after start workflow successfully using below code 

Connection conn = new Connection();

////server name
conn.Open("XXXXXX");

////Project nameProcess name
string name = @"XXXXXProcess.kprx";

ProcessInstance pi = conn.CreateProcessInstance(name);

//// set folio number
pi.Folio = "XXXXXXX";

//// Start K2 process instance
conn.StartProcessInstance(pi);

////Close connection to the Client
conn.Close();

How can i move workflow programmatically to next state ??