What is the most common error in a .Net application?

[leppie]

This is the most common error for most languages that support null/NULL reference assignment.

xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 beta 1 - out now!
((lambda (x) `((lambda (x) ,x) ',x)) '`((lambda (x) ,x) ',x))

[Super Lloyd]

And what about Trim()? Hehe... Just want to point out that the very limited scope of your warning is funny! ;P Any method can potentially fire a null reference exception hey! :-D

A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

[ToddHileHoffer]

In .net it is the classic "object reference not set to an instance of an object". Speaking of bugs, I started a new position back in June. This company (not an IT company) does an amazing job of testing. The first application I did here was coded in about 4 weeks by myself and a consultant. The company used the application in test for an entire month before we rolled it out. It has been live for six weeks now without one bug or code change required. This is the first time, I have accomplished this.

I didn't get any requirements for the signature

[jith iii]

If you can assign null to a string,why the hell they are not making null.ToString() atleast null without cribbing. I hate the concept of null considering the harm this error caused to our delivery.

[jith iii]

:) ...but I don't know, ToString() is quite popular here. It's coming repeatedly everywhere. May be,people Trim() only after they polish the null refernece with ToString()

[Tomz_KV]

That is something I do not understand. Why ToString() can't handle the "null" automatically? It must have a good reason.

TOMZ_KV

[Rob Graham]

jith - iii wrote:

If you can assign null to a string,

You're not assigning null to a string. You're setting a reference to a string to null (meaning it refers to nothing), not at all the same thing. You are forgetting that strings are reference types, not value types. Since the null is an invalid reference, there is nothing (no class instance or static object) which might implement ToString(), hence the null reference exception.

[Gary Wheeler]

My approach is to strike first.

Software Zen: delete this;

[Rob Graham]

It's similar to an uninitialized pointer in C++. It's just the address of an object (which if null is an invalid address), nothing exists to implement the method.

[PJ Arends]

Quick! Knock on wood. Now that you mentioned it out in the open, the bug reports will come swarming in.

---

You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!

[Rama Krishna Vavilala]

You should program in Objective C where it is legal to invoke methods on nulls.

id v = nil;
NSString* valueAsString = [v description];

modified on Monday, December 15, 2008 2:58 PM

[Rob Graham]

Would his code have been any less broken?

[Super Lloyd]

ObjectiveC is a beast of its own... It's even legal to call method which don't exist! Who knows, a Forward or a Category might even intercept them?

A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station.... _________________________________________________________ My programs never have bugs, they just develop random features.

[Rama Krishna Vavilala]

It Depends:).

[Rama Krishna Vavilala]

Super Lloyd wrote:

It's even legal to call method which don't exist!

Yes and this feature has its own strengths (and weaknesses).

[TheGreatAndPowerfulOz]

in C++, the target function actually gets called and so long as no reference is made to instance variables in that function, no null reference will occur due to the null 'this' (obviously, something else could be null). So, a somewhat common tactic is to test for "this == null" or "this != null".

[TheGreatAndPowerfulOz]

add a static extension method

string string.ToString(string target)
{
return (target ?? "").ToString();
}

or simply code your ToString calls as:

(target ?? "").ToString()

[dan sh]

334,000 google search results for the error message(with quotes). It surely is the most popular

C isn't that hard: void (*(*f[])())() defines f as an array of unspecified size, of pointers to functions that return pointers to functions that return void "Always program as if the person who will be maintaining your program is a violent psychopath that knows where you live." - Martin Golding

[jith iii]

well,grammer may be wrong,but I meant the same. It will instantly give error if you try to set null to an integer,right? why double standard to string where you can set it to nothing but not otherwise? :) (Just consider this as an emotional outburst. I don't really want to excuse people forgetting a null check)

[Tomz_KV]

I've been using (target==null?"":target).ToString( :) ) so far. ?? is a nicer.

TOMZ_KV