C# “00”附近的语法不正确

我是asp和sql server的新手。我在sql查询中遇到问题

string obal ;
        decimal _obalss = 0;
        decimal obalss = 0;
        sconnection c = new sconnection();
        string cus_id = Session["cusid"].ToString();
        DateTime maxdate = DateTime.Parse(fromdt.Text, new System.Globalization.CultureInfo("en-US"));
        string mdate = maxdate.ToString();
        string query_sl = "select sum(amount) as amount from sale where cusid = " + cus_id + " and invdate < " + maxdate + " group by cusid"; 
        SqlDataReader dr = c.reader(query_sl);
        if (dr.Read())
        {
            decimal.TryParse(dr["amount"].ToString(), out _obalss);
            obalss = _obalss;
        }
        else
        {
            obalss = 0;
        }
            dr.Close();
            dr.Dispose();

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请注意maxdate周围的单引号…

Quick note:这与ASP.NET无关，而与SQL有关。放置断点并查看哪个查询生成到query_sl string变量中，将其发布到此处，以便我们可以看到哪个查询实际执行了参数化查询至少+1。

 string query_sl = "select sum(amount) as amount from sale where cusid = " + cus_id + " and invdate < " + maxdate + " group by cusid"; 

string query_sl = "select sum(amount) as amount from sale where cusid = @CUSID and invdate < @MAXDATE group by cusid"; 
using(SqlCommand cmd = new SqlCommand(query_sl, c))
{
    cmd.Parameters.Add(new SqlParameter("@CUSID", SqlDbType.Int)).Value = cus_id;
    cmd.Parameters.Add(new SqlParameter("@MAXDATE", SqlDbType.DateTime)).Value = maxdate;
    ...
}

string query_sl = "select sum(amount) as amount from sale where cusid = " + cus_id + " and invdate < '" + maxdate + "' group by cusid";