using (SqlConnection connection = new SqlConnection(SQLConnString))
  {
      // Create the command and set its properties.
      SqlCommand command = new SqlCommand();
      command.Connection = connection;
      command.CommandText = "ReadSomeData";
      command.CommandType = CommandType.StoredProcedure;

      // Add the input parameter and set its properties.
      SqlParameter parameter = new SqlParameter();
      parameter.ParameterName = "@Result";
      parameter.SqlDbType = SqlDbType.VarChar;
      parameter.Size = 2000;
      parameter.Direction = ParameterDirection.Output;

      // Add the parameter to the Parameters collection. 
      command.Parameters.Add(parameter);

      // Open the connection and execute the reader.
      connection.Open();
      command.ExecuteNonQuery();

      // String s = parameter.Value.ToString();
      // ?? как достать значение параметра, не приводя к Unicode


      connection.Close();
  }