how do I handle the DBNull fields

1/ I have a checkBox that I want to fill with a value from a Bit field in SQL server. But when the field has a Null value, it gives me an error. How do I convert the DBNull value to a boolean and how do I handle the DBNull values of my table columns.

2/ One more question: I ve seen a technical document about handling Null values from the database in the MSDN articles, but I didn t keep the URL. Does any body know it pls.

Thanks.

Answer this question

how do I handle the DBNull fields

Harlow Burgess
Open the XSD file. For the field giving you the trouble, change the NullValue property to (Null). It's probably currently set to (ThrowException).
Avis Phoenix

You can compare it against DBNull.Value

Ex:

foreach (DataRow dtRow in dsTable.Tables[0].Rows )

Response.Write(dtRow[0]== DBNull.Value "Null Value" : dtRow[0].ToString() );

Thanks.
pppeterd

u gave me en example while using a sqldatareader. that s perfect.

How about when I am using a dataset populated by a sqlDataadapter instead.

Thanks
Rufus Leonard
hi,
sorry men, i think it is very simple to handle but prob. is not clear so i can not give any truth suggestion.
bye
Rajat
LouMachado
Compare the field value with IsDBNull and set the checkbox as true or false as required.

Ex: Datareader.IsDBNull(0)

MSDN article for handling Null Values: http://msdn2.microsoft.com/en-us/ms172138.aspx

Thanks.
William Zhi
These examples are not working for me. I've tried every way I could think (so far) and I always get the same error.

Here's one of the ways I've tried:

if(dtMember[0].CCexp.Equals(System.DBNull.Value))

{

}

At runtime I always get this exception:

catch (System.InvalidCastException e) {

throw new System.Data.StrongTypingException("The value for column \'CCexp\' in table \'Members\' is DBNull.", e);

I've tried using "==" instead of equals. I've tried using "Convert.IsDBNull"...

What am I doing wrong

EDIT:

Wow, I just realized that this exception is built into the column!

public System.DateTime CCexp {

get {

try {

return ((System.DateTime)(this[this.tableMembers.CCexpColumn]));

}

catch (System.InvalidCastException e) {

throw new System.Data.StrongTypingException("The value for column \'CCexp\' in table \'Members\' is DBNull.", e);

}

}

So there's no way for me to even get to the value in this field because as soon as I try to get it, if it's null, I get an exception! I can't even use a try/catch expression. I really hope someone can explain this!
Ilia Broudno
thank you
Bill Christian

>>Wow, I just realized that this exception is built into the column!

It sure is!! I'm having the same problem. Anyone know of a solution

Thanks
how do I handle the DBNull fields

Answer this question