What is the most optimal method of checking if a string is empty?

Question

To check whether a string is empty I use

var test = string.Empty; 
if (test.Length == 0) Console.WriteLine("String is empty!");
if (!(test.Any())) Console.WriteLine("String is empty!");
if (test.Count() == 0) Console.WriteLine("String is empty!");
if (String.IsNullOrWhiteSpace(test)) Console.WriteLine("String is empty!");

All the above statements produces the same output. What is the optimal method that I should use?
```
var s = Convert.ToString(test);    
s = test.ToString(CultureInfo.InvariantCulture);
```
Again, both statements does the same thing. What is the best method to use?

I tried debugging and how to benchmark the performance of a C# statement?

detailed explanation here: http://stackoverflow.com/questions/305092/which-method-performs-better-any-vs-count-0 — Mike Trusov, Nov 07 '12 at 09:13
thanks.. but could some one say how to measure the performance/benchmark .any or .length c# ? — now he who must not be named., Nov 07 '12 at 09:16
Simplest profiling approach is using Stopwatch class provided by Diagnostics. You start it, execute code 1000 times, stop it, see how long it took. Wrap that in another for loop for better average. Then sub in other code to compare. — Mike Trusov, Nov 07 '12 at 09:19
In (1) since apparently you don't care about white spaces, why don't you just check with `test == ""` or `test == string.Empty`? — Paolo Moretti, Nov 07 '12 at 09:25
Yes @PaoloMoretti: If in this case, I think I should have been trimmed the string by test.Trim().Length should have been done. — now he who must not be named., Nov 07 '12 at 09:27
And one more: If string is null, then Convert.ToString just returns null but string.ToSTring() throws a exception. — now he who must not be named., Nov 07 '12 at 09:37

Peter · Accepted Answer · 2012-11-07T09:25:40.787

First of all the 4 statemens are not giving the same output on all inputs. Try null and the first 3 will throw an exception. And try whithspaces the last one will give you a failty result. So you really have to think about what you want. The best way to go are normally the:

string.IsNullOrEmpty
string.IsNullOrWhiteSpace

Only if you are doing this a few million times you should have a look on how to optimize your code further.

Here some test result, but this can differ on any .net version:

Test results for 100 million iterations:

Equality operator ==:   796 ms 
string.Equals:          811 ms 
string.IsNullOrEmpty:   312 ms 
Length:                 140 ms  [fastest]
Instance Equals:       1077 ms

source

codingbiz · Answer 2 · 2012-11-07T09:38:25.027

3

I would go for String.IsNullOrWhiteSpace or String.IsNullOrEmpty.

Length, Count and Any could fail if test is null with object null reference]

Update

Unless you are sure your string won't be null, then you will have to check if string is null before testing the length or count or calling any method on the variable.

In these scenario, .Length is not the same as String.IsNullOrWhiteSpace

string test = "    ";
test.Length == 0;  //false
String.IsNullOrWhiteSpace(test); //true

edited Nov 07 '12 at 09:38

answered Nov 07 '12 at 09:18

codingbiz

26,179
8
59
96

That means, an exception will be thrown if the string is null. So to avoid exception handling, it is better to go with IsNullorWhiteSpace ? – now he who must not be named. Nov 07 '12 at 09:25
Unless you are sure `test` must have a value, `String.IsNullOrEmpty` is safer – codingbiz Nov 07 '12 at 09:27
But, IsNullorWhiteSpace checks for null, whitespace and empty string, should it be better If I use it instead of IsNullorEmpty ? – now he who must not be named. Nov 07 '12 at 09:28
that would depend on your application. Tab and Enter are not possible in a single line textbox. If you pressed tab, it would go to the next control, if you pressed enter, it would submit the form or do nothing. If you don't want use to press spacebar as valid input, you would use `IsNullorWhiteSpace` which can also achieve with `Trim()`. That depends on which is convenience. If spaces are allowed, `IsNullOrEmpty` is enough – codingbiz Nov 07 '12 at 09:35

score 1 · Answer 3 · answered Nov 07 '12 at 09:12

As far as I'm aware:

.Any(): has the intent of checking whether any objects exist in an array. And since string is an array of char, this works. And is part of Linq

.Length: has the intent of giving you the length of the array of char.

So, yes the same behavior, but slightly different intents.

BTW, you should really use String.IsNullOrWhitespace to check strings as empty. At least that is my preference so that if you have a string of many whitespace characters you don't have to trim first.

+1 for "string is an array of char, this works. And is part of Linq" — now he who must not be named., Nov 07 '12 at 09:30

score 1 · Answer 4 · answered Nov 07 '12 at 09:32

For one variable, results are:

String.IsNullOrEmpty(test) < String.IsNullOrWhiteSpace(test) << test.Length==0 <<< !(test.Any())≡test.Count() == 0
test.ToString(CultureInfo.InvariantCulture) < Convert.ToString(test) (Order of 10 times)

I used the following code snippet to test the above.

static void Main(string[] args)
    {
        var test = string.Empty;
        System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
        sw.Start();
        if (test.Length == 0)
        {
            sw.Stop();
            Console.WriteLine("String is empty!  " + sw.ElapsedTicks);
        }
        sw.Restart();
        if (!(test.Any()))
        {
            sw.Stop();
            Console.WriteLine("String is empty!  " + sw.ElapsedTicks);
        }
        sw.Restart();
        if (String.IsNullOrWhiteSpace(test))
        {
            sw.Stop();
            Console.WriteLine("String is empty!  " + sw.ElapsedTicks);
        }
        sw.Restart();
        if (String.IsNullOrEmpty(test))
        {
            sw.Stop();
            Console.WriteLine("String is empty!  " + sw.ElapsedTicks);
        }
        sw.Restart();
        if (test.Count() == 0)
        {
            sw.Stop();
            Console.WriteLine("String is empty!  " + sw.ElapsedTicks);
        }
        sw.Restart();
        var s = Convert.ToString(test);
        sw.Stop();
        Console.WriteLine("String is empty!  " + sw.ElapsedTicks);
        sw.Restart();
        s = test.ToString(CultureInfo.InvariantCulture);
        sw.Stop();
        Console.WriteLine("String is empty!  " + sw.ElapsedTicks);
        Console.ReadKey();
    }

Infact String.IsNullOrEmpty(test) is the best as pointed out by somebody in the comments above... :)

:But why not String.IsNullOrWhiteSpace() preferred over NullorEmpty — now he who must not be named., Nov 07 '12 at 09:38
Well, strictly going by performance, `String.IsNullOrEmpty()` serves your purpose. And yeah, a great question... :) — Viral Jain, Nov 07 '12 at 09:41

What is the most optimal method of checking if a string is empty?

4 Answers4

Update