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Cor Ligthert said:Hi Dave,
if (dataset1.SelectQuery.column1 == null) // there is a null value
Cor
Dave said:If Iwant to check if dataset1.SelectQuery1.column1 ==
System.DBNull.Value. How do I do this? What I wrote above will give an
error.
I tried the statement: dataset1.SelectQuery.column1 == null and I got the
error:
System.Data.StrongTypingException was unhandled
Message="The value for column 'TaxType' in table 'TaxSelect' is DBNull."
Source="Retail"
StackTrace:
if (dataset1.SelectQuery.column1 == null) // there is a null value
DbNull.Value doesn't equal null... The above line will generate an error
if column1 contains DbNull
Mark Rae said:if (dataset1.SelectQuery.column1 == null) // there is a null value
DbNull.Value doesn't equal null... The above line will generate an error
if column1 contains DbNull
Cor Ligthert said:Mark,
DbNull.Value doesn't equal null... The above line will generate an error if
column1 contains DbNull
In my idea can a column not contain a db.null value. There is just no value.
I was overreading that it was a strongly typed dataset, which will in most
types catch the DBNull.value themselves.
Which means that if a row in the database exist with a null value (what
should be impossible with a good one) while that should not, will thrown an
error.
Cor
Mark Rae said:if (dataset1.SelectQuery.column1 == null) // there is a null value
DbNull.Value doesn't equal null... The above line will generate an error if
column1 contains DbNull
Cor Ligthert said:Mark,
DbNull.Value doesn't equal null... The above line will generate an error
if column1 contains DbNull
In my idea can a column not contain a db.null value. There is just no value.
I was overreading that it was a strongly typed dataset, which will in most
types catch the DBNull.value themselves.
Which means that if a row in the database exist with a null value (what
should be impossible with a good one) while that should not, will thrown an
error.
Cor
Mark Rae said:if (dataset1.SelectQuery.column1 == null) // there is a null value
DbNull.Value doesn't equal null... The above line will generate an error
if column1 contains DbNull
Dave said:If Iwant to check if dataset1.SelectQuery1.column1 ==
System.DBNull.Value. How do I do this? What I wrote above will give an
error.
Bart Mermuys said:Hi,
Dave said:If Iwant to check if dataset1.SelectQuery1.column1 ==
System.DBNull.Value. How do I do this? What I wrote above will give an
error.
If you use a typed DataSet, then you must use the Set???Null and Is???Null
functions (where ??? is the name of the column), eg. :
if ( dataset1.SelectQuery.Iscolumn1Null() )
{
}
HTH,
Greetings
Dave said:Dear Cor Ligthert,
You mentioned: "...if a row in the database exist with a null value (whatshould be impossible with a good one) while that should not...". My
question
is: Suppose I have a table with columns which allow nulls, then how can I
prevent DBNulls from being placed in that column considering that I prefer
not place an empty string in the column. What effect does placing an empty
string in a column have on the database (specifically in terms of database
size) compared to if a column was set to DBNull?
Additionally, I have seen this thread address most the "why" issues. I
understand most of it. But could you show the "how" factor.
--
L. A. Jones
Cor Ligthert said:Mark,
DbNull.Value doesn't equal null... The above line will generate an
error
if column1 contains DbNull
In my idea can a column not contain a db.null value. There is just no
value.
I was overreading that it was a strongly typed dataset, which will in
most
types catch the DBNull.value themselves.
Which means that if a row in the database exist with a null value (what
should be impossible with a good one) while that should not, will thrown
an
error.
Cor
Mark Rae said:if (dataset1.SelectQuery.column1 == null) // there is a null value
DbNull.Value doesn't equal null... The above line will generate an
error
if column1 contains DbNull
Suppose I have a table with columns which allow nulls, then how can I
prevent DBNulls from being placed in that column considering that I prefer
not place an empty string in the column
What effect does placing an empty
string in a column have on the database (specifically in terms of database
size) compared to if a column was set to DBNull?
Additionally, I have seen this thread address most the "why" issues. I
understand most of it. But could you show the "how" factor.
Gopal said:Hi..
you can check the column value with DBNull like this..
if(dataset1.SelectQuery1.column1.Equals(System.DBNull.Value))
{
// logic goes
}
Regards,
Gopal
If Iwant to check if dataset1.SelectQuery1.column1 ==
System.DBNull.Value. How do I do this? What I wrote above will give an
error.
It will work if you set NullValue to [Null] or [Empty] in the XSD designer,
but only if "column1" is Typed as System.String.
Dave Sexton said:Hi Gopal,
It will work if you set NullValue to [Null] or [Empty] in the XSD designer,
but only if "column1" is Typed as System.String.
Any other Type for "column1" will always throw an exception when reading a
DBNull value. You can verify this by trying to change NullValue in the XSD
designer to anything other than [Throw Exception], for any column that is
not System.String.
--
Dave Sexton
Gopal said:Hi..
you can check the column value with DBNull like this..
if(dataset1.SelectQuery1.column1.Equals(System.DBNull.Value))
{
// logic goes
}
Regards,
Gopal
If Iwant to check if dataset1.SelectQuery1.column1 ==
System.DBNull.Value. How do I do this? What I wrote above will give an
error.
In my idea is the "best" method (whatever that is) for that using binding
and than the binding events.
A real sarcastic reply, however it shows only a lot about your knowledge.
Mark Rae said:Not sarcastic at all. In fact, with my degree in foreign languages I can
usually just about decipher your posts, but the above had me stumped...
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