Null and blank values

Question

What's the best way of writing robust code so that a variable can be checked for null and blank.

e.g.

string a;

if((a != null) && (a.Length() > 0))
{
    //do some thing with a
}

Where did you hear of C#.Net? There is no such thing. – John Saunders May 25 '10 at 09:01 — John Saunders, May 25 '10 at 09:01

C.Evenhuis · Accepted Answer · 2011-12-06T09:19:53.457

7

For strings, there is

if (String.IsNullOrEmpty(a))

edited Dec 06 '11 at 09:19

answered May 25 '10 at 08:59

C.Evenhuis

25,996
2
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2

Better use String.IsNullOrEmpty() – HasanG May 25 '10 at 09:30
`string` beats `String` because you don't have to press shift, making your keyboard last longer, and makes you less tired, plus you don't need a `using System;` for the lowercase version. (kidding, applied and +1 for the correct capitalization when clearly accessing a static class method) – C.Evenhuis Dec 06 '11 at 09:19

score 3 · Answer 2 · answered May 25 '10 at 09:03

3

You can define an extension method to allow you to do this on many things:

static public bool IsNullOrEmpty<T>(this IEnumerable <T>input)
{
    return input == null || input.Count() == 0;
}

It already exists as a static method on the System.String class for strings, as has been pointed out.

answered May 25 '10 at 09:03

David M

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quoting John Skeet: However, you should definitely use Any(). That way it only needs to test for the presence of the first element. This will be incredibly cheap for normal implementations of ICollection, but could be *much* faster than Count() for cases involving a complex query. http://danielvaughan.orpius.com/post/IEnumerable-IsNullOrEmpty.aspx – Janko R May 25 '10 at 10:01

score 3 · Answer 3 · answered May 25 '10 at 09:04

3

And if you are using .NET 4.0 you might want to take a look at String.IsNullOrWhiteSpace.

answered May 25 '10 at 09:04

Anemoia

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score 1 · Answer 4 · answered May 25 '10 at 09:00

1

From version 2.0 you can use IsNullOrEmpty.

string a;
...
if (string.IsNullOrEmpty(a)) ...

answered May 25 '10 at 09:00

Patko

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Sander · Answer 5 · 2010-05-25T09:08:51.397

for strings:

string a;
if(!String.IsNullOrEmpty(a))
{
//do something with a
}

for specific types you could create an extention method note that i've used HasValue instead of IsNullorEmpty because 99% of the times you will have to use the !-operator if you use IsNullOrEmpty which I find quite unreadable

public static bool HasValue(this MyType value)
{
//do some testing to see if your specific type is considered filled
}

score 0 · Answer 6 · answered May 25 '10 at 09:08

0

if(string.IsNullOrEmpty(string name))
{
   ///  write ur code
}

answered May 25 '10 at 09:08

Johnny

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score 0 · Answer 7 · answered May 25 '10 at 09:53

I find Apache Commons.Lang StringUtils (Java)'s naming a lot easier: isEmpty() checks for null or empty string, isBlank() checks for null, empty string, or whitespace-only. isNullOrEmpty might be more descriptive, but empty and null is, in most cases you use it, the same thing.

Null and blank values

7 Answers7