storing image in Access table

8 Feb 2006 5:16 AM

anewbie @ VB.NET via DotNetMonster.com

hi.

ive been searching for help with storing images in access. after much
hunting i found this bit of code that Cor Ligthert put up on another forum.
but when i try to update to the dataset, i get this error: system.argument.
exception in system.data.dll, cannot change data type of a column once it has
data.

for one thing my column is empty, for another, i get that message even when i
select "upload to dataset" without first selecting an image.

can someone please help?

\\\it needs a picturebox and four buttons on a page.
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> Private abyt() As Byte
> Private fo As New OpenFileDialog
> Private sf As New SaveFileDialog

> Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles Button1.Click
> 'Reading a picture and put it in a bytearray
> If fo.ShowDialog = DialogResult.OK Then
> Dim fs As New IO.FileStream(fo.FileName, _
> IO.FileMode.Open)
> Dim br As New IO.BinaryReader(fs)
> abyt = br.ReadBytes(CInt(fs.Length))
> br.Close()
> 'just to show the sample without a fileread error
> Dim ms As New IO.MemoryStream(abyt)
> Me.PictureBox1.Image = Image.FromStream(ms)
> End If
> End Sub

> Private Sub Button2_Click(ByVal sender As System.Object, ByVal _
> e As System.EventArgs) Handles Button2.Click
> 'writing a picture from a bytearray
> If sf.ShowDialog = DialogResult.OK Then
> Dim fs As New IO.FileStream(sf.FileName, _
> IO.FileMode.CreateNew)
> Dim bw As New IO.BinaryWriter(fs)
> bw.Write(abyt)
> bw.Close()
> End If
> End Sub

> Private Sub Button3_Click(ByVal sender As System.Object, ByVal _
> e As System.EventArgs) Handles Button3.Click
> 'writing a bytearray to a dataset
> Dim ds As New DataSet
> ds.Tables.Add(New DataTable("Photo"))
> ds.Tables(0).Columns.Add(New DataColumn("Sample"))
> ds.Tables(0).Columns(0).DataType =
> System.Type.GetType("System.Byte[]")
> ds.Tables(0).Rows.Add(ds.Tables(0).NewRow)
> ds.Tables(0).Rows(0)(0) = abyt
> Dim sf As New SaveFileDialog
> If sf.ShowDialog = DialogResult.OK Then
> ds.WriteXml(sf.FileName, XmlWriteMode.WriteSchema)
> End If
> End Sub

> Private Sub Button4_Click(ByVal sender As System.Object, _
> ByVal e As System.EventArgs) Handles Button4.Click
> 'reading a picture from a dataset
> Dim ds As New DataSet
> If fo.ShowDialog = DialogResult.OK Then
> ds.ReadXml(fo.FileName)
> End If
> abyt = CType(ds.Tables(0).Rows(0)(0), Byte())
> Dim ms As New IO.MemoryStream(abyt)
> Me.PictureBox1.Image = Image.FromStream(ms)
> End Sub
> ///
>
> Cor

thanks.

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8 Feb 2006 7:40 AM

Cor Ligthert [MVP]

Anewbie,

I tested the sample again and could not find really errors. (withouth a part
that could go wrong in wrong sequence (try to read a dataset and than
abording), I changed that).

http://www.vb-tips.com/default.aspx?ID=0bf3f72d-b722-459d-8a46-38b5a2f7fdf0

However I have the idea that your problem has not to do with this, but just
with reading and writing a dataset to/from an access database. Can you
explain it a little bit more.

Cor

However in my idea

"anewbie @ VB.NET via DotNetMonster.com" <u16975@uwe> schreef in bericht

news:5b8e90a30b2ec@uwe...
Show quoteHide quote

> hi.
>
> ive been searching for help with storing images in access. after much
> hunting i found this bit of code that Cor Ligthert put up on another
> forum.
> but when i try to update to the dataset, i get this error:
> system.argument.
> exception in system.data.dll, cannot change data type of a column once it
> has
> data.
>
> for one thing my column is empty, for another, i get that message even
> when i
> select "upload to dataset" without first selecting an image.
>
> can someone please help?
>
> \\\it needs a picturebox and four buttons on a page.
>> Private abyt() As Byte
>> Private fo As New OpenFileDialog
>> Private sf As New SaveFileDialog
>
>
>> Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles Button1.Click
>> 'Reading a picture and put it in a bytearray
>> If fo.ShowDialog = DialogResult.OK Then
>> Dim fs As New IO.FileStream(fo.FileName, _
>> IO.FileMode.Open)
>> Dim br As New IO.BinaryReader(fs)
>> abyt = br.ReadBytes(CInt(fs.Length))
>> br.Close()
>> 'just to show the sample without a fileread error
>> Dim ms As New IO.MemoryStream(abyt)
>> Me.PictureBox1.Image = Image.FromStream(ms)
>> End If
>> End Sub
>
>
>> Private Sub Button2_Click(ByVal sender As System.Object, ByVal _
>> e As System.EventArgs) Handles Button2.Click
>> 'writing a picture from a bytearray
>> If sf.ShowDialog = DialogResult.OK Then
>> Dim fs As New IO.FileStream(sf.FileName, _
>> IO.FileMode.CreateNew)
>> Dim bw As New IO.BinaryWriter(fs)
>> bw.Write(abyt)
>> bw.Close()
>> End If
>> End Sub
>
>
>> Private Sub Button3_Click(ByVal sender As System.Object, ByVal _
>> e As System.EventArgs) Handles Button3.Click
>> 'writing a bytearray to a dataset
>> Dim ds As New DataSet
>> ds.Tables.Add(New DataTable("Photo"))
>> ds.Tables(0).Columns.Add(New DataColumn("Sample"))
>> ds.Tables(0).Columns(0).DataType =
>> System.Type.GetType("System.Byte[]")
>> ds.Tables(0).Rows.Add(ds.Tables(0).NewRow)
>> ds.Tables(0).Rows(0)(0) = abyt
>> Dim sf As New SaveFileDialog
>> If sf.ShowDialog = DialogResult.OK Then
>> ds.WriteXml(sf.FileName, XmlWriteMode.WriteSchema)
>> End If
>> End Sub
>
>
>> Private Sub Button4_Click(ByVal sender As System.Object, _
>> ByVal e As System.EventArgs) Handles Button4.Click
>> 'reading a picture from a dataset
>> Dim ds As New DataSet
>> If fo.ShowDialog = DialogResult.OK Then
>> ds.ReadXml(fo.FileName)
>> End If
>> abyt = CType(ds.Tables(0).Rows(0)(0), Byte())
>> Dim ms As New IO.MemoryStream(abyt)
>> Me.PictureBox1.Image = Image.FromStream(ms)
>> End Sub
>> ///
>>
>> Cor
>
> thanks.
>
> --
> Message posted via http://www.dotnetmonster.com

8 Feb 2006 9:47 AM

anewbie @ VB.NET via DotNetMonster.com

hi! thanks for the help... i dont understand - why am i alone getting that
error! hmm. strange. anyhow, my problem is this: im creating a database for
managing personnel records, and id like to have the employees passport sized
photograph displayed in the main form.

im able to store the file path properly, but i dont understand this image
memory streaming bit. i was told theres an image load option in vb... would i
be able to use that to upload, save and display my images?

thanks

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http://www.dotnetmonster.com/Uwe/Forums.aspx/dotnet-vb-net/200602/1

8 Feb 2006 10:21 AM

Cor Ligthert [MVP]

Anewbie,

I thought that the most problems were with Access in this the type of the
datafield.

I thought it was something as binary.

Cor