C# - What does "\0" equate to?

I am playing with Pex and one of the parameters it passes into my method is "\0".

What does that mean? My guess is an empty string ("") based on the content of my method. However, if it is the same then why not just use "" instead of "\0"?

Anyone know what it is?

'\0' is a "null character". It's used to terminate strings in C and some portions of C++. Pex is doing a test to see how your code handles the null character, likely looking for the Poison Null Byte security exploit.

Most C# code has nothing to fear; if you pass your string to unmanaged code, however, you may have problems.

Edit:

Just to be explicit... Pex is passing a string containing a null character. This is not a null reference.

It's a string containing the character '\0'. C# doesn't treat this in any particularly special way - it's just unicode character U+0000. If you write:

int firstCodePoint = text[0];

then you'll find firstCodePoint is 0.

It's a string with a null character. Older string libraries — like that used in C or older C++ libraries — used the '\0' character to indicate the end of the string.

Newer environments like .Net use a different system, but there is a lot of history around ending a string with '\0', such that it's a common point of error. Testing libraries like Pex will use it to make sure your program handles it correctly.

Escape Sequence  
\0    
Character Name 
Null    
Unicode Encoding     
0x0000

See this link.

A string of length 1, containing the character \u0000 (aka NUL). This character is not treated specially.

In C, which uses \0 to terminate string, you also allocate a string of length 1. In this case the standard string functions will report a length of 0, since the string contains \0 as well as being terminated with it. You could safely modify str[0], or strncat a single character into it.