{
    get { return _someList ?? _someList = new List<SomeObject>(); }
}

Jon Erickson

May 11. 2010 08:40 PM

Here's another practical example:

using (StreamReader reader = new StreamReader("file.txt"))
{
    string line;
    while ((line = reader.ReadLine()) != null)
    {
        list.Add(line);          // Add to list.
        Console.WriteLine(line); // Write to console.
    }
}

Chinh Do

May 26. 2010 10:18 PM

@Billkamm

>> if (a = "hello") will return true, because the assignment was
>> successful.

um.. no..  '(a="hello")' actually evaluates to a pointer to the string "Hello".  That pointer is then silently checked to see if it is not null, and that comparison would be determined to be true.

However, if you wrote 'if(a = null)' that would evaluate to false (since the expression is not "not null").  Since it is easy to write that by mistake when you meant "if (a == null)", many developers wrote that expression as "if (null == a)" which will generate a syntax error if you forget an equals sign.

James Curan

April 12. 2012 10:08 AM

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