c# – 字符串数组加字符串不是错误,为什么？

来自C#Spec $7.8.4 Addition operator

string operator + (string x,string y);
string operator + (string x,object y);
string operator + (object x,string y);

这就是你的var a =(new string [] {})string.Empty;匹配第三个重载.

并且(对象x,字符串y)使用String.Concat(object,object)重载,这是implemented之类的;

public static String Concat(Object arg0,Object arg1)
{ 
     if (arg0 == null)
     {
         arg0 = String.Empty;
     }

     if (arg1==null) {
         arg1 = String.Empty;
     }
     return Concat(arg0.ToString(),arg1.ToString());
}

因为新的string [] {}不是null,因为在MSIL中,它使用newarr及其文档;

The stack transitional behavior,in sequential order,is:

1. The number of elements in the array is pushed onto the stack.
2. The number of elements is popped from the stack and the array is created.
3. An object reference to the new array is pushed onto the stack.

这就是它最后使用object.ToString()方法的原因.

从它的文件;

ToString is the major formatting method in the .NET Framework. It
converts an object to its string representation so that it is suitable
for display.The default implementation of the ToString method returns the fully
qualified name of the type

结果你的a将是System.String [].