Method chaining with short-circuit parameter evaluation

[szukuro]

Actually to be passed as an expresion tree you'd have to write:

var result = SafeChain(**() =>**A.b.c.d.e.f.g.h.i.j.k);

But I agree that this is the way to do it.

[Brisingr Aerowing]

public static U NotNull<T, U>(this T myObject, Expression<Func<T, U>> expression) where U : class
{

if (myObject == null)
{
    return null;
}

try
{
    var func = expression.Compile();
    return func(myObject);
}
catch (Exception)
{
    return null;
}

}

Based off of a suggestion above. I tested this, and it seems to work.

Bob Dole

The internet is a great way to get on the net.

:doh: 2.0.82.7292 SP6a

[Andrew Rissing]

Maybe this IS the fix for the site.

[Brisingr Aerowing]

I figured out something that works. See my message below. It is based off of yours, with an extra parameter for the expression.

Bob Dole

The internet is a great way to get on the net.

:doh: 2.0.82.7292 SP6a

[Richard Deeming]

If only there was some sort of site where people could write articles on exactly this issue[^]! ;P

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[Paul Conrad]

You could just toss a :thumbsup: in place of a 5 vote.

"I've seen more information on a frickin' sticky note!" - Dave Kreskowiak

[Septimus Hedgehog]

Have you looked at this CP article by Dimitri Nesteruk[^] It looks very useful.

"I do not have to forgive my enemies, I have had them all shot." — Ramón Maria Narváez (1800-68). "I don't need to shoot my enemies, I don't have any." - Me (2012).

[AspDotNetDev]

You were beat to the punch. :)

Thou mewling ill-breeding pignut!

[AspDotNetDev]

Yes! :thumbsup:

Thou mewling ill-breeding pignut!

[Gary Wheeler]

In C++ you could do this with an 'instance' call like this:

if (this != NULL)
{
return this->real_stuff;
}
else
{
return default_stuff;
}

As others have mentioned, in C# you can do this with extension methods:

namespace Test
{
public class Widget
{
}
public static class WidgetExtensions
{
static public void Method(this Widget _this)
{
if (_this != null)
{
Console.WriteLine("real widget");
}
else
{
Console.WriteLine("null widget");
}
}
}
class Program
{
static void Main(string[] args)
{
Widget widget = null;

        widget.Method();
        
        widget = new Widget();
        
        widget.Method();
    }
}

}

results in the output

null widget
real widget

Software Zen: delete this;

[Jorgen Andersson]

That settles it for me, I want voting back. :thumbsup:

People say nothing is impossible, but I do nothing every day.

[Jorgen Andersson]

System.DBNull is an example of the pattern. And I can't describe in words how much I dislike it.

People say nothing is impossible, but I do nothing every day.

[Septimus Hedgehog]

So I was. Great minds think alike but in my case I'll pass up on the citation. ;) Hopefully it'll convince Muppet Maunder to read it and see if helps him.

"I do not have to forgive my enemies, I have had them all shot." — Ramón Maria Narváez (1800-68). "I don't need to shoot my enemies, I don't have any." - Me (2012).

[Chris Maunder]

I am humbled and ashamed. And have just found an endless opportunity for way, way more procrastination.

cheers, Chris Maunder The Code Project | Co-founder Microsoft C++ MVP

[Chris Maunder]

I respect a man who prefers power drills and small explosives where others would wimp out and use tweezers. :thumbsup:

cheers, Chris Maunder The Code Project | Co-founder Microsoft C++ MVP

[Chris Maunder]

Else? There is no else. Just blindly plow on!

cheers, Chris Maunder The Code Project | Co-founder Microsoft C++ MVP

[Pete OHanlon]

When I get the chance, I may just have a go at it. Need some free time first.

*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

[CodeHawkz]

The first code block doesn't make any sense to me but this line

var result = Test.NotNull(myObject).NotNull(myObject.MyProperty).IsPositive(myObject.MyProperty.Id);

can be represented like this, can't you?

var result = (myObject == null ? false: myObject.MyProperty == null ? false : IsPositive(myObject.MyProperty.Id);

Just bouncing off an idea :) P.S. You can do it much simpler by using exceptions, I believe Cheers

[NormDroid]

Aye :thumbsup:

Software Kinetics - Dependable Software news

[englebart]

Would the C# ?? operator help you?
Would that do what you want? It definitely saves typing.
http://msdn.microsoft.com/en-us/library/ms173224.aspx