PostgresException：42883：運算符不存在：@字符變化

Question

我正在嘗試在 razor 頁 c# 中進行預訂頁面。如果我進行預訂，它也會出現在用戶的頁面上。 我在每個預訂旁邊都做了一個按鈕，這樣你就可以刪除預訂。 預訂在頁面上僅顯示日期和位置。 當我嘗試從頁面中刪除它時出現此錯誤：PostgresException: 42883: operator does not exist: @ character varying 並且不知道為什么。 這是 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，這是 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>

---

編輯：

錯誤得到解決，但由於某種原因，特定行沒有從數據庫中刪除。 什么都沒發生。 這就是我對代碼所做的更改。

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

它試圖將“@”解析為“=@”

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

字面意思是傳遞給 Db。 您需要構建該字符串，以便相應地填充 @LocationID 和 @convdaid。 就像是：

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