Connecting S71200 Siemens PLC to c#

Im writing bool data to siemens PLC S71200 from C#. but im getting last error String Like "Wrong NumberReceived Bytes" and Last Error code is "Write Data". Y this Error is getting while excecuting function

 

 

here my code

bool Writetoplc=true;

_s71200.Write("DB15.DBX12.1",Writetoplc); 

 

For this perticular code only getting above mentioned error .