DataColumn.Expression

[Christopher Dedels]

How canI get the DataColumn.Expression property handle trigonometric
functions?

For example:
I have a DataTable with 1 columns named "x". I want to add a column that
shows sin(x).

dataset.Tables["trigsample"].Columns.Add("sinx", typeof(double));
dataset.Tables["trigsample"].Columns["sinx"].Expression = "sin(x)";

Any help or ideas you may have are appreciated.

Thanks,

Chris

 

[William Ryan eMVP]

Hi Chris:

Sin isn't supported by the Expression Syntax. You can do quite a bit and
can probably do it yourself using the available expression
http://msdn.microsoft.com/library/d...fSystemDataDataColumnClassExpressionTopic.asp
but in this instance, you may want to do it on the Sever side or manually
calculate it and add it to the row programatically. Normally this isn't a
good idea b/c expressions automatically update themselves when any of their
source column data changes, but while the Expression values available are
pretty accomodating, they aren't unlimited.

HTH,

Bill

 

[Christopher Dedels]

Bill,

Thanks for the response. I was hoping to be able to get the automatic
recalculation if the source data changed. I had a feeling this was not
possible. Too bad.

Chris

Hi Chris:

Sin isn't supported by the Expression Syntax. You can do quite a bit and
can probably do it yourself using the available expression
http://msdn.microsoft.com/library/d...fSystemDataDataColumnClassExpressionTopic.asp
but in this instance, you may want to do it on the Sever side or manually
calculate it and add it to the row programatically. Normally this isn't a
good idea b/c expressions automatically update themselves when any of their
source column data changes, but while the Expression values available are
pretty accomodating, they aren't unlimited.

HTH,

Bill

How canI get the DataColumn.Expression property handle trigonometric
functions?

For example:
I have a DataTable with 1 columns named "x". I want to add a column that
shows sin(x).

dataset.Tables["trigsample"].Columns.Add("sinx", typeof(double));
dataset.Tables["trigsample"].Columns["sinx"].Expression = "sin(x)";

Any help or ideas you may have are appreciated.

Thanks,

Chris

 

[William Ryan eMVP]

It's still 'possible' it's just not possible using the standard methodology.
If you don't minding doing some slightly high level footwork events , it'll
be 'automatic' to the user. If you are interested, let me know and we'll
get cracking on it.

Bill

www.devbuzz.com
www.knowdotnet.com

Bill,

Thanks for the response. I was hoping to be able to get the automatic
recalculation if the source data changed. I had a feeling this was not
possible. Too bad.

Chris

Hi Chris:

Sin isn't supported by the Expression Syntax. You can do quite a bit and
can probably do it yourself using the available expression

http://msdn.microsoft.com/library/d...fSystemDataDataColumnClassExpressionTopic.asp

but in this instance, you may want to do it on the Sever side or manually
calculate it and add it to the row programatically. Normally this isn't a
good idea b/c expressions automatically update themselves when any of their
source column data changes, but while the Expression values available are
pretty accomodating, they aren't unlimited.

HTH,

Bill

How canI get the DataColumn.Expression property handle trigonometric
functions?

For example:
I have a DataTable with 1 columns named "x". I want to add a column that
shows sin(x).

dataset.Tables["trigsample"].Columns.Add("sinx", typeof(double));
dataset.Tables["trigsample"].Columns["sinx"].Expression = "sin(x)";

Any help or ideas you may have are appreciated.

Thanks,

Chris

 

[Christopher Dedels]

Bill,

Im interested in any suggestions that you may have to solve this problem.
Sounds like fun.

Thanks,

Chris

It's still 'possible' it's just not possible using the standard methodology.
If you don't minding doing some slightly high level footwork events , it'll
be 'automatic' to the user. If you are interested, let me know and we'll
get cracking on it.

Bill

www.devbuzz.com
www.knowdotnet.com

Bill,

Thanks for the response. I was hoping to be able to get the automatic
recalculation if the source data changed. I had a feeling this was not
possible. Too bad.

Chris

http://msdn.microsoft.com/library/d...fSystemDataDataColumnClassExpressionTopic.asp isn't

a

good idea b/c expressions automatically update themselves when any of their
source column data changes, but while the Expression values available are
pretty accomodating, they aren't unlimited.

HTH,

Bill
How canI get the DataColumn.Expression property handle trigonometric
functions?

For example:
I have a DataTable with 1 columns named "x". I want to add a column that
shows sin(x).

dataset.Tables["trigsample"].Columns.Add("sinx", typeof(double));
dataset.Tables["trigsample"].Columns["sinx"].Expression = "sin(x)";

Any help or ideas you may have are appreciated.

Thanks,

Chris

 

[cody]

Why can't you use the ColumnChanged event and Recalculate the value by
yourself?