> I am having a problem using Multidim arrays.  I want to create an array
> which as I understand it is dimensioned as:
>
> dim xyz (rows,columns) as String
>
> I want to populate it with rows from a table in a database.  I don't know
> how many rows I am getting so of course I have to Redim inside the loop that
> does this.
>
> Unfortunately, the error message and documentation say: "In a
> multidimensional array, you can change only the last dimension when you use
> Preserve"
>
> How can that be?  How can you not be able to change the number of rows?  Or
> am I missing something?  Is there a different variable type that I need to
> use?
>
> Thanx in advance,
> --
> Anil Gupte
> www.keeninc.net
> www.icinema.com

"rowe_newsgroups" <rowe_em***@yahoo.com> wrote in message
news:1160045446.803957.323040@m7g2000cwm.googlegroups.com...
>> Is there a different variable type that I need to use?
>
> Use a dataset for working with database tables.
>
> Also you could build a dynamic array by first counting the number of
> rows and columns, then sizing the array, and then populating it. But
> that will give you a difficult to manage, unflexible,  memory hog of an
> object, so you should stick with the datasets.
>
> Thanks,
>
> Seth Rowe
>
> Anil Gupte wrote:
>> I am having a problem using Multidim arrays.  I want to create an array
>> which as I understand it is dimensioned as:
>>
>> dim xyz (rows,columns) as String
>>
>> I want to populate it with rows from a table in a database.  I don't know
>> how many rows I am getting so of course I have to Redim inside the loop
>> that
>> does this.
>>
>> Unfortunately, the error message and documentation say: "In a
>> multidimensional array, you can change only the last dimension when you
>> use
>> Preserve"
>>
>> How can that be?  How can you not be able to change the number of rows?
>> Or
>> am I missing something?  Is there a different variable type that I need
>> to
>> use?
>>
>> Thanx in advance,
>> --
>> Anil Gupte
>> www.keeninc.net
>> www.icinema.com
>

> Well, two things here.  Not allowing the number of rows to change is the
> dmbest implementation of Arrays I have ever seen.  I'd like to thump the guy
> in charge of that piece. :-)
>
> But more pertinently, lests discuss your suggestion of using datasets.  I
> already am using a dataset.  I am trying to put the data from the dataset
> into an array so I can access it more easily.  The underlying problem is
> that I have a dropdown list where based on the selection I want to access
> another table.  So, for example, if I have:
>
> One
> Two
> Three
> Four
>
> in a drop down list that comes from a table (call it Table1) containing
> One, Kids
> Two, Adults
> Three, Couples
> Four, Singles
>
> I want to then select from a different table based on the drop down
> selection.  So if someone chooses Kids from the drop down, I want to execute
> "Select * from Table2 where xyz='Kids'"
>
> Any suggestions?
> --
> Anil Gupte
> www.keeninc.net
> www.icinema.com
>
> "rowe_newsgroups" <rowe_em***@yahoo.com> wrote in message
> news:1160045446.803957.323040@m7g2000cwm.googlegroups.com...
> >> Is there a different variable type that I need to use?
> >
> > Use a dataset for working with database tables.
> >
> > Also you could build a dynamic array by first counting the number of
> > rows and columns, then sizing the array, and then populating it. But
> > that will give you a difficult to manage, unflexible,  memory hog of an
> > object, so you should stick with the datasets.
> >
> > Thanks,
> >
> > Seth Rowe
> >
> > Anil Gupte wrote:
> >> I am having a problem using Multidim arrays.  I want to create an array
> >> which as I understand it is dimensioned as:
> >>
> >> dim xyz (rows,columns) as String
> >>
> >> I want to populate it with rows from a table in a database.  I don't know
> >> how many rows I am getting so of course I have to Redim inside the loop
> >> that
> >> does this.
> >>
> >> Unfortunately, the error message and documentation say: "In a
> >> multidimensional array, you can change only the last dimension when you
> >> use
> >> Preserve"
> >>
> >> How can that be?  How can you not be able to change the number of rows?
> >> Or
> >> am I missing something?  Is there a different variable type that I need
> >> to
> >> use?
> >>
> >> Thanx in advance,
> >> --
> >> Anil Gupte
> >> www.keeninc.net
> >> www.icinema.com
> >

"rowe_newsgroups" <rowe_em***@yahoo.com> wrote in message
news:1160230749.943349.155630@i42g2000cwa.googlegroups.com...
>> Well, two things here.  Not allowing the number of rows to change is the
>> dmbest implementation of Arrays I have ever seen.  I'd like to thump the
>> guy
>> in charge of that piece. :-)
>
> If you really wanted to, you could create your own methods to resize an
> array. You would just have to create a new array with the correct
> number or rows and columns. Then loop through the original array
> plugging these values into the proper place in the new array. But then
> you might as well flush the scalability and performance of your app
> down the toilet :-)
>
>> I want to then select from a different table based on the drop down
>> selection.  So if someone chooses Kids from the drop down, I want to
>> execute
>> "Select * from Table2 where xyz='Kids'"
>
> When the user changes the selection of the drop down list, why not just
> hit one of the dataset tables with the SQL command? Also, you could
> just use datareaders to populate the drop down and then execute your
> SQL commands directly against the server. This may be better if you
> have data that constantly changes, as you won't have to worry about
> refreshing the dataset all the time. Also, as a small warning, building
> SQL commands "on the fly" can be prone to SQL injection attacks, you
> may look into using parameterized Stored procedures (or whatever
> alternitive your database provides) in order to protect against these
> attacks.
>
> Hope that Helps,
>
> Seth Rowe
>
> Anil Gupte wrote:
>> Well, two things here.  Not allowing the number of rows to change is the
>> dmbest implementation of Arrays I have ever seen.  I'd like to thump the
>> guy
>> in charge of that piece. :-)
>>
>> But more pertinently, lests discuss your suggestion of using datasets.  I
>> already am using a dataset.  I am trying to put the data from the dataset
>> into an array so I can access it more easily.  The underlying problem is
>> that I have a dropdown list where based on the selection I want to access
>> another table.  So, for example, if I have:
>>
>> One
>> Two
>> Three
>> Four
>>
>> in a drop down list that comes from a table (call it Table1) containing
>> One, Kids
>> Two, Adults
>> Three, Couples
>> Four, Singles
>>
>> I want to then select from a different table based on the drop down
>> selection.  So if someone chooses Kids from the drop down, I want to
>> execute
>> "Select * from Table2 where xyz='Kids'"
>>
>> Any suggestions?
>> --
>> Anil Gupte
>> www.keeninc.net
>> www.icinema.com
>>
>> "rowe_newsgroups" <rowe_em***@yahoo.com> wrote in message
>> news:1160045446.803957.323040@m7g2000cwm.googlegroups.com...
>> >> Is there a different variable type that I need to use?
>> >
>> > Use a dataset for working with database tables.
>> >
>> > Also you could build a dynamic array by first counting the number of
>> > rows and columns, then sizing the array, and then populating it. But
>> > that will give you a difficult to manage, unflexible,  memory hog of an
>> > object, so you should stick with the datasets.
>> >
>> > Thanks,
>> >
>> > Seth Rowe
>> >
>> > Anil Gupte wrote:
>> >> I am having a problem using Multidim arrays.  I want to create an
>> >> array
>> >> which as I understand it is dimensioned as:
>> >>
>> >> dim xyz (rows,columns) as String
>> >>
>> >> I want to populate it with rows from a table in a database.  I don't
>> >> know
>> >> how many rows I am getting so of course I have to Redim inside the
>> >> loop
>> >> that
>> >> does this.
>> >>
>> >> Unfortunately, the error message and documentation say: "In a
>> >> multidimensional array, you can change only the last dimension when
>> >> you
>> >> use
>> >> Preserve"
>> >>
>> >> How can that be?  How can you not be able to change the number of
>> >> rows?
>> >> Or
>> >> am I missing something?  Is there a different variable type that I
>> >> need
>> >> to
>> >> use?
>> >>
>> >> Thanx in advance,
>> >> --
>> >> Anil Gupte
>> >> www.keeninc.net
>> >> www.icinema.com
>> >
>

"Branco Medeiros" <branco.medei***@gmail.com> wrote in message
news:1160210476.440386.162810@m7g2000cwm.googlegroups.com...
> Anil Gupte wrote:
>> I am having a problem using Multidim arrays.  I want to create an array
>> which as I understand it is dimensioned as:
>>
>> dim xyz (rows,columns) as String
>>
>> I want to populate it with rows from a table in a database.  I don't know
>> how many rows I am getting so of course I have to Redim inside the loop
>> that
>> does this.
>>
>> Unfortunately, the error message and documentation say: "In a
>> multidimensional array, you can change only the last dimension when you
>> use
>> Preserve"
> <snip>
>
> You must declare your array like this:
>
>  Dim xyz(Columns, Rows) As String
>
> This way the Rows dimmension can be resized at will.
>
> The Redim keyword comes from VB.Classic. It turns out that arrays, in
> VB.Classic, used column-major order (maybe because Basic copied so many
> Fortran features). This means that the array binaries were layed out in
> memory in a way that turned impractical to redim any but the last
> dimmension. For instance, the following array:
>
>  Dim A(0 To 1, 0 To 2) As Integer
>
> Would have the following layout in memory in VB.Classic:
>
>  (0,0) (1, 0) (0, 1) (1, 1) (0, 2) (1, 2)
>
> As you can see, resizing the first dimmension would require introducing
> gaps all over the array, something doable but expensive. On the other
> hand, resizing the last dimmension would only allocate more space at
> the end of the array.
>
> Notice that arrays in .Net have Row.major order. This means that the
> previous array, in .Net, is layed out in memory like this:
>
>  (0, 0) (0, 1) (0, 2) (1, 0) (1, 1) (1, 2)
>
> which makes easier to resize the first dimmension, but not the others.
>
> Nevertheless, the Redim rule from VB.Classic still applies, because of
> compatibility issues. The irony is that VB.Net must now perform a
> costly "copy by chunks" operation when you redim the array... :-P
>
>
> HTH.
>
> Regards,
>
> Branco.
>

"Branco Medeiros" <branco.medei***@gmail.com> wrote in message
news:1160256362.213911.60470@e3g2000cwe.googlegroups.com...
> Anil Gupte wrote:
> <snip>
>> Anyway, I did not underatand your statement:
>>
>> Dim xyz(Columns, Rows) As String
>>
>> Do you actually use the words Columns and Rows?  I am doing:
>> Dim xyz(,) As String
> <snip>
>
> Sorry, I didn't make it clear. What I meant was to treat the first
> dimmension as the column selector, and the last dimmension as the row
> selector. So, if you have a table with the columns "Name" and "Age",
> you'd have:
>
>  Dim Items(0 To 1, 0 To -1) As String 'An empty table
>
>  '...
>  'Adds a row:
>  Dim NewIndex As Integer = Items.GetLength(1)
>  Redim Preserve Items(0 To 1, 0 To NewIndex)
>  Items(0, NewIndex) = TheName
>  Items(1, NewIndex) = TheAge
>
> Of course, all this trouble is because you want to extract the data
> from the original dataset.
> Another approach could be to use the orginal table:
>
>    mData = New DataTable
>
>    mData.Columns.Add("ID", GetType(Integer), Nothing)
>    mData.Columns.Add("Name", GetType(String), Nothing)
>    mData.Columns.Add("DisplayText", _
>      GetType(String), "id + ' - ' + name")
>
>    mData.Rows.Add(1, "John")
>    mData.Rows.Add(2, "Mary")
>    mData.Rows.Add(3, "Lamb")
>    mData.Rows.Add(4, "Little Pig")
>
>    With Me.ComboBox1
>      .DataSource = mData
>      .DisplayMember = "DisplayText"
>      .ValueMember = "ID"
>
>      'Selects the item with ID = 4
>      .SelectedValue = 4
>    End With
>
> HTH
>
> Regards,
>
> Branco.
>

"Anil Gupte" <anil-l***@icinema.com> wrote in message
news:ebHR%23$p6GHA.4232@TK2MSFTNGP02.phx.gbl...
> Thanx for the help.  I got it working with the dataset instead of using
> the arrays.  However, now I have different problem.  The
> DropDownProfiles.SelectedValue returns a "DataRowView" instead of the
> value from the field (my program expects an integer).  If you have some
> suggestions, let me know.
>
> Thanx for the help so far.
> --
> Anil Gupte
> www.keeninc.net
> www.icinema.com
>
> "Branco Medeiros" <branco.medei***@gmail.com> wrote in message
> news:1160256362.213911.60470@e3g2000cwe.googlegroups.com...
>> Anil Gupte wrote:
>> <snip>
>>> Anyway, I did not underatand your statement:
>>>
>>> Dim xyz(Columns, Rows) As String
>>>
>>> Do you actually use the words Columns and Rows?  I am doing:
>>> Dim xyz(,) As String
>> <snip>
>>
>> Sorry, I didn't make it clear. What I meant was to treat the first
>> dimmension as the column selector, and the last dimmension as the row
>> selector. So, if you have a table with the columns "Name" and "Age",
>> you'd have:
>>
>>  Dim Items(0 To 1, 0 To -1) As String 'An empty table
>>
>>  '...
>>  'Adds a row:
>>  Dim NewIndex As Integer = Items.GetLength(1)
>>  Redim Preserve Items(0 To 1, 0 To NewIndex)
>>  Items(0, NewIndex) = TheName
>>  Items(1, NewIndex) = TheAge
>>
>> Of course, all this trouble is because you want to extract the data
>> from the original dataset.
>> Another approach could be to use the orginal table:
>>
>>    mData = New DataTable
>>
>>    mData.Columns.Add("ID", GetType(Integer), Nothing)
>>    mData.Columns.Add("Name", GetType(String), Nothing)
>>    mData.Columns.Add("DisplayText", _
>>      GetType(String), "id + ' - ' + name")
>>
>>    mData.Rows.Add(1, "John")
>>    mData.Rows.Add(2, "Mary")
>>    mData.Rows.Add(3, "Lamb")
>>    mData.Rows.Add(4, "Little Pig")
>>
>>    With Me.ComboBox1
>>      .DataSource = mData
>>      .DisplayMember = "DisplayText"
>>      .ValueMember = "ID"
>>
>>      'Selects the item with ID = 4
>>      .SelectedValue = 4
>>    End With
>>
>> HTH
>>
>> Regards,
>>
>> Branco.
>>
>
>