Object does not match target type.

[rn5a]

Consider the following code:

<script runat="server">
Sub Page_Load(ByVal obj As Object, ByVal ea As EventArgs)
Dim dInfo As DirectoryInfo

dInfo = New DirectoryInfo(Server.MapPath("/Folder1"))
dgFD.DataSource = dInfo.GetFiles("*.*")
dgFD.DataBind()
End Sub
</script>
<form runat="server">
<aspataGrid ID="dgFD" runat="server"/>
</form>

The above code works fine & populates the DataGrid with all the files
residing in the directory named "Folder1". But it doesn't get the sub-
directories residing in "Folder1". In order to populate the DataGrid
with both the files & sub-directories residing in "Folder1", I
replaced the line

dgFD.DataSource = dInfo.GetFiles("*.*")

with

dgFD.DataSource = dInfo.GetFileSystemInfos("*.*")

But now when I run the above code, ASP.NET generates the following
error:

Object does not match target type.

pointing to the line

dgFD.DataBind()

What is wrong with the above code? How do I populate the DataGrid with
both the files as well as the sub-directories residing in the
directory named "Folder1"?

 

[Mark Fitzpatrick]

First, have you checked to make sure that you aren't getting a null value or
empty array when you call the GetFileSystemInfos method? I can't think of
anything else that may cause it since the FileSystemInfo class is the base
of the FileInfo.

 

[Guest]

Hi there guys,

He gets exception because data source contains two types of objects. Even if
they inherit from the same base class, data binder checks the actual type (it
does not matter if you use base class in source array because polymorphic
call to GetType() will return real type of every element) which can be
FileInfo or DirectoryInfo. This only happens when you use AutoGenerateColumns
because, grid control enumerates all properties for every DataItem (meaning
for every single row). To resolve the problem, declare columns directly (note
there are some incompatibilities such Name):

-- begin aspx code --
<aspataGrid runat="server" ID="dgFD" AutoGenerateColumns="false">
<Columns>
<asp:BoundColumn DataField="FullName" HeaderText="Name"/>
<asp:BoundColumn DataField="CreationTime" HeaderText="Created" />
</Columns>
</aspataGrid>
-- end aspx code –

-- begin vb.net code –
Dim directory As New System.IO.DirectoryInfo(Server.MapPath("~/"))

If directory.Exists Then

Dim files() As System.IO.FileSystemInfo = directory.GetFiles()
Dim directories() As System.IO.FileSystemInfo = directory.GetDirectories()
Dim both(files.Length + directories.Length) As System.IO.FileSystemInfo

Array.Copy(files, 0, both, 0, files.Length)
Array.Copy(directories, 0, both, files.Length - 1, directories.Length)

dgFD.DataSource = both
dgFD.DataBind()

End If
-- end vb code --

Hope this helps

 

[rn5a]

Hi there guys,

He gets exception because data source contains two types of objects. Even if
they inherit from the same base class, data binder checks the actual type (it
does not matter if you use base class in source array because polymorphic
call to GetType() will return real type of every element) which can be
FileInfo or DirectoryInfo. This only happens when you use AutoGenerateColumns
because, grid control enumerates all properties for every DataItem (meaning
for every single row). To resolve the problem, declare columns directly (note
there are some incompatibilities such Name):

-- begin aspx code --
<aspataGrid runat="server" ID="dgFD" AutoGenerateColumns="false">
<Columns>
<asp:BoundColumn DataField="FullName" HeaderText="Name"/>
<asp:BoundColumn DataField="CreationTime" HeaderText="Created" />
</Columns>
</aspataGrid>
-- end aspx code -

-- begin vb.net code -
Dim directory As New System.IO.DirectoryInfo(Server.MapPath("~/"))

If directory.Exists Then

Dim files() As System.IO.FileSystemInfo = directory.GetFiles()
Dim directories() As System.IO.FileSystemInfo = directory.GetDirectories()
Dim both(files.Length + directories.Length) As System.IO.FileSystemInfo

Array.Copy(files, 0, both, 0, files.Length)
Array.Copy(directories, 0, both, files.Length - 1, directories.Length)

dgFD.DataSource = both
dgFD.DataBind()

End If
-- end vb code --

Hope this helps






- Show quoted text -

Thanks a lot, Milosz. Your code certainly did help a lot but as you
have pointed out, there are some incompatibilities like Name. Length
(used to find the size of a file) is another such incompatibility. How
do you overcome these incompatibilities?

Thanks once again....

 

[Guest]

Hi there again,

No problem at all, unfortunatelly we have to do it manually (i little bit
more coding). BTW i completely forgot vb.net differes from c# in array
declaration and there was a bug in my last snippet. Please forgive me but i'm
strictly c# man Anyway, it should go as following:

-- begin aspx page code --

<aspataGrid runat="server" ID="dgFD" AutoGenerateColumns="false">
<Columns>
<asp:TemplateColumn>
<HeaderTemplate>
Name
</HeaderTemplate>
<ItemTemplate>
<asp:Literal runat="server" ID="name" />
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn>
<HeaderTemplate>
Created
</HeaderTemplate>
<ItemTemplate>
<asp:Literal runat="server" ID="created" />
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn>
<HeaderTemplate>
Size
</HeaderTemplate>
<ItemTemplate>
<asp:Literal runat="server" ID="Size" />
</ItemTemplate>
</asp:TemplateColumn>
</Columns>
</aspataGrid>

-- end aspx page code --

-- begin vb.net code behind --

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
_
Handles Me.Load

If Not IsPostBack Then

Dim directory As New System.IO.DirectoryInfo(Server.MapPath("~/"))

If directory.Exists Then

Dim files() As System.IO.FileSystemInfo = directory.GetFiles()
Dim directories() As System.IO.FileSystemInfo = directory.GetDirectories()
Dim both(files.Length + directories.Length - 1) As System.IO.FileSystemInfo

Array.Copy(files, 0, both, 0, files.Length)
Array.Copy(directories, 0, both, files.Length, directories.Length)

dgFD.DataSource = both
dgFD.DataBind()

End If

End If

End Sub


Protected Sub dgFD_ItemDataBound(ByVal sender As Object, _
ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) _
Handles dgFD.ItemDataBound

Dim item As DataGridItem = e.Item

If item.ItemType = ListItemType.Item Or _
item.ItemType = ListItemType.AlternatingItem Then

Dim fileInfo As System.IO.FileSystemInfo = _
CType(item.DataItem, System.IO.FileSystemInfo)

Dim literal As Literal

' name
literal = CType(item.FindControl("name"), Literal)
literal.Text = fileInfo.Name

' creation time
literal = CType(item.FindControl("created"), Literal)
literal.Text = fileInfo.CreationTime.ToString()

If TypeOf fileInfo Is System.IO.FileInfo Then
'size
literal = CType(item.FindControl("length"), Literal)
literal.Text = CType(fileInfo, _
System.IO.FileInfo).Length.ToString()
End If


End If

End Sub


-- end vb.net code behind --

Hope it helps

Milosz