How To create connectivity with class file in .net windows application

// This code type in your class file.

public static object execmd(string qur)

        {

            OleDbConnection con = new OleDbConnection(constr);

            OleDbCommand cmd = new OleDbCommand(qur, con);

            con.Open();

            return cmd.ExecuteScalar();

        }

//This code type in your form

private void button1_Click(object sender, EventArgs e)

{

string str="      ";

namespace.classname.execmd(str);

messagebos.show("Data Is Submitted");

}