Consider the code below.
Public
interface  
IstringInterface
{              
String str {get;}
}
Public
class StringClass: 
IstringInterface
{               
//Implicit implementation 
Public
string str
{               Return 
“Implicit interface 
Implementation” ;
}
//explicit 
implemenatation
Public
string IstringInterface.str
{               Return 
“Explicit interface 
Implementation” ;
}
}
Main()
{ StringClass obj =
new StringClass();
//Implicit
Obj.str                   
// work fine   Calling way 1
(IstringInterface (Obj)).str
// works fine  calling way 2
//Explicit
Obj.str// not works  Calling way 1
(IstringInterface (Obj)).str
// // works fine  calling way 2
}
For the implicit implementation Calling way 1 and Calling way 2 works fine. But Here, 
from the yellow line, if we use the explicit implementation then we will not be able to 
call the method directly, and only the calling way 2 will work.