DataColumn.Expression IsNull

[Guest]

Need to return a calculated column in a dataset that indicates whether another column contains a dbnull value. Note this data does not come from any sort of datasource in which I could perform such a calculation.

I initially thought Id be able to use the IsNull function but this appears to be badly named and performs a similar function to Nz within Acces. That is, it is used to convert a value from a null into some default value.

I then thought Id be able to use a combination of isnull & iif, for example

iif(IsNull(myColumn, -1)=-1, -1, 0)

Unluckily since the data type of my column is a number which could contain -1, this wont work too well

Does anyone have any other ideas? Thanks in advance.

 

[William Ryan eMVP]

Badly named? It's pretty much identical to Sql Server's isn't it?

You can still set it to a known value that will conform to the type spec and
then check that with another expression. So a column named Evaluater for
instance could have IsNull(yourColumn, ConformingValue) then another
expression of type int could check for ConformingValue and be 0 or -1
accordingly. AFAIK this should work.

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W.G. Ryan, eMVP

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Need to return a calculated column in a dataset that indicates whether

another column contains a dbnull value. Note this data does not come from
any sort of datasource in which I could perform such a calculation.

I initially thought Id be able to use the IsNull function but this appears

to be badly named and performs a similar function to Nz within Acces. That
is, it is used to convert a value from a null into some default value.

I then thought Id be able to use a combination of isnull & iif, for example

iif(IsNull(myColumn, -1)=-1, -1, 0)

Unluckily since the data type of my column is a number which could

contain -1, this wont work too well

 

[Chitra Krishnan]

Please try this out :
iif(column1 is not null,column1,column2)