怎摸我这个插入语句有错？

Question

语句如下：
string ttime=this.txtTime.Text;
DateTime dtime=Convert.ToDateTime(ttime.ToString());
string tcard=this.txtCard.Text;
string tprice=this.txtPrice.Text.ToString();
double tmoney=Convert.ToDouble(tprice);
string ttype=this.txtType.Text;
string addword="insert into Trade(TradeDate,CardID,TradeMoney,TradeType) values('"+dtime+"','"+tcard+"','"+tmoney+"','"+ttype+"')";
Sconn=new SqlConnection(strcon);
Scomm=new SqlCommand(strcon,Sconn);
try
{
Sconn.Open();
                Scomm=new SqlCommand(addword,Sconn);
                Scomm.ExecuteNonQuery();
MessageBox.Show("添加成功啦！","添加成功",MessageBoxButtons.OK,MessageBoxIcon.Information);
}
catch(SqlException ex)
{
MessageBox.Show(ex.Message);
}
。。忘了语句~sorry~!