initialised string seems to contain string.Empty

Question

I jumped into this accidentally and have no clue as to why this is happening

string sample = "Hello World";
if (sample.Contains(string.Empty))
{
    Console.WriteLine("This contains an empty part ? at position " + sample.IndexOf(string.Empty));
    Console.WriteLine(sample.LastIndexOf(string.Empty));
    Console.WriteLine(sample.Length);
}

Output

This contains an empty part ? at position 0

10

11

I am happy with the last part, but i have no idea why this is evaluated true. Even Indexof and LastIndexOf have separate values.

Could anyone help me out on why is this so?

EDIT

I believe this is a bit relevant to my question and would be also helpful to those who stumble upon this question.

See this SO link: Why does "abcd".StartsWith("") return true?

score 16 · Accepted Answer · answered May 04 '11 at 11:48

16

From msdn for IndexOf

If value is String.Empty, the return value is 0.

For LastIndexOf

If value is String.Empty, the return value is the last index position in this instance.

For Contains

true if the value parameter occurs within this string, or if value is the empty string ("");

answered May 04 '11 at 11:48

SwDevMan81

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@SwDevMan81: shouldn't that be 11 instead of 10 ? – V4Vendetta May 04 '11 at 11:50
@V4Vendetta - last index is 10 (0 to 10 is 11 characters) – SwDevMan81 May 04 '11 at 11:51
@SwDevMan81: sorry my mistake didn't read `index`, So does it imply that for any string as given above string.Empty will always resolve to true (would be glad to know if there is an exceptional case) – V4Vendetta May 04 '11 at 11:56
@V4Vendetta - Yup, it will always return true if the input is String.Empty – SwDevMan81 May 04 '11 at 11:57
@SwDevMan81: well i was looking more on `why` does it do so – V4Vendetta May 04 '11 at 12:00
@SwDevMan81: Found something similar on SO.. Jason has interesting explanation ..thanks for helping me out. – V4Vendetta May 09 '11 at 09:39

RB. · Answer 2 · 2011-05-04T11:53:36.013

4

Question: Does the string "Hello World" contain String.Empty?

Answer: Yes.

Every possible string contains String.Empty, so your test is correctly returning true.

If you are trying to test if your string is empty, then the following code is what you want

if (string.IsNullOrEmpty(sample)) 
{

}

edited May 04 '11 at 11:53

answered May 04 '11 at 11:47

RB.

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score 1 · Answer 3 · answered May 04 '11 at 11:49

This is documented in the String.Contains Method:

Return Value
Type: System.Boolean
true if the value parameter occurs within this string, or if value is the empty string (""); otherwise, false.

And in String.IndexOf Method

If value is String.Empty, the return value is 0.

And in LastIndexOf Method

If value is String.Empty, the return value is the last index position in this instance.

initialised string seems to contain string.Empty

3 Answers3