DateTime filter

Question

I have been trying to optimize the filtering process of a Collection<Alert> based on the DateTime GeneratedOn property of Alert class.

Below is the code block which filters the List by taking in From Date and To Date.

if (this.Alerts != null)
 {
 var fromDt = Convert.ToDateTime(this.FromDateAlert.ToShortDateString() + " " + this.FromTimeAlert.ToLongTimeString());
 var toDt = Convert.ToDateTime(this.ToDateAlert.ToShortDateString() + " " + this.ToTimeAlert.ToLongTimeString());
 if (fromDt > toDt)
 {
 Messages.InfoMessage("FromDate cannot be greater than ToDate", "Alert"); return;
 }
 this.IsBusy = true;
 var filteredAlerts = this.Alerts.Where(a => (DateTime.Parse(a.Created) >= fromDt) && (DateTime.Parse(a.Created) <= toDt)); 
 this.PagedAlerts = new PagedCollectionView(filteredAlerts);
 this.IsBusy = false;
 }

Is there a better way of doing this?

• svick: You mean you're trying to make this code faster? Did profiling tell you this code is really a bottleneck in your application?
• svick: But my primary advice would be to try to avoid strings for representing dates and times as much as possible. Certainly don't use them to combine a date with a time, that will be slow and unreliable.
• noor syyed: I want a very precise filtering that can even filter out records based on time, that's why I combined the Date and Time, by converting it to ToShortDateString() and ToLongTimeString().
• svick: Yeah, but I don't see any reason why you would use strings for that. You should work only with the DateTimes directly.

Answer 1

Why are you storing FromDate and FromTime seperately to begin with?

Instead of storing using four properties, use only two, storing both Date and TimeOfDay inside them:

public DateTime FromAlert { get; private set; }
public DateTime ToAlert { get; private set; }

In the following code:

var fromDt = Convert.ToDateTime(this.FromDateAlert.ToShortDateString() + " " + this.FromTimeAlert.ToLongTimeString());
var toDt = Convert.ToDateTime(this.ToDateAlert.ToShortDateString() + " " + this.ToTimeAlert.ToLongTimeString());

You are converting multiple DateTime values to strings in order to parse them again (this should immediately raise a red flag). When you use the DateTime fields like they were meant to (i.e. containing both Date and TimeOfDay), you can get rid of these redundant conversions:

if (FromAlert > ToAlert)
{
 Messages.InfoMessage("FromDate cannot be greater than ToDate", "Alert"); 
 return; //always put this on a separate line!!
}

I have been trying to optimize the filtering process of a Collection based on the DateTime
GeneratedOn property of Alert class.

And why are you parsing the string Alert.Created if you already have a DateTime Alert.GeneratedOn? Just use it:

var filteredAlerts = Alerts.Where(a => a.GeneratedOn >= fromDt && a.GeneratedOn <= toDt);

• noor syyed: Hi @codesparkle thanks for your valuable post. For some strange and anonymous reason I had been getting the Alert's CreatedOn prop as a string. So I went up to that guy who was associated with this retrieving Alerts of a system from system center operations manager and asked him why can't you just get CreatedOn as DateTime instead of a string so he changed its type to DateTime. The whole mess of multiple conversions and parsing was 'cause of the CreatedOn prop being a string type.