C# – Why is the default value of the string type null instead of an empty string

cdefault-valuestring

It's quite annoying to test all my strings for null before I can safely apply methods like ToUpper(), StartWith() etc…

If the default value of string were the empty string, I would not have to test, and I would feel it to be more consistent with the other value types like int or double for example.
Additionally Nullable<String> would make sense.

So why did the designers of C# choose to use null as the default value of strings?

Note: This relates to this question, but is more focused on the why instead of what to do with it.

Best Answer

Why is the default value of the string type null instead of an empty string?

Because string is a reference type and the default value for all reference types is null.

It's quite annoying to test all my strings for null before I can safely apply methods like ToUpper(), StartWith() etc...

That is consistent with the behaviour of reference types. Before invoking their instance members, one should put a check in place for a null reference.

If the default value of string were the empty string, I would not have to test, and I would feel it to be more consistent with the other value types like int or double for example.

Assigning the default value to a specific reference type other than null would make it inconsistent.

Additionally Nullable<String> would make sense.

Nullable<T> works with the value types. Of note is the fact that Nullable was not introduced on the original .NET platform so there would have been a lot of broken code had they changed that rule.(Courtesy @jcolebrand)

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