executenonquery commandtext property has not been initialized : when i click on this button , i face with this error

> executenonquery commandtext property has not been initialized

private void button_FirstStep_Click(object sender, EventArgs e)
        {
            
            SqlConnection Conn = new SqlConnection(Yahya.strcon);
            Conn.Open();
            int CurrentCount = Convert.ToInt32(label_CurrentCount.Text);
            string strcom1 = "select * from vm1 where count = '" + (CurrentCount - 1) + "' and benchmarkid = '" + Structure.BenchmarkID + "' ";
            SqlCommand cmd = new SqlCommand(strcom1, Conn);
            SqlDataReader reader = cmd.ExecuteReader();
            string strcom = "";
            while (reader.Read())
            {
                if (reader["vmid"].ToString() != "")
                {
                    string vmid = reader["vmid"].ToString();
                    strcom += "update vm1 set pmid = (select pmid from vm1 as VM2  where   benchmarkid = '" + Structure.BenchmarkID + "' and  vm2.count ='" + (CurrentCount - 1) + "' and vm2.vmid ='" + vmid + "' ) where count  =  '" + CurrentCount + "'  and vmid = '" + vmid + "' and  benchmarkid = '" + Structure.BenchmarkID + "'  \n";

                }
            }//end of while
            reader.Close();
            cmd.CommandText = strcom;
            cmd.ExecuteNonQuery();



 