Lambda expression Any returns wrong value

Question

I have this lambda expression:

if (!myList.Any( x => x.name == "example" && x.articleNumber == "1"))
{

}
else
{

}

myList contains an object from the class which has these properties: articleNumber, name and quantity.

And this enters in the if instead of in the else althought there is an object with name "example" AND articleNumber "1". Why does this happen?

if you don't have an entry with name example and acticleNumber 1 it should go into the if block. — Øyvind Bråthen
– Øyvind Bråthen, Commented Jan 4, 2013 at 9:28
Because no elements of myList match the predicate? If you think something should match, I'd check again. (The debugger will be your friend here and you can iterate through the list if you'd like) — lc.
– lc., Commented Jan 4, 2013 at 9:28
What is in the list and what is your expected result? We can't tell you why without the scope. — LukeHennerley
– LukeHennerley, Commented Jan 4, 2013 at 9:29

Vishal Suthar · Accepted Answer · 2013-01-04 09:34:58Z

4

You are aware of the ! before your lamda right?

what you are asking in the if statement is

If myList does NOT contain any values where name is example AND article number is 1

I don't know if this helps but maybe it's easier to answer if you supply more information about what you want to accomplish with the statement.

edited Jan 4, 2013 at 9:34

Vishal Suthar

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answered Jan 4, 2013 at 9:30

Moriya

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Comments

Tim Schmelter · Accepted Answer · 2013-01-04 09:37:21Z

1

The only reason i can see is that there's no element with name=="example" and articleNumber=="1". Note that the == operator is case sensitive in C# and that there might be a white-space somewhere.

Then you can use this overload of Equals to compare case-insensitive and remove white-spaces with Trim:

if (!myList.Any( x => x.name.Trim().Equals("example", StringComparison.OrdinalIgnoreCase) 
                   && x.articleNumber == "1"))
{

}
else
{

}

You should also consider to change the type of articleNumber to int since it is a number.

edited Jan 4, 2013 at 9:37

answered Jan 4, 2013 at 9:31

Tim Schmelter

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Comments

Øyvind Bråthen · Accepted Answer · 2013-01-04 09:30:38Z

1

I'm pretty sure that the list don't contain the entry you think it does. Set a debug marker on the if line, and inspect the list at that point to see what it contains. You will find that the entry is not there. Remember that strings are case sensitive as well, so if name really is Example, it will not match.

answered Jan 4, 2013 at 9:30

Øyvind Bråthen

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3 Comments

Øyvind Bråthen Over a year ago

It does not contain exactly that at least. Im sure that Any is not broken in suck a way.

Øyvind Bråthen Over a year ago

So the most likely cancidates for it looks the same is a problem with case in the text "example", or some whitespace somewhere in one of the two strings.

Øyvind Bråthen Over a year ago

If you still believe it contains the correct value, take a screenshot of the inspected list when debugging at the if statement, and post it to your question.

CR41G14 · Accepted Answer · 2013-01-04 09:30:45Z

1

Nothing wrong with your logic but you counld try??

if (myList.Where( x => x.name == "example").Where(x=> x.articleNumber == "1").Count() > 0)
{

}
else
{

}

OR to remove all spaces and variances in Casing

if (!myList.Any( x => x.name.Trim().ToLower() == "example" && x.articleNumber.Trim().ToLower() == "1"))
{

}
else
{

}

answered Jan 4, 2013 at 9:30

CR41G14

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2 Comments

Øyvind Bråthen Over a year ago

Why would you complicate the if statement to produce the exact same result?

jp2code Mar 20 at 16:13

@ØyvindBråthen - he added a .Trim() and a .ToLower() to eliminate cases such as "Example", "example ", etc.

Konstantin Spirin · Accepted Answer · 2013-01-04 10:08:08Z

1

Your list probably contains some values that you don't expect.

Try to replace && with || and see what you will get:

var v = myList.Where(x => x.name == "example" || x.articleNumber == "1").ToList();

just to see what's there .

answered Jan 4, 2013 at 10:08

Konstantin Spirin

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Comments

Johannes Wanzek · Accepted Answer · 2013-01-04 09:36:55Z

0

The definition of Any: Determines whether any element of a sequence exists or satisfies a condition.

So for each element in a sequence it is determined if the predicate is matching your expression.

myList.Any( x => x.name == "example" && x.articleNumber == "1")

Will return true if ANY element of the List has the name "example" AND the articleNumber 1.

!myList.Any( x => x.name == "example" && x.articleNumber == "1")

Will return true if NO element of the List has the name "example" AND the articleNumber 1.

answered Jan 4, 2013 at 9:36

Johannes Wanzek

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