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Handling DBNull from databasesIf Not row("NetSales") Is DBNull.Value Then NetSales = row("NetSales") End If However, if I use a typed dataset then I can't check for NULL the same way If Not row.NetSales Is DBNull.Value Then NetSales = row.NetSales End If Is there a better way to check for Null values when using typed datasets? Charlie,
AFAIK is the typed dataset from version 1.1 replacing the dbnull values for the normal zero value of the type of value. I don't know it in version 2.0 therefore what version are you using. Cor Show quoteHide quote "Charlie Brown" <cbr***@duclaw.com> schreef in bericht news:1150170432.248638.288340@f6g2000cwb.googlegroups.com... > When checking for NULL values from a database, normally I would use > > If Not row("NetSales") Is DBNull.Value Then > > NetSales = row("NetSales") > > End If > > However, if I use a typed dataset then I can't check for NULL the same > way > > If Not row.NetSales Is DBNull.Value Then > > NetSales = row.NetSales > > End If > > Is there a better way to check for Null values when using typed > datasets? > I am using version 1.1
Regardless of datatype I need to check for NULL values before attempting to assign them to a something else. In a typed dataset values can be NULL when pulled from a database, I would like to leverage benefits of typed datasets in my code. If I use a typed dataset and assign an object a value from that dataset that is null it will throw an exception Dim sngSales as Single = row.Sales I need to check for a NULL value in the Sales column. I can do this by referecing the column like this just fine. If Not row("Sales") is dbNull.Value Then Dim snSales as Single = row.Sales End If But it seems to defeat the benefit of a typed dataset in code. You can't have values in a dataset default to their 'normal' zero values, since 0 and NULL in a financial application are two different things. Cor Ligthert [MVP] wrote: Show quoteHide quote > Charlie, > > AFAIK is the typed dataset from version 1.1 replacing the dbnull values for > the normal zero value of the type of value. I don't know it in version 2.0 > therefore what version are you using. > > Cor > > "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > news:1150170432.248638.288340@f6g2000cwb.googlegroups.com... > > When checking for NULL values from a database, normally I would use > > > > If Not row("NetSales") Is DBNull.Value Then > > > > NetSales = row("NetSales") > > > > End If > > > > However, if I use a typed dataset then I can't check for NULL the same > > way > > > > If Not row.NetSales Is DBNull.Value Then > > > > NetSales = row.NetSales > > > > End If > > > > Is there a better way to check for Null values when using typed > > datasets? > > Charlie,
I can do it for you but better is to do it yourself. If you go to the solution explorer. Click on the button in top show all files, than you can expand the dataset and see the vb code. Just searching on things as dbnull in that will show you how it is handled. Cor Show quoteHide quote "Charlie Brown" <cbr***@duclaw.com> schreef in bericht news:1150204800.112214.203980@g10g2000cwb.googlegroups.com... >I am using version 1.1 > > Regardless of datatype I need to check for NULL values before > attempting to assign them to a something else. In a typed dataset > values can be NULL when pulled from a database, I would like to > leverage benefits of typed datasets in my code. > > If I use a typed dataset and assign an object a value from that dataset > that is null it will throw an exception > > Dim sngSales as Single = row.Sales > > I need to check for a NULL value in the Sales column. I can do this by > referecing the column like this just fine. > > If Not row("Sales") is dbNull.Value Then > Dim snSales as Single = row.Sales > End If > > But it seems to defeat the benefit of a typed dataset in code. You > can't have values in a dataset default to their 'normal' zero values, > since 0 and NULL in a financial application are two different things. > > > Cor Ligthert [MVP] wrote: >> Charlie, >> >> AFAIK is the typed dataset from version 1.1 replacing the dbnull values >> for >> the normal zero value of the type of value. I don't know it in version >> 2.0 >> therefore what version are you using. >> >> Cor >> >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht >> news:1150170432.248638.288340@f6g2000cwb.googlegroups.com... >> > When checking for NULL values from a database, normally I would use >> > >> > If Not row("NetSales") Is DBNull.Value Then >> > >> > NetSales = row("NetSales") >> > >> > End If >> > >> > However, if I use a typed dataset then I can't check for NULL the same >> > way >> > >> > If Not row.NetSales Is DBNull.Value Then >> > >> > NetSales = row.NetSales >> > >> > End If >> > >> > Is there a better way to check for Null values when using typed >> > datasets? >> > > Although I appreciate the advice on how to use my designer, I have
found the answer on my own. For anyone looking, when using typed datasets and checking for DBNULL's the proper way to do so is this... Dim row as TypedDataset.TypedDatasetRow = TypedDataset1.Tables(0).Row(0) Referencing the dataset row this way will allow you to leverage type checking at design time and will create functions belonging to the row object that return a boolean if the data in a column is null. If you have a column named NetSales in your dataset, then the dataset will create an IsNetSalesNull function that returns a boolean value. So the proper way to check for Null values would be the following If Not row.IsNetSalesNull Then Dim sngNetSales as Single = row.NetSales End If Cor Ligthert [MVP] wrote: Show quoteHide quote > Charlie, > > I can do it for you but better is to do it yourself. > > If you go to the solution explorer. Click on the button in top show all > files, than you can expand the dataset and see the vb code. > > Just searching on things as dbnull in that will show you how it is handled. > > Cor > > "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > news:1150204800.112214.203980@g10g2000cwb.googlegroups.com... > >I am using version 1.1 > > > > Regardless of datatype I need to check for NULL values before > > attempting to assign them to a something else. In a typed dataset > > values can be NULL when pulled from a database, I would like to > > leverage benefits of typed datasets in my code. > > > > If I use a typed dataset and assign an object a value from that dataset > > that is null it will throw an exception > > > > Dim sngSales as Single = row.Sales > > > > I need to check for a NULL value in the Sales column. I can do this by > > referecing the column like this just fine. > > > > If Not row("Sales") is dbNull.Value Then > > Dim snSales as Single = row.Sales > > End If > > > > But it seems to defeat the benefit of a typed dataset in code. You > > can't have values in a dataset default to their 'normal' zero values, > > since 0 and NULL in a financial application are two different things. > > > > > > Cor Ligthert [MVP] wrote: > >> Charlie, > >> > >> AFAIK is the typed dataset from version 1.1 replacing the dbnull values > >> for > >> the normal zero value of the type of value. I don't know it in version > >> 2.0 > >> therefore what version are you using. > >> > >> Cor > >> > >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > >> news:1150170432.248638.288340@f6g2000cwb.googlegroups.com... > >> > When checking for NULL values from a database, normally I would use > >> > > >> > If Not row("NetSales") Is DBNull.Value Then > >> > > >> > NetSales = row("NetSales") > >> > > >> > End If > >> > > >> > However, if I use a typed dataset then I can't check for NULL the same > >> > way > >> > > >> > If Not row.NetSales Is DBNull.Value Then > >> > > >> > NetSales = row.NetSales > >> > > >> > End If > >> > > >> > Is there a better way to check for Null values when using typed > >> > datasets? > >> > > > Charlie,
I don't think that this is a good advice. If you had followed what I told you had find something as this in one minute. \\\ Public Property City As String Get Try Return CType(Me(Me.tableEmployees.CityColumn),String) Catch e As InvalidCastException Throw New StrongTypingException("Cannot get value because it is DBNull.", e) End Try End Get Set Me(Me.tableEmployees.CityColumn) = value End Set End Property /// With otherwords catching this exception in a try block when you use this property will give you the needed result in a strongly typed way. I am at the moment only active with version 2005, and that while as most of the regular contributers to dotnet newsgroups do I not like the strongly dataset versions from before 2005. I knew that it was something like this but did not know anymore exactly how. However, because I don't want that other have the wrong answer as the propper way, have I taken some time for this. But that was more easy to do for your if you had taken my advice, I had no project to test this. As I see it well, than you are now just going around the strongly typed dataset by using the non typed part of that. Cor Show quoteHide quote "Charlie Brown" <cbr***@duclaw.com> schreef in bericht news:1150216473.851475.295610@g10g2000cwb.googlegroups.com... > Although I appreciate the advice on how to use my designer, I have > found the answer on my own. For anyone looking, when using typed > datasets and checking for DBNULL's the proper way to do so is this... > > Dim row as TypedDataset.TypedDatasetRow = > TypedDataset1.Tables(0).Row(0) > > Referencing the dataset row this way will allow you to leverage type > checking at design time and will create functions belonging to the row > object that return a boolean if the data in a column is null. > > If you have a column named NetSales in your dataset, then the dataset > will create an IsNetSalesNull function that returns a boolean value. > So the proper way to check for Null values would be the following > > If Not row.IsNetSalesNull Then > Dim sngNetSales as Single = row.NetSales > End If > > Cor Ligthert [MVP] wrote: >> Charlie, >> >> I can do it for you but better is to do it yourself. >> >> If you go to the solution explorer. Click on the button in top show all >> files, than you can expand the dataset and see the vb code. >> >> Just searching on things as dbnull in that will show you how it is >> handled. >> >> Cor >> >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht >> news:1150204800.112214.203980@g10g2000cwb.googlegroups.com... >> >I am using version 1.1 >> > >> > Regardless of datatype I need to check for NULL values before >> > attempting to assign them to a something else. In a typed dataset >> > values can be NULL when pulled from a database, I would like to >> > leverage benefits of typed datasets in my code. >> > >> > If I use a typed dataset and assign an object a value from that dataset >> > that is null it will throw an exception >> > >> > Dim sngSales as Single = row.Sales >> > >> > I need to check for a NULL value in the Sales column. I can do this by >> > referecing the column like this just fine. >> > >> > If Not row("Sales") is dbNull.Value Then >> > Dim snSales as Single = row.Sales >> > End If >> > >> > But it seems to defeat the benefit of a typed dataset in code. You >> > can't have values in a dataset default to their 'normal' zero values, >> > since 0 and NULL in a financial application are two different things. >> > >> > >> > Cor Ligthert [MVP] wrote: >> >> Charlie, >> >> >> >> AFAIK is the typed dataset from version 1.1 replacing the dbnull >> >> values >> >> for >> >> the normal zero value of the type of value. I don't know it in version >> >> 2.0 >> >> therefore what version are you using. >> >> >> >> Cor >> >> >> >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht >> >> news:1150170432.248638.288340@f6g2000cwb.googlegroups.com... >> >> > When checking for NULL values from a database, normally I would use >> >> > >> >> > If Not row("NetSales") Is DBNull.Value Then >> >> > >> >> > NetSales = row("NetSales") >> >> > >> >> > End If >> >> > >> >> > However, if I use a typed dataset then I can't check for NULL the >> >> > same >> >> > way >> >> > >> >> > If Not row.NetSales Is DBNull.Value Then >> >> > >> >> > NetSales = row.NetSales >> >> > >> >> > End If >> >> > >> >> > Is there a better way to check for Null values when using typed >> >> > datasets? >> >> > >> > > I am not going around the strongly typed dataset at all. .net creates
those functions to test for NULL values by itself whenever you create a strong dataset. The reason for using strong datasets is compile time type checking, intellisense, and compact code. I can use the Try catch method as well, but why not check for NULL myself when I know it will be there. I am using the strong type dataset to its full potential. It PROVIDES a way to check for NULL values for a reason. If it didn't provide a way, then a Try Catch block would be more correct. Cor Ligthert [MVP] wrote: Show quoteHide quote > Charlie, > > I don't think that this is a good advice. If you had followed what I told > you had find something as this in one minute. > \\\ > Public Property City As String > Get > Try > Return CType(Me(Me.tableEmployees.CityColumn),String) > Catch e As InvalidCastException > Throw New StrongTypingException("Cannot get value > because it is DBNull.", e) > End Try > End Get > Set > Me(Me.tableEmployees.CityColumn) = value > End Set > End Property > /// > > With otherwords catching this exception in a try block when you use this > property will give you the needed result in a strongly typed way. > > I am at the moment only active with version 2005, and that while as most of > the regular contributers to dotnet newsgroups do I not like the strongly > dataset versions from before 2005. I knew that it was something like this > but did not know anymore exactly how. > > However, because I don't want that other have the wrong answer as the > propper way, have I taken some time for this. But that was more easy to do > for your if you had taken my advice, I had no project to test this. > > As I see it well, than you are now just going around the strongly typed > dataset by using the non typed part of that. > > Cor > > > "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > news:1150216473.851475.295610@g10g2000cwb.googlegroups.com... > > Although I appreciate the advice on how to use my designer, I have > > found the answer on my own. For anyone looking, when using typed > > datasets and checking for DBNULL's the proper way to do so is this... > > > > Dim row as TypedDataset.TypedDatasetRow = > > TypedDataset1.Tables(0).Row(0) > > > > Referencing the dataset row this way will allow you to leverage type > > checking at design time and will create functions belonging to the row > > object that return a boolean if the data in a column is null. > > > > If you have a column named NetSales in your dataset, then the dataset > > will create an IsNetSalesNull function that returns a boolean value. > > So the proper way to check for Null values would be the following > > > > If Not row.IsNetSalesNull Then > > Dim sngNetSales as Single = row.NetSales > > End If > > > > Cor Ligthert [MVP] wrote: > >> Charlie, > >> > >> I can do it for you but better is to do it yourself. > >> > >> If you go to the solution explorer. Click on the button in top show all > >> files, than you can expand the dataset and see the vb code. > >> > >> Just searching on things as dbnull in that will show you how it is > >> handled. > >> > >> Cor > >> > >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > >> news:1150204800.112214.203980@g10g2000cwb.googlegroups.com... > >> >I am using version 1.1 > >> > > >> > Regardless of datatype I need to check for NULL values before > >> > attempting to assign them to a something else. In a typed dataset > >> > values can be NULL when pulled from a database, I would like to > >> > leverage benefits of typed datasets in my code. > >> > > >> > If I use a typed dataset and assign an object a value from that dataset > >> > that is null it will throw an exception > >> > > >> > Dim sngSales as Single = row.Sales > >> > > >> > I need to check for a NULL value in the Sales column. I can do this by > >> > referecing the column like this just fine. > >> > > >> > If Not row("Sales") is dbNull.Value Then > >> > Dim snSales as Single = row.Sales > >> > End If > >> > > >> > But it seems to defeat the benefit of a typed dataset in code. You > >> > can't have values in a dataset default to their 'normal' zero values, > >> > since 0 and NULL in a financial application are two different things. > >> > > >> > > >> > Cor Ligthert [MVP] wrote: > >> >> Charlie, > >> >> > >> >> AFAIK is the typed dataset from version 1.1 replacing the dbnull > >> >> values > >> >> for > >> >> the normal zero value of the type of value. I don't know it in version > >> >> 2.0 > >> >> therefore what version are you using. > >> >> > >> >> Cor > >> >> > >> >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > >> >> news:1150170432.248638.288340@f6g2000cwb.googlegroups.com... > >> >> > When checking for NULL values from a database, normally I would use > >> >> > > >> >> > If Not row("NetSales") Is DBNull.Value Then > >> >> > > >> >> > NetSales = row("NetSales") > >> >> > > >> >> > End If > >> >> > > >> >> > However, if I use a typed dataset then I can't check for NULL the > >> >> > same > >> >> > way > >> >> > > >> >> > If Not row.NetSales Is DBNull.Value Then > >> >> > > >> >> > NetSales = row.NetSales > >> >> > > >> >> > End If > >> >> > > >> >> > Is there a better way to check for Null values when using typed > >> >> > datasets? > >> >> > > >> > > > I am not going around the strongly typed dataset at all. .net creates
those functions to test for NULL values by itself whenever you create a strong dataset. The reason for using strong datasets is compile time type checking, intellisense, and compact code. I can use the Try catch method as well, but why not check for NULL myself when I know it will be there. I am using the strong type dataset to its full potential. It PROVIDES a way to check for NULL values for a reason. If it didn't provide a way, then a Try Catch block would be more correct. Cor Ligthert [MVP] wrote: Show quoteHide quote > Charlie, > > I don't think that this is a good advice. If you had followed what I told > you had find something as this in one minute. > \\\ > Public Property City As String > Get > Try > Return CType(Me(Me.tableEmployees.CityColumn),String) > Catch e As InvalidCastException > Throw New StrongTypingException("Cannot get value > because it is DBNull.", e) > End Try > End Get > Set > Me(Me.tableEmployees.CityColumn) = value > End Set > End Property > /// > > With otherwords catching this exception in a try block when you use this > property will give you the needed result in a strongly typed way. > > I am at the moment only active with version 2005, and that while as most of > the regular contributers to dotnet newsgroups do I not like the strongly > dataset versions from before 2005. I knew that it was something like this > but did not know anymore exactly how. > > However, because I don't want that other have the wrong answer as the > propper way, have I taken some time for this. But that was more easy to do > for your if you had taken my advice, I had no project to test this. > > As I see it well, than you are now just going around the strongly typed > dataset by using the non typed part of that. > > Cor > > > "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > news:1150216473.851475.295610@g10g2000cwb.googlegroups.com... > > Although I appreciate the advice on how to use my designer, I have > > found the answer on my own. For anyone looking, when using typed > > datasets and checking for DBNULL's the proper way to do so is this... > > > > Dim row as TypedDataset.TypedDatasetRow = > > TypedDataset1.Tables(0).Row(0) > > > > Referencing the dataset row this way will allow you to leverage type > > checking at design time and will create functions belonging to the row > > object that return a boolean if the data in a column is null. > > > > If you have a column named NetSales in your dataset, then the dataset > > will create an IsNetSalesNull function that returns a boolean value. > > So the proper way to check for Null values would be the following > > > > If Not row.IsNetSalesNull Then > > Dim sngNetSales as Single = row.NetSales > > End If > > > > Cor Ligthert [MVP] wrote: > >> Charlie, > >> > >> I can do it for you but better is to do it yourself. > >> > >> If you go to the solution explorer. Click on the button in top show all > >> files, than you can expand the dataset and see the vb code. > >> > >> Just searching on things as dbnull in that will show you how it is > >> handled. > >> > >> Cor > >> > >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > >> news:1150204800.112214.203980@g10g2000cwb.googlegroups.com... > >> >I am using version 1.1 > >> > > >> > Regardless of datatype I need to check for NULL values before > >> > attempting to assign them to a something else. In a typed dataset > >> > values can be NULL when pulled from a database, I would like to > >> > leverage benefits of typed datasets in my code. > >> > > >> > If I use a typed dataset and assign an object a value from that dataset > >> > that is null it will throw an exception > >> > > >> > Dim sngSales as Single = row.Sales > >> > > >> > I need to check for a NULL value in the Sales column. I can do this by > >> > referecing the column like this just fine. > >> > > >> > If Not row("Sales") is dbNull.Value Then > >> > Dim snSales as Single = row.Sales > >> > End If > >> > > >> > But it seems to defeat the benefit of a typed dataset in code. You > >> > can't have values in a dataset default to their 'normal' zero values, > >> > since 0 and NULL in a financial application are two different things. > >> > > >> > > >> > Cor Ligthert [MVP] wrote: > >> >> Charlie, > >> >> > >> >> AFAIK is the typed dataset from version 1.1 replacing the dbnull > >> >> values > >> >> for > >> >> the normal zero value of the type of value. I don't know it in version > >> >> 2.0 > >> >> therefore what version are you using. > >> >> > >> >> Cor > >> >> > >> >> "Charlie Brown" <cbr***@duclaw.com> schreef in bericht > >> >> news:1150170432.248638.288340@f6g2000cwb.googlegroups.com... > >> >> > When checking for NULL values from a database, normally I would use > >> >> > > >> >> > If Not row("NetSales") Is DBNull.Value Then > >> >> > > >> >> > NetSales = row("NetSales") > >> >> > > >> >> > End If > >> >> > > >> >> > However, if I use a typed dataset then I can't check for NULL the > >> >> > same > >> >> > way > >> >> > > >> >> > If Not row.NetSales Is DBNull.Value Then > >> >> > > >> >> > NetSales = row.NetSales > >> >> > > >> >> > End If > >> >> > > >> >> > Is there a better way to check for Null values when using typed > >> >> > datasets? > >> >> > > >> > > > 
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