How to insert unicode data in sql using c#

I am developing a windows application in which the input is in marathi language. I have the code to insert data in sql server.

create database Test

create table marathi(Names nvarchar(22))

insert marathi SELECT N'???????'     ---- Right Query

insert marathi SELECT '???????'         ---- Wrong Query

select *from marathi

just check once the above query in sql, you will understand it. If u write the query using N prefix then in sql it shows the data properly, but if don't use N prefix then it shows ??????? in sql server.
But now my problem is that I am trying to do same from my window application. I wrote the following code.

SqlCommand slc = con.CreateCommand();

slc.CommandText = "Insert into marathi values(@Names)"

slc.Parameters.Add("@Names", SqlDbType.NVarChar, 22);

slc.Parameters["@Names"].Value = textBox1.Text;

slc.ExecuteNonQuery();

How can I achieve this? Please Help....