Linq select Objects from List which have empty String

Question

is it possible in Linq to select from IEnumerable of this object

public class Foo
{
    public int Id { get; set; }
    public string Type { get; set; }
}

where Type is "" ?

if I loop over the list with that

        foreach (Foo f in dataFoos)
        {
            Console.WriteLine(f.Id + f.Type);
        }

it looks like

1one

2

3three

I have tried

var emptyType0 = dataFoos.Where(f => f.Type.Length <= 1);
var emptyType1 = dataFoos.Where(f => f.Type == null || f.Type == "");

both did not return any result. Any hint on how to properly check if String values are empty ?

if I do that

        var df = dataFoos.Where(f => String.IsNullOrWhiteSpace(f.Type));

        foreach (Foo f in df)
        {
            Console.WriteLine(f.Id + f.Type);
        }
        var df1 = dataFoos.Where(f => !String.IsNullOrWhiteSpace(f.Type));

        foreach (Foo f in df1)
        {
            Console.WriteLine(f.Id + f.Type);
        }

the second loop does not return any value

I am using dotnetcore c#. Thanks for any hint

Your code should work. Show how you populate your foos variable. — SomeBody
– SomeBody, Commented Jan 7, 2021 at 11:33
I have added some loop output. Still the linq queries are empty — user3732793
– user3732793, Commented Jan 7, 2021 at 11:42
If any object have f.Type = null then your first Where(f => f.Type.Length <= 1) will throw exception. Moreover it should be < 1 not <= 1. Your second condition is perfect but what if your Type has value with spaces (" ") then it will not return those. You can use var emptyType1 = foos.Where(f => string.IsNullOrWhiteSpace(f.Type)); or use Trim() as var emptyType1 = foos.Where(f => f.Type == null || f.Type.Trim() == ""); — Karan
– Karan, Commented Jan 7, 2021 at 11:42
@user3732793: Are you sure that your second entry is acutally empty? Or does it have some whitespace character like space or tab? — SomeBody
– SomeBody, Commented Jan 7, 2021 at 11:45

Jamiec · Accepted Answer · 2021-01-07 11:45:31Z

3

This should cover almost every type of null/blank/just whitespace

var emptyType1 = foos.Where(f => String.IsNullOrWhiteSpace(f.Type));

but more likely what you want to do is exclude those - not include them

var dataFoos = foos.Where(f => !String.IsNullOrWhiteSpace(f.Type));

foreach (Foo f in dataFoos)
{
    Console.WriteLine(f.Id + f.Type);
}

answered Jan 7, 2021 at 11:45

Jamiec

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11 Comments

Magnetron Over a year ago

Side note: Any styling reason why you use String instead of string?

Jamiec Over a year ago

@Magnetron it's the same thing. One is just an alias of the other

user3732793 Over a year ago

@Jamiec that did work but than foos is empty I would hope I can generate other Lists too from foo !?

Jamiec Over a year ago

@user3732793 I'm afraid I don't understand. What other list do you want to generate?

Jamiec Over a year ago

@Magnetron habit only I guess. string is the c# type so I use that for defining params/vars etc. String has static methods like IsNullOr..... I know you can use either interchangably but it's just my personal taste

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