how to set calendar control value as null

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i'm using a Calendar control in a formview, and having problems only when no date is selected,in sql one default date is comming.this field is not a mandortary field,when we select date then only value want to come otherwise we want null vale. How can i fix this issue.

Posted 26-May-15 5:45am

Unni R

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DamithSL 26-May-15 11:55am

update the question with related code samples

ZurdoDev 26-May-15 11:58am

You need to explain where you are stuck. This is not clear.

ZurdoDev 26-May-15 12:04pm

This does not tell me anything. What do you need?

ZurdoDev 26-May-15 12:17pm

Then check for 1/1/1900 and pass in DBNull.Value instead.

Sergey Alexandrovich Kryukov 26-May-15 17:36pm

This is dirty. Too bad this control works this way, but even then it should be DateTime.MinValue, which is too bad anyway. Please see my answer.
—SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-05-26T06:28:00

I think the control System.Web.UI.WebControls.Calendar is defective in this respect. MSDN documentation says that the default value is DateTime.MinValue. This is a shame, really. It means this value, otherwise valid, is used in this control is roughly equivalent to "no-value" or "unset" status. This is wrong. Please see:
https://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.calendar.selecteddate%28v=vs.110%29.aspx[^].

Note that you cannot have null for System.DateTime type, because it is a value type, not a reference type. You could use the nullable type System.DateTime? instead. Too bad, this is not how this control works.

Any practical work-around? Well, you can subclass this control, create a derived class "NullableCalendar". Add additional property of the System.DateTime?. Internally, handle the event SelectionChanged:
https://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.calendar.selectionchanged%28v=vs.110%29.aspx[^].

In the handler, when some "real" date is selected, assign your nullable property to SelectedDate. This way, you will be able to tell "never selected" status of the control by checking this property for null from the "really selected". Think about some custom rendering (such as background color) which would indicate this "never selected" status visually.

—SA