I have a date field in my database (StartDate). I have created a datatable which will access this field. The DataType in the DataTable is defined as System.DateTime. Allow DBNull is set to True and th DefaultValue is <DBNull>. I have an SQL statement to add (INSERT) a new record. I have created a parameter to be used with the SQL statement. In the parameter options I have set AllowDBNull to true, the DbType is set to Date and the ProviderType is DBDate. Everything works great as long as the date textbox has a date in it. The problem is there is not always a date provided to a DBNull value should added. When I try to run the SQL statement with no date provided I get the following error message:

Conversion from string "" to type 'Date' is not valid.

I have tried many things but cant seem to get rid of the error.

Thanks for any help,


Re: Visual Basic Express Edition Add DBNull to date field in database?


I have had some issues with this also.

It took this happening to me twice and then i got rid of the datetime types.

I set all my fields to either varchar or nvarchar and then i handle the formatting myself in my entry forms.

by setting to variable characters (varchar) then you can have anything you want in the field and that includes "" (null)

I guess the issue on the datetime type is that an empty string can never be a date but an empty string is still a string in a string field.

For my dates i use a datetimepicker to enter the date and format it how i want it. This takes out the guess work for the user. And for times i use a combobox that is populated with times for them to choose from. I even place the datetimepicker under the textbox for the datetime field and then hide it. I have a button next to the box that when clicked will show the picker and when they select a date it will hide again.

All these preset formats get difficult to handle sometimes. I haven't played with it because i don't use a datagridview for entering data, i use only textboxes, but i would imagine you could handle the keypress events for the datagridview also when editing by determining what column index you are in and then control the keypresses.

I like to stay away from a lot of the preset "stuff"

By the way, did you see the code i gave you in the other thread about bindingsource with option strict on

The code will give you what you need and still be option strict safe.

Re: Visual Basic Express Edition Add DBNull to date field in database?


Hi JS. We meet again. Sounds like I should just get your Windows Messenger screen name Smile I would like to be able to use DateTimePicker but when a project is entered it does not always have start and/or end dates so nothing is entered which results in a "" string which cant be converted to a date. I have tried everything I could think of. I did find that sending "Nothing" instead of "" or DBNull does work and I dont get the error.

I did get your solution for my question in the other thread but I haven't had the chance to try it yet.

This is the first time I have tried any kind of data access in .NET, which is of course the reason for all the recent questions. Usually I work on applications that require some sort of data acquisition via data acquisistion boards.

Thank for the help,


Re: Visual Basic Express Edition Add DBNull to date field in database?


I actually meant to say monthcalendar, not datetimepicker.

the datetimepicker will always show a value in it. I'm not sure if you can prevent it or not.

but the monthcalendar is not automatically shown in a textbox so you can add the selected date to a textbox if one is chosen.

After a while all the names start to sound the same on some things.

Maybe i am just tired here lately

And about messenger, i don't do any chat. I strictly stay in the forum.