Console.WriteLine()与Console.WriteLine(string.Empty)

Question

在我们的一个应用程序中,我遇到过这样的一些行:

Console.WriteLine(string.Empty);

如果我写的话,我检查了它是否有任何区别:

Console.WriteLine();

但输出是相同的(如预期的那样).

这个例子中的"最佳实践"是什么？是否有必要传递空string而不是传递任何参数的情况？

Answer 1

WriteLine() 像这样实现:

public virtual void WriteLine() {
    Write(CoreNewLine);
}

WriteLine(string) 但实现方式如下:

public virtual void WriteLine(String value) {
    if (value==null) {
        WriteLine();
    }
    else {
        // We'd ideally like WriteLine to be atomic, in that one call
        // to WriteLine equals one call to the OS (ie, so writing to 
        // console while simultaneously calling printf will guarantee we
        // write out a string and new line chars, without any interference).
        // Additionally, we need to call ToCharArray on Strings anyways,
        // so allocating a char[] here isn't any worse than what we were
        // doing anyways.  We do reduce the number of calls to the 
        // backing store this way, potentially.
        int vLen = value.Length;
        int nlLen = CoreNewLine.Length;
        char[] chars = new char[vLen+nlLen];
        value.CopyTo(0, chars, 0, vLen);
        // CoreNewLine will almost always be 2 chars, and possibly 1.
        if (nlLen == 2) {
            chars[vLen] = CoreNewLine[0];
            chars[vLen+1] = CoreNewLine[1];
        }
        else if (nlLen == 1)
            chars[vLen] = CoreNewLine[0];
        else
            Buffer.InternalBlockCopy(CoreNewLine, 0, chars, vLen * 2, nlLen * 2);
        Write(chars, 0, vLen + nlLen);
    }
}

如果用null字符串调用它,那么你得到的结果与WriteLine()没有参数的结果相同(加上一个额外的方法调用).但是,传递非空字符串时的逻辑有点复杂.

为此,string.Empty将分配一个长度为2的新字符数组,并将新行字符复制到该数组.

这通常不贵,但如果你不想打印任何东西,仍然有点多余.特别是对于固定电话Console.WriteLine来说,通过它没有任何意义string.Empty.

你应该更喜欢Console.WriteLine()过Console.WriteLine(string.Empty),如果单独为简单起见.