PostgresException：42883：运算符不存在：@字符变化

Question

我正在尝试在 razor 页 c# 中进行预订页面。如果我进行预订，它也会出现在用户的页面上。 我在每个预订旁边都做了一个按钮，这样你就可以删除预订。 预订在页面上仅显示日期和位置。 当我尝试从页面中删除它时出现此错误：PostgresException: 42883: operator does not exist: @ character varying 并且不知道为什么。 这是 c# 端：

public void OnPostRemove(ReservationModel reservation)
{
    DateTime convdayid = Convert.ToDateTime(reservation.Dayid);
    DeleteReservation(convdayid, reservation.Locationid);
}

public void DeleteReservation(DateTime convdayid, string Locationid)
{
    
    var cs = Database.Database.Connector();
    using var con = new NpgsqlConnection(cs);
    con.Open();

    var sql = "DELETE FROM reservation WHERE locationid = @Locationid AND dayid = @convdayid;";
    using var cmd = new NpgsqlCommand(sql, con);
    cmd.Parameters.AddWithValue("locationnid", Locationid);
    cmd.Parameters.AddWithValue("dayid", convdayid);
    cmd.Prepare();
    cmd.ExecuteNonQuery();

}

如果需要，这是 html 端

@foreach(var reservations in @Model.ShowReservation())
{
    <form method="post">
        <fieldset>
            <div class="form-group">
                <tr>
                    <img class="img-fluid" src="/Images/Reservation.png"/>
                    <td>
                        @Html.DisplayFor(m => reservations.Dayid)
                        <input type="hidden" name="Dayid" value="@Html.DisplayFor(m => reservations.Dayid)"/>
                    </td>
                    <td>
                        @Html.DisplayFor(m => reservations.Locationid)
                        <input type="hidden" name="Locationid" value="@Html.DisplayFor(m => reservations.Locationid)"/>
                    </td>
                </tr>
                <button type="submit" value="Submit" asp-page-handler="Remove" class="btn btn-dark btn-sm">X</button>
            </div>
        </fieldset>
    </form>
    <hr>
}
<hr>

---

编辑：

错误得到解决，但由于某种原因，特定行没有从数据库中删除。 什么都没发生。 这就是我对代码所做的更改。

public void OnPostRemove(ReservationModel reservation)
        {
            DateTime convdayid = Convert.ToDateTime(reservation.Dayid);
            DeleteReservation(convdayid, reservation.Locationid);
        }

        public void DeleteReservation(DateTime convdayid, string Locationid)
        {
            
            var cs = Database.Database.Connector();
            using var con = new NpgsqlConnection(cs);
            con.Open();

            var sql = "DELETE FROM reservation WHERE locationid = @locationid AND dayid = @dayid;";
            using var cmd = new NpgsqlCommand(sql, con);
            cmd.Parameters.AddWithValue("locationid", Locationid);
            cmd.Parameters.AddWithValue("dayid", convdayid);
            cmd.Prepare();
            cmd.ExecuteNonQuery();

        }

Answer 1

它试图将“@”解析为“=@”

DELETE FROM reservation WHERE locationid = @Locationid AND dayid = @convdayid;

字面意思是传递给 Db。 您需要构建该字符串，以便相应地填充 @LocationID 和 @convdaid。 就像是：

DELETE FROM reservation WHERE locationid = 34 AND dayid = 55;