how to send null value to an Integer type variable?

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Learner - 27 Jul 2006 20:38 GMT

Hello,
I have database field called 'PullAHead' defined as a bit field.
Now if user doesn't pick a 'Yes' or 'No' in the front I need to be able
to send a null value into the 'PullAHead' field in the database.

This is how I am trying to do it....

Dim PullAhead As Integer
PullAhead = Nothing
If _lblpullahead.Visible = True Then
PullAhead =
Convert.ToInt32(_drplPullAhead.SelectedValue.Trim)
End If

and finally I am sending the PullAhead integer variable to the
parameters list. But it is sending 0 (i.e I see False in the database
as its a bit field).

Could some one help me here how do I send a null value to the PullAHead
field?

Thanks
-L

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Jay B. Harlow [MVP - Outlook] - 27 Jul 2006 20:48 GMT

Learner,
Generally I use Boolean variables for Bit fields.

Starting with VS 2005 I normally use Nullable(Of T) for value types (such as
Integer & Boolean) that can contain Null.

Dim PullAhead As Nullable(Of Integer)
PullAhead = Nothing
If _lblpullahead.Visible = True Then
PullAhead = Convert.ToInt32(_drplPullAhead.SelectedValue.Trim)
End If

http://msdn2.microsoft.com/en-us/library/b3h38hb0.aspx

Signature

Hope this helps
Jay B. Harlow [MVP - Outlook]
.NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net

| Hello,
| I have database field called 'PullAHead' defined as a bit field.
[quoted text clipped - 19 lines]
| Thanks
| -L

Reply to this Message

Learner - 27 Jul 2006 23:17 GMT

Hello Jay,
Thank you for the suggestion. Its a good one that I have learnt from
your posting today :) Now I am changing it to Boolean from integer as
you suggested.

So now the code looks like this

Dim PullAhead As Nullable(Of Boolean)
PullAhead = Nothing
If _lblpullahead.Visible = True Then
PullAhead = Convert.ToInt32(_drplPullAhead.SelectedValue.Trim)
End If

Hope full the above code snippet make sense I guess or else please do
post it one more time. And one more question it the line of code Dim
PullAhead As Nullable(Of Boolean)
we are already initializing it null (am I right here?) do you think I
still need to assign Nothing in the line of code PullAhead = Nothing?

Please bear with my english.

Thanks
-L

> Learner,
> Generally I use Boolean variables for Bit fields.
[quoted text clipped - 39 lines]
> | Thanks
> | -L

Reply to this Message

Jay B. Harlow [MVP - Outlook] - 27 Jul 2006 23:56 GMT

| we are already initializing it null (am I right here?) do you think I
| still need to assign Nothing in the line of code PullAhead = Nothing?

The compiler will implicitly initialize it to Nothing, you don't need to
assign Nothing to it per se...

Signature

Hope this helps
Jay B. Harlow [MVP - Outlook]
.NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net

| Hello Jay,
| Thank you for the suggestion. Its a good one that I have learnt from
[quoted text clipped - 63 lines]
| > | Thanks
| > | -L

Reply to this Message

Learner - 01 Aug 2006 12:47 GMT

Hello Jay,
I tried with this but when I send this as a parameter to a method in
my Business Layer
its throwing this error

*********************************************************************************************
System.InvalidOperationException was unhandled by user code
Message="Nullable object must have a value."
Source="mscorlib"
StackTrace:
at
System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource
resource)
at System.Nullable`1.op_Explicit(Nullable`1 value)
at DealerQuestionsUS._btnGround_Click(Object sender, EventArgs
e) in
D:\VSProjects\GroundingDemo\GroundingDemo\DealerQuestionsUS.aspx.vb:line
143
at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String
eventArgument)
at
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String
eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler
sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection
postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
********************************************************************************************

Am I missing some thing here?
the code is exactly the same as we discussed in our previous postings.

Thanks
-L

> | we are already initializing it null (am I right here?) do you think I
> | still need to assign Nothing in the line of code PullAhead = Nothing?
[quoted text clipped - 77 lines]
> | > | Thanks
> | > | -L

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how to send null value to an Integer type variable?

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