C# If item is not in array

Question

I have an array with these 3 items:

string[] departmentArray = {
    "Warranty Service Representative",
    "Warranty Service Administrative Manager",
    "Warranty and Site Administrator"
};

and I have this string

var department = "Warranty Service Representative"

I have this condition that is suppose to test if the string department is not in the departmentArray

if (Array.Exists(departmentArray, element => element != department)){
}

Clearly the string is in the array, so it should return false, but this returns true for my string. What Am I doing wrong?

On top of the answers below, Any() may work.

Drew Kennedy
– Drew Kennedy

2016-01-26 20:40:44 +00:00
Commented Jan 26, 2016 at 20:40 — Drew Kennedy
– Drew Kennedy, Commented Jan 26, 2016 at 20:40

Steve Wellens · Accepted Answer · 2016-01-26 22:11:17Z

25

Wouldn't this be simpler?

string[] departmentArray = { 
    "Warranty Service Representative", 
    "Warranty Service Administrative Manager", 
    "Warranty and Site Administrator" };

String department = "Warranty Service Representative";

if (departmentArray.Contains(department) == false)
{
}

edited Jan 26, 2016 at 22:11

answered Jan 26, 2016 at 20:28

Steve Wellens

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7 Comments

user979331 Over a year ago

What assembly do I need to use Contains?

user979331 Over a year ago

I get this error Error 1 'System.Array' does not contain a definition for 'Contains' and no extension method 'Contains' accepting a first argument of type 'System.Array' could be found (are you missing a using directive or an assembly reference?)

Steve Wellens Over a year ago

You need to add using System.Linq; at the beginning of your program. (I'm surprised it isn't already there, it is a Linq Extension).

Hutch Over a year ago

The <string> after Contains could also be excluded, as the compiler can derive what it should be.

Robbie Smith Over a year ago

What about something for a Dictionary lookup?

|

Broots Waymb · Accepted Answer · 2016-01-26 20:55:39Z

12

if (!Array.Exists(departmentArray, element => element == department))
{
}

In this case, underlying logic looks like:

!(departmentArray[0] == department || departmentArray[1] == department || ..)

While in your code, you have:

departmentArray[0] != department || departmentArray[1] != department || ..

edited Jan 26, 2016 at 20:55

Broots Waymb

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answered Jan 26, 2016 at 20:14

serhiyb

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4 Comments

user979331 Over a year ago

This will not work because in some cases I will have an array with 1 item and the string will match the one item in the array and will return true when I want that to return false

Steve Wellens Over a year ago

@user979331 Are you sure it will not work? Did you try it?

serhiyb Over a year ago

You might be confused by the expanded logic in the second part of my answer. Just try if (!Array.Exists(departmentArray, element => element == department)) instead of if (Array.Exists(departmentArray, element => element != department))

Aaron Over a year ago

To try to explain it in "human speak," your code is saying "If any of the elements of the array do not equal the department..." This answer is looking for an element equal to department. The expression will return true if any are equal, or false if none are. By moving the ! to the beginning, it's saying "If none of the elements equal department," which is your expected result.

leobelizquierdo · Accepted Answer · 2016-01-26 21:20:46Z

2

the code:

if (Array.Exists(departmentArray, element => element != department))
{
}

is true if exists any element in departmentArray != of department, that is why in this case the result is true instead of false (obviously there is strings in departmentArray different to department). So, if you want to check if department isn't in departmentArray try something like this:

bool IsNotInArray(String[] array, string element){
    return !Array.Exists(array, e => e == element);
}

answered Jan 26, 2016 at 21:20

leobelizquierdo

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