C?操作员

Eric Lippert's Cast operators do not obey the distributive law

string.Format

(_Obj == null) ? "unknown" : _Obj.Id

int string ToString object

(_Obj == null) ? "unknown" : (object)_Obj.Id

int 到 对象 .

此表达式计算的类型是什么?

(_Obj == null) ? "unknown" : _Obj.Id

Conditional Operator

"the id is {0}", (_Obj == null) ? "unknown" : _Obj.Id

string integer

string text = string.Format("the id is {0}", _Obj.Id)

string.Format object

string.format (string, object)

? :

// WORKS, without implicit conversion 
string text = string.Format( 
    "the id is {0}", _Obj.Id); 

// NO WAY 
string text = string.Format( 
    "the id is {0}", (_Obj == null) ? "unknown" : _Obj.Id); 

(_Obj == null) ? "unknown" : _Obj.Id);

function int Eval(object obj)
{
  if (obj == null)
  {
    return "unknown";
  }
  else
  {
    return "1";
  }
}

string.format

_Obj == null string int string text