How To Insert A UTF-8 Encoding Type Character Into A Sql Server Text DataType Field ?

I want to insert a value which has the UTF-8 encoding into a field of the database which has the "text" data Type
but it saves like this : " ?????????????? "

I would be thankful if u tell me how should I save it ?
here is the SqlComand I wrote :

string comand = " Insert into Table1 ( title , Body ) values ( ' " + textBox1.text + " ' , ' " + textBox2.text + " ' ) " ;


Table1
=============
title nvarchar(1000)
body text