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dotnet xml : Null elements don't appear in XMLTextWriter results
"AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message news:19rAc.4611$fd.133@twister.socal.rr.com... > I am running the code below to generate XML from a data table. But some > fields in the data table are Null for every record. Suppose field5 has a > null database value. I would expect to see: > > <field5></field5> or <field5 /> > > but instead it doesn't even show the field at all for those records where > field5 is Null! Instead it just shows: > > <field4>Whatever</field4> > <field6>Whatever</field6> > > This concerns me because if people take XML file output and import into a > database, they won't even know field5 exists unless some of the records have > a non null value. But sometimes field5 is null in all records. So how do > I get the writer to make an empty <field5 /> representation so database > imports won't get screwed up? .... [quoted text, click to view] > Here's my code: Here's mine: Public Shared Function GetXML(ByVal dtDataTable As DataTable, ByVal xwXmlTextWriter As XmlTextWriter) As String If dtDataTable Is Nothing Then Throw New Exception("DataTable cannot be nothing") ' Should really use ApplicationException End If 'End of If objDataTable Is Nothing Then Dim intCounter As Int32 xwXmlTextWriter.WriteStartElement(dtDataTable.TableName) Dim row As DataRow For Each row In dtDataTable.Rows xwXmlTextWriter.WriteStartElement("Row") Dim col As DataColumn For Each col In dtDataTable.Columns xwXmlTextWriter.WriteElementString(col.ColumnName, row(col).ToString()) Next xwXmlTextWriter.WriteEndElement() Next xwXmlTextWriter.WriteEndElement() Return xwXmlTextWriter.ToString() End Function Some comments: 1) If you're going to prefix variables with a type abbreviation, I recommend against using "obj". Everything is an object, so that doesn't tell you anything. 2) I generally use "For Each" loops instead of using an index unless I need to use the index within the loop. The index is just an artifact of the fact that you're looping. 3) You don't have to use ToString on strings. col.ColumnName is already a string. -- John Saunders johnwsaundersiii at hotmail
I am running the code below to generate XML from a data table. But some
fields in the data table are Null for every record. Suppose field5 has a null database value. I would expect to see: <field5></field5> or <field5 /> but instead it doesn't even show the field at all for those records where field5 is Null! Instead it just shows: <field4>Whatever</field4> <field6>Whatever</field6> This concerns me because if people take XML file output and import into a database, they won't even know field5 exists unless some of the records have a non null value. But sometimes field5 is null in all records. So how do I get the writer to make an empty <field5 /> representation so database imports won't get screwed up? On a side note, where would I flush the buffer in my code below? Here's my code: Public Shared Function GetXML(ByVal objDataTable As DataTable, ByVal objXmlTextWriter As XmlTextWriter) As String If IsNothing(objDataTable) Then Throw New Exception("DataTable cannot be nothing") End If 'End of If Not Nothing(objDataTable) Then Dim intCounter As Int32 objXmlTextWriter.WriteStartElement(objDataTable.TableName) For intCounter = 0 To objDataTable.Rows.Count - 1 objXmlTextWriter.WriteStartElement("Row") Dim objDataColumn As DataColumn For Each objDataColumn In objDataTable.Columns objXmlTextWriter.WriteElementString(objDataColumn.ColumnName.ToString(), objDataTable.Rows(intCounter).Item(objDataColumn.ColumnName).ToString()) Next objXmlTextWriter.WriteEndElement() Next objXmlTextWriter.WriteEndElement() Return objXmlTextWriter.ToString End Function
[quoted text, click to view] "John Saunders" <johnwsaundersiii@notcoldmail.com> wrote in message news:um3Y2cNVEHA.3656@TK2MSFTNGP11.phx.gbl... > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > news:19rAc.4611$fd.133@twister.socal.rr.com... > > I am running the code below to generate XML from a data table. But some > > fields in the data table are Null for every record. Suppose field5 has a > > null database value. I would expect to see: > > > > <field5></field5> or <field5 /> > > > > but instead it doesn't even show the field at all for those records where > > field5 is Null! Instead it just shows: > > > > <field4>Whatever</field4> > > <field6>Whatever</field6> > > > > This concerns me because if people take XML file output and import into a > > database, they won't even know field5 exists unless some of the records > have > > a non null value. But sometimes field5 is null in all records. So how > do > > I get the writer to make an empty <field5 /> representation so database > > imports won't get screwed up? > > ... > > > Here's my code: > > Here's mine: > > Public Shared Function GetXML(ByVal dtDataTable As DataTable, ByVal > xwXmlTextWriter As XmlTextWriter) As String > If dtDataTable Is Nothing Then > Throw New Exception("DataTable cannot be nothing") ' Should > really use ApplicationException > End If 'End of If objDataTable Is Nothing Then > > Dim intCounter As Int32 > > xwXmlTextWriter.WriteStartElement(dtDataTable.TableName) > > Dim row As DataRow > For Each row In dtDataTable.Rows > xwXmlTextWriter.WriteStartElement("Row") > Dim col As DataColumn > For Each col In dtDataTable.Columns > xwXmlTextWriter.WriteElementString(col.ColumnName, > row(col).ToString()) > Next > xwXmlTextWriter.WriteEndElement() > Next > > xwXmlTextWriter.WriteEndElement() > > Return xwXmlTextWriter.ToString() > End Function > > Some comments: > > 1) If you're going to prefix variables with a type abbreviation, I recommend > against using "obj". Everything is an object, so that doesn't tell you > anything. > 2) I generally use "For Each" loops instead of using an index unless I need > to use the index within the loop. The index is just an artifact of the fact > that you're looping. > 3) You don't have to use ToString on strings. col.ColumnName is already a > string. > > -- > John Saunders > johnwsaundersiii at hotmail > > I appreciate your code suggestions. Thanks. I did not write the function and you are absolutely correct. BUT, it still doesn't solve my #1 problem of a missing <field5 /> when field5 is null. Do you know how can I fix this?
[quoted text, click to view] "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message news:vesAc.4613$fd.1134@twister.socal.rr.com... > > "John Saunders" <johnwsaundersiii@notcoldmail.com> wrote in message > news:um3Y2cNVEHA.3656@TK2MSFTNGP11.phx.gbl... > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > > news:19rAc.4611$fd.133@twister.socal.rr.com... > > > I am running the code below to generate XML from a data table. But > some > > > fields in the data table are Null for every record. Suppose field5 has > a > > > null database value. I would expect to see: > > > > > > <field5></field5> or <field5 /> > > > > > > but instead it doesn't even show the field at all for those records > where > > > field5 is Null! Instead it just shows: > > > > > > <field4>Whatever</field4> > > > <field6>Whatever</field6> > > > > > > This concerns me because if people take XML file output and import into > a > > > database, they won't even know field5 exists unless some of the records > > have > > > a non null value. But sometimes field5 is null in all records. So > how > > do > > > I get the writer to make an empty <field5 /> representation so database > > > imports won't get screwed up? > > > > ... > > > > > Here's my code: > > > > Here's mine: > > > > Public Shared Function GetXML(ByVal dtDataTable As DataTable, ByVal > > xwXmlTextWriter As XmlTextWriter) As String > > If dtDataTable Is Nothing Then > > Throw New Exception("DataTable cannot be nothing") ' Should > > really use ApplicationException > > End If 'End of If objDataTable Is Nothing Then > > > > Dim intCounter As Int32 > > > > xwXmlTextWriter.WriteStartElement(dtDataTable.TableName) > > > > Dim row As DataRow > > For Each row In dtDataTable.Rows > > xwXmlTextWriter.WriteStartElement("Row") > > Dim col As DataColumn > > For Each col In dtDataTable.Columns > > xwXmlTextWriter.WriteElementString(col.ColumnName, > > row(col).ToString()) > > Next > > xwXmlTextWriter.WriteEndElement() > > Next > > > > xwXmlTextWriter.WriteEndElement() > > > > Return xwXmlTextWriter.ToString() > > End Function > > > > Some comments: > > > > 1) If you're going to prefix variables with a type abbreviation, I > recommend > > against using "obj". Everything is an object, so that doesn't tell you > > anything. > > 2) I generally use "For Each" loops instead of using an index unless I > need > > to use the index within the loop. The index is just an artifact of the > fact > > that you're looping. > > 3) You don't have to use ToString on strings. col.ColumnName is already a > > string. > > > > -- > > John Saunders > > johnwsaundersiii at hotmail > > > > > > > > I appreciate your code suggestions. Thanks. I did not write the function > and you are absolutely correct. > > BUT, it still doesn't solve my #1 problem of a missing <field5 /> when > field5 is null. Do you know how can I fix this? > > I just realized that the previous programmer was calling the .net framework's DataSet.GetXML() method instead of this custom function I posted. Duh!!! My function does correctly show <field5 />. But does anyone know why the built-in framework GetXML method does NOT show empty elements? Also, can anyone still comment on how I would empty the buffer in my code? I don't understand that but I read that you should do that. I don't know where in the code and how.
[quoted text, click to view]
"AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message news:iHsAc.4617$fd.3771@twister.socal.rr.com... > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > news:vesAc.4613$fd.1134@twister.socal.rr.com... > > > > "John Saunders" <johnwsaundersiii@notcoldmail.com> wrote in message > > news:um3Y2cNVEHA.3656@TK2MSFTNGP11.phx.gbl... > > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > > > news:19rAc.4611$fd.133@twister.socal.rr.com... > > > > I am running the code below to generate XML from a data table. But > > some > > > > fields in the data table are Null for every record. Suppose field5 > has > > a > > > > null database value. I would expect to see: > > > > > > > > <field5></field5> or <field5 /> > > > > > > > > but instead it doesn't even show the field at all for those records > > where > > > > field5 is Null! Instead it just shows: > > > > > > > > <field4>Whatever</field4> > > > > <field6>Whatever</field6> > > > > > > > > This concerns me because if people take XML file output and import > into > > a > > > > database, they won't even know field5 exists unless some of the > records > > > have > > > > a non null value. But sometimes field5 is null in all records. So > > how > > > do > > > > I get the writer to make an empty <field5 /> representation so > database > > > > imports won't get screwed up? > > > > > > ... > > > > > > > Here's my code: > > > > > > Here's mine: > > > > > > Public Shared Function GetXML(ByVal dtDataTable As DataTable, ByVal > > > xwXmlTextWriter As XmlTextWriter) As String > > > If dtDataTable Is Nothing Then > > > Throw New Exception("DataTable cannot be nothing") ' Should > > > really use ApplicationException > > > End If 'End of If objDataTable Is Nothing Then > > > > > > Dim intCounter As Int32 > > > > > > xwXmlTextWriter.WriteStartElement(dtDataTable.TableName) > > > > > > Dim row As DataRow > > > For Each row In dtDataTable.Rows > > > xwXmlTextWriter.WriteStartElement("Row") > > > Dim col As DataColumn > > > For Each col In dtDataTable.Columns > > > xwXmlTextWriter.WriteElementString(col.ColumnName, > > > row(col).ToString()) > > > Next > > > xwXmlTextWriter.WriteEndElement() > > > Next > > > > > > xwXmlTextWriter.WriteEndElement() > > > > > > Return xwXmlTextWriter.ToString() > > > End Function > > > > > > Some comments: > > > > > > 1) If you're going to prefix variables with a type abbreviation, I > > recommend > > > against using "obj". Everything is an object, so that doesn't tell you > > > anything. > > > 2) I generally use "For Each" loops instead of using an index unless I > > need > > > to use the index within the loop. The index is just an artifact of the > > fact > > > that you're looping. > > > 3) You don't have to use ToString on strings. col.ColumnName is already > a > > > string. > > > > > > -- > > > John Saunders > > > johnwsaundersiii at hotmail > > > > > > > > > > > > > > I appreciate your code suggestions. Thanks. I did not write the function > > and you are absolutely correct. > > > > BUT, it still doesn't solve my #1 problem of a missing <field5 /> when > > field5 is null. Do you know how can I fix this? > > > > > > > > I just realized that the previous programmer was calling the .net > framework's DataSet.GetXML() method instead of this custom function I > posted. Duh!!! My function does correctly show <field5 />. But does > anyone know why the built-in framework GetXML method does NOT show empty > elements? Why should it show empty elements? NULL in SQL doesn't mean empty, it means not present or "I don't know". [quoted text, click to view] > Also, can anyone still comment on how I would empty the buffer in my code? > I don't understand that but I read that you should do that. I don't know > where in the code and how. I don't see that you should "empty the buffer". The XmlWriter.ToString() at the end will return the string representation of all the XML elements you've written to it. -- John Saunders johnwsaundersiii at hotmail
[quoted text, click to view]
"AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message news:TzEAc.5940$fd.2386@twister.socal.rr.com... > > "John Saunders" <johnwsaundersiii@notcoldmail.com> wrote in message > news:%23xyl0NSVEHA.3988@tk2msftngp13.phx.gbl... > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > > news:iHsAc.4617$fd.3771@twister.socal.rr.com... > > > > > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > > > news:vesAc.4613$fd.1134@twister.socal.rr.com... > > > > > > > > "John Saunders" <johnwsaundersiii@notcoldmail.com> wrote in message > > > > news:um3Y2cNVEHA.3656@TK2MSFTNGP11.phx.gbl... > > > > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > > > > > news:19rAc.4611$fd.133@twister.socal.rr.com... > > > > > > I am running the code below to generate XML from a data table. > But > > > > some > > > > > > fields in the data table are Null for every record. Suppose > field5 > > > has > > > > a > > > > > > null database value. I would expect to see: > > > > > > > > > > > > <field5></field5> or <field5 /> > > > > > > > > > > > > but instead it doesn't even show the field at all for those > records > > > > where > > > > > > field5 is Null! Instead it just shows: > > > > > > > > > > > > <field4>Whatever</field4> > > > > > > <field6>Whatever</field6> > > > > > > > > > > > > This concerns me because if people take XML file output and import > > > into > > > > a > > > > > > database, they won't even know field5 exists unless some of the > > > records > > > > > have > > > > > > a non null value. But sometimes field5 is null in all records. > > So > > > > how > > > > > do > > > > > > I get the writer to make an empty <field5 /> representation so > > > database > > > > > > imports won't get screwed up? > > > > > > > > > > ... > > > > > > > > > > > Here's my code: > > > > > > > > > > Here's mine: > > > > > > > > > > Public Shared Function GetXML(ByVal dtDataTable As DataTable, > > ByVal > > > > > xwXmlTextWriter As XmlTextWriter) As String > > > > > If dtDataTable Is Nothing Then > > > > > Throw New Exception("DataTable cannot be nothing") ' > > Should > > > > > really use ApplicationException > > > > > End If 'End of If objDataTable Is Nothing Then > > > > > > > > > > Dim intCounter As Int32 > > > > > > > > > > xwXmlTextWriter.WriteStartElement(dtDataTable.TableName) > > > > > > > > > > Dim row As DataRow > > > > > For Each row In dtDataTable.Rows > > > > > xwXmlTextWriter.WriteStartElement("Row") > > > > > Dim col As DataColumn > > > > > For Each col In dtDataTable.Columns > > > > > xwXmlTextWriter.WriteElementString(col.ColumnName, > > > > > row(col).ToString()) > > > > > Next > > > > > xwXmlTextWriter.WriteEndElement() > > > > > Next > > > > > > > > > > xwXmlTextWriter.WriteEndElement() > > > > > > > > > > Return xwXmlTextWriter.ToString() > > > > > End Function > > > > > > > > > > Some comments: > > > > > > > > > > 1) If you're going to prefix variables with a type abbreviation, I > > > > recommend > > > > > against using "obj". Everything is an object, so that doesn't tell > you > > > > > anything. > > > > > 2) I generally use "For Each" loops instead of using an index unless > I > > > > need > > > > > to use the index within the loop. The index is just an artifact of > the > > > > fact > > > > > that you're looping. > > > > > 3) You don't have to use ToString on strings. col.ColumnName is > > already > > > a > > > > > string. > > > > > > > > > > -- > > > > > John Saunders > > > > > johnwsaundersiii at hotmail > > > > > > > > > > > > > > > > > > > > > > > > > > I appreciate your code suggestions. Thanks. I did not write the > > function > > > > and you are absolutely correct. > > > > > > > > BUT, it still doesn't solve my #1 problem of a missing <field5 /> when > > > > field5 is null. Do you know how can I fix this? > > > > > > > > > > > > > > > > > > > > I just realized that the previous programmer was calling the .net > > > framework's DataSet.GetXML() method instead of this custom function I > > > posted. Duh!!! My function does correctly show <field5 />. But > does > > > anyone know why the built-in framework GetXML method does NOT show empty > > > elements? > > > > Why should it show empty elements? NULL in SQL doesn't mean empty, it > means > > not present or "I don't know". > > > > > Also, can anyone still comment on how I would empty the buffer in my > code? > > > I don't understand that but I read that you should do that. I don't > know > > > where in the code and how. > > > > I don't see that you should "empty the buffer". The XmlWriter.ToString() > at > > the end will return the string representation of all the XML elements > you've > > written to it. > > -- > > John Saunders > > johnwsaundersiii at hotmail > > > > > > > > It should show empty elements, IMO, to maintain the structure of the XML, so > that importing programs know that the field exists with a NULL value. > Otherwise, if field5 had Nulls in every record, in my example above, there > would be no <field5> reference anywhere in the XML and no importing program > would know of that field name. > > Thanks for your reply again. In that case, there should be two parts to the XML. One should be the schema, which would indicate all of the fields possible in the data. The other would be the data itself, which would have no entries for NULL fields. -- John Saunders johnwsaundersiii at hotmail
[quoted text, click to view] "John Saunders" <johnwsaundersiii@notcoldmail.com> wrote in message news:%23xyl0NSVEHA.3988@tk2msftngp13.phx.gbl... > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > news:iHsAc.4617$fd.3771@twister.socal.rr.com... > > > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > > news:vesAc.4613$fd.1134@twister.socal.rr.com... > > > > > > "John Saunders" <johnwsaundersiii@notcoldmail.com> wrote in message > > > news:um3Y2cNVEHA.3656@TK2MSFTNGP11.phx.gbl... > > > > "AFN" <DELETEnewsgroupCAPSaccount@yahoo.com> wrote in message > > > > news:19rAc.4611$fd.133@twister.socal.rr.com... > > > > > I am running the code below to generate XML from a data table. But > > > some > > > > > fields in the data table are Null for every record. Suppose field5 > > has > > > a > > > > > null database value. I would expect to see: > > > > > > > > > > <field5></field5> or <field5 /> > > > > > > > > > > but instead it doesn't even show the field at all for those records > > > where > > > > > field5 is Null! Instead it just shows: > > > > > > > > > > <field4>Whatever</field4> > > > > > <field6>Whatever</field6> > > > > > > > > > > This concerns me because if people take XML file output and import > > into > > > a > > > > > database, they won't even know field5 exists unless some of the > > records > > > > have > > > > > a non null value. But sometimes field5 is null in all records. > So > > > how > > > > do > > > > > I get the writer to make an empty <field5 /> representation so > > database > > > > > imports won't get screwed up? > > > > > > > > ... > > > > > > > > > Here's my code: > > > > > > > > Here's mine: > > > > > > > > Public Shared Function GetXML(ByVal dtDataTable As DataTable, > ByVal > > > > xwXmlTextWriter As XmlTextWriter) As String > > > > If dtDataTable Is Nothing Then > > > > Throw New Exception("DataTable cannot be nothing") ' > Should > > > > really use ApplicationException > > > > End If 'End of If objDataTable Is Nothing Then > > > > > > > > Dim intCounter As Int32 > > > > > > > > xwXmlTextWriter.WriteStartElement(dtDataTable.TableName) > > > > > > > > Dim row As DataRow > > > > For Each row In dtDataTable.Rows > > > > xwXmlTextWriter.WriteStartElement("Row") > > > > Dim col As DataColumn > > > > For Each col In dtDataTable.Columns > > > > xwXmlTextWriter.WriteElementString(col.ColumnName, > > > > row(col).ToString()) > > > > Next > > > > xwXmlTextWriter.WriteEndElement() > > > > Next > > > > > > > > xwXmlTextWriter.WriteEndElement() > > > > > > > > Return xwXmlTextWriter.ToString() > > > > End Function > > > > > > > > Some comments: > > > > > > > > 1) If you're going to prefix variables with a type abbreviation, I > > > recommend > > > > against using "obj". Everything is an object, so that doesn't tell you > > > > anything. > > > > 2) I generally use "For Each" loops instead of using an index unless I > > > need > > > > to use the index within the loop. The index is just an artifact of the > > > fact > > > > that you're looping. > > > > 3) You don't have to use ToString on strings. col.ColumnName is > already > > a > > > > string. > > > > > > > > -- > > > > John Saunders > > > > johnwsaundersiii at hotmail > > > > > > > > > > > > > > > > > > > > I appreciate your code suggestions. Thanks. I did not write the > function > > > and you are absolutely correct. > > > > > > BUT, it still doesn't solve my #1 problem of a missing <field5 /> when > > > field5 is null. Do you know how can I fix this? > > > > > > > > > > > > > > I just realized that the previous programmer was calling the .net > > framework's DataSet.GetXML() method instead of this custom function I > > posted. Duh!!! My function does correctly show <field5 />. But does > > anyone know why the built-in framework GetXML method does NOT show empty > > elements? > > Why should it show empty elements? NULL in SQL doesn't mean empty, it means > not present or "I don't know". > > > Also, can anyone still comment on how I would empty the buffer in my code? > > I don't understand that but I read that you should do that. I don't know > > where in the code and how. > > I don't see that you should "empty the buffer". The XmlWriter.ToString() at > the end will return the string representation of all the XML elements you've > written to it. > -- > John Saunders > johnwsaundersiii at hotmail > > It should show empty elements, IMO, to maintain the structure of the XML, so that importing programs know that the field exists with a NULL value. Otherwise, if field5 had Nulls in every record, in my example above, there would be no <field5> reference anywhere in the XML and no importing program would know of that field name. Thanks for your reply again.
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