LINQ 查询比较 DateTime 列与 DateTime 字符串列

Question

I have a table with 3 columns like below：

DeliveryDate(string) | 2020-06-16
DeliveryTime(string) | 20:00:00
EstimateDeliveryDateTime(DateTime) | 2020-06-15 20:00:00.232

I wrote below condition in LINQ, expect it convert to sql by ef core, but failed. EstimateDeliveryDateTime > Convert.ToDateTime(DeliveryDate + DeliveryTime)

I know AsEnumberable(). But I want this condition to be executed in db, is it doable in LINQ or not?

Answer 1

How about using DateTime.ParseExact?

EstimateDeliveryDateTime > DateTime.ParseExact(DeliveryDate + DeliveryTime, "yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture")

Hope it will be helpful.

Answer 2

EstimateDeliveryDateTime > Convert.ToDateTime(DeliveryDate + " " + DeliveryTime)

Answer 3

You can write your own method/extention method to convert the string to DateTime according to the string format ie. yyyy-dd-MM hh:mm:ss ie. yyyy-dd-MM hh:mm:ss .
Here is my suggestion:

Implementation:

private void Example()
{
    string DeliveryDate = "2020-06-16";
    string DeliveryTime = "20:00:00";
    DateTime EstimateDeliveryDateTime = DateTime.Now;

    if (EstimateDeliveryDateTime < DeliveryDate.ToDate(DeliveryTime))
    {
        // do something....
    }
}

Extension Method:

public static DateTime ToDate(this string wanabedate, string wanabetime)
{
    try
    {
        string[] mydate = wanabedate.Split('-').ToArray();
        if (mydate == null || mydate.Length < 3)
        {
            return DateTime.MinValue;
        }

        string[] mytime = wanabetime.Split(':');

        // create date time
        var year = Convert.ToInt32(mydate[0]);
        var day = Convert.ToInt32(mydate[2]);
        var month = Convert.ToInt32(mydate[1]);

        var seconds = Convert.ToInt32(mytime[2]);
        var mins = Convert.ToInt32(mytime[1]);
        var hr = Convert.ToInt32(mytime[0]);

        DateTime result = new DateTime(year, month, day, hr, mins, seconds, 0);

        return result;
    }
    catch (Exception ex)
    {
        return DateTime.MinValue;
    }
}

Answer 4

Finally, I create a sql View convert DeliveryDate + DeliveryTime to one DateTime column. And then use ef core keyless entity to query the View.