Error in Asp.net

Question

using System.Data.OleDb;

public partial class _Default : System.Web.UI.Page 

{

    public OleDbConnection oledbcon;

    protected void Page_Load(object sender, EventArgs e)

    {

        String constr;

        constr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source='C:\\Student.mdb'; Persist Security Info=False";

        oledbcon = new OleDbConnection(constr);

        oledbcon.Open();

    }

    protected void Button1_Click(object sender, EventArgs e)

    {

        String sqlstr;

        String sname;

        String percentage;

        String id;

        id = TextBox1.Text;

        sname = TextBox3.Text;

        percentage =TextBox2.Text;

        OleDbCommand cmd;

        sqlstr = "insert into stud values('id','sname','percentage')";

        //sqlstr = "select * from stud";

        cmd = new OleDbCommand(sqlstr);

        cmd.Connection = oledbcon;

        cmd.ExecuteNonQuery();

        //cmd.ExecuteReader();

        Response.Write("data saved successfully");

    }

}

in ms Acess07 

id(P.K.)as number

sname as text

percentage as text

Error::Data type mismatch in criteria expression.(at line cmd.executenonquery())

whether we have to convert string to number?? and if yes then how to do it??