An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll in Winform C#

Can Anyone help me? I'm using SQL2014 and my code as below:

void loadProductsInfor()
        {
            SqlConnection con = new SqlConnection();
            con.ConnectionString = @"server=
.\SQLEXPRESS;database=CNET_Block3;
                                             uid=sa;pwd=123456;integrated security=true";
            con.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "SELECT * FROM Products";
            **SqlDataReader dr = cmd.ExecuteReader(); (Exception appears at this line)**
            while (dr.Read())
            {
                dataGridView1.Rows.Add(dr[0].ToString(), dr[1].ToString(), dr[2].ToString(), dr[3].ToString(),
                    dr[4].ToString(), dr[5].ToString(), dr[6].ToString(), dr[7].ToString(), dr[8].ToString(),
                    dr[9].ToString(), dr[10].ToString());
            }
            dr.Close();
            con.Close();
        }

I tried many things but they didn't work. I have a practical exam in the next 2 days. Please give me a hand.