问题
According to both Intellisense and MSDN doc on string.Split, there are no parameterless overloads of string.Split. Yet if I type in
string[] foo = bar.Split();
It compiles. And it works. I have verified this in both Visual Studio 2008 and 2010. In both cases intellisense does not show the parameterless overload.
Is there a reason for this? Are there any other missing overloads from the MSDN/Intellisense docs? Usually browsing through overloads in intellisense is how I best determine which overload to use. I'd hate to think I am missing other available options throughout the .Net framework.
EDIT: as shown above, it splits on whitespace.
回答1:
That is because Split has a params overload. Giving no parameters is the same as giving an empty array. In other words, you are calling this overload.
"some text".Split();
Is the same as:
"some text".Split(new char[0]);
Here is the documentation on the params keyword. As you probably know, it is used for giving a method a variable number of parameters. That number may be zero.
回答2:
I bet it's matching this String.Split overload:
public string[] Split(params char[] separator)
{
return this.Split(separator, 0x7fffffff, StringSplitOptions.None);
}
0 arguments is acceptable for this function. Given no separators, it defaults to white space.
回答3:
Actually what you are calling here is string.Split(params char[] separator)
params (C# reference)
You can send a comma-separated list of arguments of the type specified in the parameter declaration, or an array of arguments of the specified type. You also can send no arguments.
回答4:
It has to do with a weakness of exposing parameters as 'params array[]'. See the signature of the following method as documented in MSDN, so obviously you are passing in an empty array.
public string[] Split(params char[] separator)
回答5:
String.Split() has a number of overloads; you are correct that none of those overloads is parameter-less, however, one of them is varadic: String.Split(params char[]). The variable length portion of the argument list can be any number of arguments, including zero -- that is the overload you're invoking here.
回答6:
public string[] Split(params char[] separator)
params is 0 or more
来源：https://stackoverflow.com/questions/2906621/undocumented-overload-of-string-split