Cannot implicitly convert type 'System.DateTime?' to 'System.DateTime'

[Lodeclaw]

DateTime dateRented = rental_InvoiceTableAdapter1.getTimeRentedbyInvoiceNo(int.Parse(txtInvoiceNo.Text));

I can't figure out why I'm getting this exception thrown by this code. I'm trying to collect a single cell from the DateTime column "Time_Rented" using a SQL statement. The SQL statement works fine in the query builder, so it has to be something in the C# code. The entire error message is: "Cannot implicitly convert type 'System.DateTime?' to 'System.DateTime'. An explicit conversion exists ( are you missing a case?)" Both sides of the statement are DateTime, aren't they? I don't understand why it can't convert it. Please help!

[Kristian Sixhoj]

Lodeclaw wrote:

System.DateTime?

What is System.DateTime**?** ? I have only heard of System.DateTime. Try removing the "?".

Kristian Sixhoej "You can't undo the past... but you can certainly not repeat it." - Bruce Willis

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[Lodeclaw]

That's confusing me, as well. I didn't type System.DateTime? anywhere. If I had typed it incorrectly the debugger would have notified me when I typed it. I'll do a search for it, anyway.

[Alan N]

Look closely at the message. DateTime? is a nullable DateTime. You'll have to do the explicit conversion [EDIT] or alternatively declare you date rented as the nullable DateTime? type. Alan.

[Lodeclaw]

I've been trying to do the explicit conversion. How do I know what the explicit conversion is? I've tried DateTime.Parse the query results as a string and I've tried Convert.DateTime. Can you offer any other possibilities?

[Ben Fair]

DateTime? is short-hand for Nullable<DateTime>, using the Nullable<T> class introduced in .NET Framework 2.0. The Nullable types are actually a class that is a wrapper around a value type. To get the underlying value from a Nullable<T>, use the Value property like so:

DateTime dateRented = rental_InvoiceTableAdapter1.getTimeRentedbyInvoiceNo(int.Parse(txtInvoiceNo.Text)).Value;

Or you can declare dateRented as Nullable<DateTime> (same as DateTime?) rather than a normal DateTime, like so:

DateTime? dateRented = rental_InvoiceTableAdapter1.getTimeRentedbyInvoiceNo(int.Parse(txtInvoiceNo.Text));

OR

Nullable<DateTime> dateRented = rental_InvoiceTableAdapter1.getTimeRentedbyInvoiceNo(int.Parse(txtInvoiceNo.Text));

The message really means that the getTimeRentedbyInvoiceNo() function is returning a DateTime? and you are trying to stuff that return value into a DateTime; and they are two different types.

Hope in one hand and poop in the other; see which fills up first. Hope and change were good slogans, now show us more than words.

[Lodeclaw]

I tried those and even though the debugger is ok with them, and the other conversions I've tried, I get an exception telling me the input value is not in the correct format.

[Alan N]

Lodeclaw wrote:

I get an exception telling me the input value is not in the correct format.

This may be a different problem now. Where did the exception arise and do you know that the result of int.Parse is valid input for your function? Alan.

[Lodeclaw]

For some reason the query that fills the txtInvoiceNo textbox is not yielding a result, so my input is an empty string. I'll have to figure out why that is. In any case, this problem is solved, then. Thanks everyone for helping this poor noob. :doh: I learned some new things.

[Christian Graus]

It's a nullable datetime. int? is a nullable int, for example.

Christian Graus Driven to the arms of OSX by Vista.