CODEWITHSUNDEEP
c#linqcastingdataset
Naila Akbar
Naila Akbar

Reputation: 3358

Difference between DBNull.Value and IsValueNull()

I'm getting some data from Stored Procedure to DataSet and then copying that data to a List. There are some NULL values in data and for that I'm checking with DBNULL.Value. But whenever it comes to a NULL value, it gives me error

ERROR : Specified cast is not valid.

This is how I'm copying data from DataSet to List.

AreaId = dsTable.SearchedTable[I]["AreaId"] == DBNULL.Value ? 0 : (long)dsTable.SearchedTable[I]["AreaId"];

Sometimes it works fine but sometimes it gives me error.

And when I change this DBNULL.Value to IsAreaIdNull(). It works fine.

AreaId = dsTable.SearchedTable[I].IsAreaIdNull() ? 0 : (long)dsTable.SearchedTable[I]["AreaId"];

I'm confused that what's wrong with DBNull.Value because it is working perfectly fine in other procedures. Even in same procedure for other values. M i missing something in it??

Any kind of help will be appreciated.

Upvotes: 1

Views: 66

Answers (1)

Andrey Korneyev
Andrey Korneyev

Reputation: 26886

It looks like you have a typo: assignment instead of equality comparison here:

dsTable.SearchedTable[I]["AreaId"] = DBNULL.Value ? 0 : 
                                                   (long)dsTable.SearchedTable[I]["AreaId"];

It should be 

dsTable.SearchedTable[I]["AreaId"] == DBNULL.Value ? 0 : 
                                                    (long)dsTable.SearchedTable[I]["AreaId"];

Upvotes: 2

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