Best way to check if a string is empty

Hi all,

I am just wondering how you all check if a string is empty in C#.
I am a C/C++ programmer, and I usually check if the string is empty with the following code.

Code:

---

if( strString.length() == 0 || strString.compare( "" ) == 0 )
    // string is empty
else
    // do something useful with the string

---

so naturally, I am checking if a string is empty with the following code in c#

Code:

---

if( strString.length == 0 || strString.CompareTo( "" ) == 0 )
  // string is empty

---

Is there a better way to check if a string is empty in C#?
Thank you,
kab

Code:

---

if(String.IsNullOrEmpty(str))
{
//...
}

---

Assuming you do not need to differentiate between null and empty :D:D

If you want to check specifically for empty...

Code:

---

if (stringVar != String.Empty)
{
  //  It is NOT empty...however it might be Null.....
}

---

Ahh, I guess both functions are helpful, but I think IsNullOrEmpty is better for me =)
Thanks to both.

Hmm, TheCPUWizard, I can't give you another reputation. It seems like I have to wait for longer..

Quote:

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Originally Posted by kabilius

Code:

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if( strString.length() == 0 || strString.compare( "" ) == 0 )

---

---

In what language would an empty string *not* compare with "" to give the value of '0'. Isn't that a redundant statement no matter what language you're in?

Quote:

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Originally Posted by Mutant_Fruit

In what language would an empty string *not* compare with "" to give the value of '0'. Isn't that a redundant statement no matter what language you're in?

---

Hi Mutant_Fruit,

Are you saying strString.length() == 0 is equivalent to strString.compare( "" ) == 0?
Yeah, now that I take a closer look, I think they are equivalent....
I don't remember why I put these two statements together, maybe it was just a way to make me feel that I am performing plentful sanity checks.....

kab

Quote:

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Originally Posted by kabilius

maybe it was just a way to make me feel that I am performing plentful sanity checks.....

---

Sanity checks are great, but only if they add value. In this case, it's redundant.

Quote:

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Originally Posted by Arjay

Sanity checks are great, but only if they add value. In this case, it's redundant.

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Yes sir, I understand. I was trying to find a way out to explain why I have this redundant statement, and making me feel safer about my code was the best reason I found.... =p

Thanks for the input, I will try not to write statements like this in the future
kab

I do it like this, I added the Trim method just to eliminate spaces.

Code:

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if (strString.Trim().Length == 0)

---

that's just one of those things that would get noticed and discussed during a code review. and why code reviews are such a worth while endeavor.

Quote:

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Originally Posted by dee-u

I do it like this, I added the Trim method just to eliminate spaces.

Code:

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if (strString.Trim().Length == 0)

---

---

I would not recommend doing that in any code that someone else has to modify. For one, it is inefficient (you are calling two methods instead of comparing against a static value), two, it is not clear why you would do that, and three, it is incorrect. however unlikely it may be, a string containing only spaces is not an empty string. You are not checking the value of the original string, you are creating a new string and checking its value.

Quote:

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Originally Posted by BigEd781

I would not recommend doing that in any code that someone else has to modify. For one, it is inefficient (you are calling two methods instead of comparing against a static value), two, it is not clear why you would do that, and three, it is incorrect. however unlikely it may be, a string containing only spaces is not an empty string. You are not checking the value of the original string, you are creating a new string and checking its value.

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Agreed. I try to avoid situations where extra leading or trailing spaces are added or when they are added, they're a necessary part of the string.

If I don't need the spaces, I'll trim them before I store them into the string.

That way any subsequent checks are reduced to

Code:

---

if( !String.IsNullOrEmpty( str ) )
{
  //...
}

---

Quote:

---

Originally Posted by BigEd781

I would not recommend doing that in any code that someone else has to modify. For one, it is inefficient (you are calling two methods instead of comparing against a static value), two, it is not clear why you would do that, and three, it is incorrect. however unlikely it may be, a string containing only spaces is not an empty string. You are not checking the value of the original string, you are creating a new string and checking its value.

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Not only that, it will CRASH on a null string. :eek::eek:

TOTALLY DEFEATING the original purpose!

I'm glad to learn something which I was not aware of. Thanks guys!

Edit:
Actually, the primary reason I am using that is I am using this VB6.0 code to determine the 'emptiness' of a string and this is the most officient method I have known so far.

Code:

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If Len(Trim$(x)) = 0 Then

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All I thought it would convert to the .Net code I posted earlier.

Sorry for hijacking this thread but I just need a little more clarification.

For instance I have a Textbox that is used to input a Last Name that goes to a specific field in a table. A user pressed the Space key in the keyboard for that Textbox. If I need to store in a string the value of that textbox then how should I proceed?