Back when I coded in Visual Studio 2003, we used to joke that if you wrote a small app that had 100 lines of code, 98 of them would be checking for nulls. It actually wasn’t that far off.
Because of that, I often force my DTO’s to default to DateTime.MinValue instead of nulls and have my code look for MinValue rather than checking for nulls all the time. This has one side effect that I didn’t like, when you use your model in an MVC view, it will display in the text box like “01/01/0001 00:00:00” etc. This is obviously not desirable.
The secondary issue is that when you use Date/Time pickers in the view, they don’t like being bound to DateTime properties, they work better on a string based text box. So what I’ve done is resolve both issues with one solution.
First part is in the ViewModel. I often just inherit my DTO and add or override properties with Attributes/Decorations that I need for the View. I’ll use my ProjectViewModel as an example:
public class ProjectViewModel : Project
{
/// <summary>
/// Gets or sets the Project Start Date Display
/// Use to get rid of 01/01/0001 displays
/// </summary>
[Display(Name = "Start Date: ")]
public string StartDateDisplay
{
get
{
return StartDate.ToShortDateDisplay();
}
set
{
StartDate = value.ToDateFromString();
}
}
}
In this case, my Project DTO has a StartDate property that is a DateTime. It could be null, or it could be DateTime.MinValue, or it could be a real date. In this implementation, I don’t care about the time, but you could build this out to include time very easily.
When I use this in a view, I use the StartDateDisplay property, rather than the StartDate property.
@Html.TextBoxFor(model => model.StartDateDisplay, new { @class = "form-control", @id = "txtStartDate", @title = "Project Start Date", @type = "text", autocomplete = "off" })
Now this will play nice with the Date/Time picker because it is a string property.
In order to get the dates formated, you’ll notice the ToShortDateDisplay() and the ToDateFromString() extension methods. Those are defined as:
/// <summary>
/// Convert a date to a short date string, empty if min or max value
/// Yasgar Technology Group, Inc. - www.ytgi.com
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
public static string ToShortDateDisplay(this DateTime value)
{
if (value == null) { return string.Empty; }
if ((value == DateTime.MaxValue) || (value == DateTime.MinValue))
{
return string.Empty;
}
else
{
return value.ToShortDateString();
}
}
/// <summary>
/// Convert a string in MM/DD/CCYY format to a valid date
/// Yasgar Technology Group, Inc. - www.ytgi.com
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
public static DateTime ToDateFromString(this string value)
{
if (!string.IsNullOrWhiteSpace(value))
{
if ((value == "99999999") || (value == "99/99/9999"))
{
return DateTime.MaxValue;
}
else
{
if (!string.IsNullOrWhiteSpace(value))
{
DateTime _value;
DateTime.TryParse(value, out _value);
return _value;
}
else
{
return DateTime.MinValue;
}
}
}
return DateTime.MinValue;
}
Solved two issues with one solution. No checking for nulls, no checking for DateTime.MinValue.
