I'm sure I've missed something here. With a certain project I need to check if a string is null or empty.
Is there an easier way of writing this?
if (myString == null || myString == "") { ... 
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7 Answers
Yes, there's the String.IsNullOrEmpty helper method for exactly this already:
if (String.IsNullOrEmpty(myString)) { ... } 
4 Comments
xanatos
And on a relate note: stackoverflow.com/questions/2552350/…
kayleeFrye_onDeck
Just to be super-clear, you need to use the class function for
string/String, NOT trying to use the function via the object! Eg, String foo; will not allow you to do foo.IsNullOrEmpty();; you need to use it like String.IsNullOrEmpty(foo); This is kind of annoying when coming from other languages that have built in null/0-length-checks for their string objects, since you can't safely do something like, if(foo.Length == 0) because that can trigger an exception.
Joey
@kayleeFrye_onDeck: You should be able to use
if (foo?.Length ?? 0 == 0), but in general, calling an instance method requires a non-null reference. You can fake this with extension methods that don't check their argument, but I think that's frowned upon, as extension methods should behave as if they were instance methods.kayleeFrye_onDeck
That's some strange syntax o_o I'm not a C# developer, just someone who happens to use it once in a while to develop modules with it ad-hoc but I can't say I've seen anything like that before... I get what it's doing, just wished I knew about it sooner!
if (string.IsNullOrEmpty(myString)) { ... } Or you could take advantage of a quirk in extension methods, they allow this to be null:
static class Extensions { public static bool IsEmpty(this string s) { return string.IsNullOrEmpty(s); } } which then lets you write:
if (myString.IsEmpty()) { ... } Although you probably should pick another name than 'empty'.
2 Comments
Phil
Nice example of extension methods! Thanks!
Sarfaraz Nawaz
Why not
string.IsNullOrEmpty(s) instead of s == null || s == string.Empty?If you are on .NET 4, you can use
if(string.IsNullOrWhiteSpace(myString)){ } else:
if(string.IsNullOrEmpty(myString)){ } 
1 Comment
Joey
IsNullOrWhiteSpace checks for something else than being equal to "" so it'd have different semantics than the code snippet in the question.To avoid null checks you can use ?? operator.
var result = value ?? ""; I often use it as guards to avoid sending in data that I don't want in methods.
JoinStrings(value1 ?? "", value2 ?? "") It can also be used to avoid unwanted formatting.
string ToString() { return "[" + (value1 ?? 0.0) + ", " + (value2 ?? 0.0) + "]"; } This can also be used in if statements, it's not so nice but can be handy sometimes.
if (value ?? "" != "") // Not the best example. { } 
1 Comment
Israfel
?? can be used to avoid null check but not for "". "" ?? anything" still yeilds to ""In c# 9 by using pattern matching you could do the following
myString is not {Length: > 0}; // Equivalent to string.IsNullOrEmpty(myString) 
2 Comments
Caius Jard
Honestly? I don't like it.. "myString is not an object with a length property that is greater than zero" - this is a negative flavored test (like a test for success being
if(!operationFailed) - negative flavored / if(operationSucceeded) - positive flavor). You have to stop and think about what it actually means/what the author intended so it reduces code readability/glanceability/self-documentation. IsNullOrEmpty does a really good job of explaining what it does.
Boris Lipschitz
It might be not so great for readability but it's a feature of the language now
C# 9's pattern matching allows you to write:
myString is null or "" Comments
// if the string is not defined to null then IsNullOrEmpty it works great but if string is defined null then trim will throw exception.
if(string.IsNullOrEmpty(myString.Trim()){ ... } //you can use IsNullOrWhiteSpace which work well for multiple white space in string .i.e it return true for multiple white space also
if(string.IsNullOrWhiteSpace (myString.Trim()){ ... } 
2 Comments
Hans Kesting
"Trim" is not a standalone function, it is an instance method of String. Proper usage:
myString.Trim(), but that blows up when mystring is null. Use String.IsNullOrWhiteSpace()
Dipitak
i agree with you, so i have corrected in above code. Thanks @HansKesting