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Old October 24th, 2009, 11:16 AM
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Default Conversion from type 'DBNull' to type 'Boolean' is not valid.

I have a formview that contains OT and PT checkboxes that set to allow nulls in the database. I'm getting the error I've posted below. I've googled the error and "think" I will require codebehind to get past this but for the life of me don't know what to write nor what event it should be put under. I'm used to programming in Access so this is still pretty new to me and frustrating!!! Any help would be appreciated.


Conversion from type 'DBNull' to type 'Boolean' is not valid.

Source Error:

Line 402: <asp:Label ID="GradeLabel" runat="server" Text='<%# Bind("Grade") %>'></asp:Label><br />
Line 403: OT:
Line 404: <asp:CheckBox ID="OTCheckBox" runat="server" Checked='<%# Bind("OT") %>' Enabled="false" /><br />
Line 405: PT:
Line 406: <asp:CheckBox ID="PTCheckBox" runat="server" Checked='<%# Bind("PT") %>' Enabled="false" /><br />
Old October 24th, 2009, 06:53 PM
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Before you can handle this, you need to decide exactly how you intend to display a null OT or a null PT.

Right now, you are attempting to display a three-valued property with a two-valued control. In other words, there are THREE possible values for OT and PT: true, false, and NULL. However, there are only two states for a checkbox: checked and unchecked.

You would normally show a true value with a checked checkbox; and a false value with an unchecked checkbox. But, how do you intend to display a NULL value for OT or PT?

You could write code to show a NULL value as an unchecked checkbox, for example. But that way, there is now way to distinguish a NULL from a false when the values are displayed. Does that make sense?
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Old October 24th, 2009, 10:15 PM
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I'm sorry for posting twice. I was having trouble with my internet and the page seemed to be stuck.

Under Misc. in the properties I have checked = false. Is this what you mean?

Old October 27th, 2009, 03:07 PM
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What he is saying is that a checkbox can only have 2 possible values, TRUE or FALSE. The problem you are having is that you are getting NULL values and a checkbox does not know how to display that. What you have to decide is that when you get a NULL back from your datasource, how do you want to display the checkbox, as checked or not checked?

I think the main problem here is that a boolean/bit data type should not allow NULLs.
Old October 28th, 2009, 03:38 AM
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Send a message via Yahoo to melvik

u may set a default for ur field in Dataset or use IsNull() in DB
Hovik Melkomian.

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