open file in new window on click from gridview

acctuly i have binded treeview with file system & with treeview i hv binded gridview... m posting my code below...


Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Me.IsPostBack Then
Dim rootFolder As String = Me.Server.MapPath("~\")

' load the treeview based on the folder strucutre
Dim rootNode As New TreeNode("Root", rootFolder)
rootNode.Expanded = True
rootNode.[Select]()
' add the root node
Me.tvFolders.Nodes.Add(rootNode)

' bind sub directories to the treeview
BindDirs(rootFolder, rootNode)

' bind the gridview to the datasource using the root node
BindDirsContents(rootNode, Me.gvFolderItems)
End If
End Sub

'''

'''
'''

''' <param name="sender"></param>
''' <param name="args"></param>
Protected Sub GvFolderItems_RowDataBound(ByVal sender As Object, ByVal args As GridViewRowEventArgs)
If args.Row.RowType = DataControlRowType.DataRow Then
Dim item As System.IO.FileSystemInfo = DirectCast(args.Row.DataItem, System.IO.FileSystemInfo)
Dim imageButton As ImageButton = DirectCast(args.Row.FindControl("btnItemIcon"), ImageButton)

If TypeOf item Is System.IO.DirectoryInfo Then
imageButton.ImageUrl = "Images/folder.gif"
Else
imageButton.ImageUrl = "Images/File.gif"

Dim fileInfo As System.IO.FileInfo = DirectCast(item, System.IO.FileInfo)
Dim lblSize As Label = DirectCast(args.Row.FindControl("lblSize"), Label)
lblSize.Text = String.Format("{0:N0} KB", fileInfo.Length \ 1000)
End If
End If
End Sub

'''

'''
'''

''' <param name="sender"></param>
''' <param name="args"></param>
Protected Sub GvFolderItems_RowCommand(ByVal sender As Object, ByVal args As GridViewCommandEventArgs)
' handle either opening the item or rebinding the grid
If args.CommandName = "ItemClick" Then
Dim name As String = DirectCast(args.CommandArgument, String)
Dim dinfo As New System.IO.DirectoryInfo(Me.tvFolders.SelectedNode.Value)

If System.IO.File.Exists(System.IO.Path.Combine(dinfo.FullName, name)) Then
Dim fileInfo As New System.IO.FileInfo(System.IO.Path.Combine(dinfo.FullName, name))
' they clicked on a file, download it
' to there PC
Me.Response.Clear()
Me.Response.AddHeader("Content-Disposition", "attachment; filename=" & fileInfo.Name)
Me.Response.AddHeader("Content-Length", fileInfo.Length.ToString())
Me.Response.ContentType = "application/octet-stream"
Me.Response.WriteFile(fileInfo.FullName)
Me.Response.[End]()
Else
For Each node As TreeNode In Me.tvFolders.SelectedNode.ChildNodes
If node.Text = name Then
node.Selected = True
node.Expanded = False

' expand the parents
Dim parentNode As TreeNode = node.Parent
While parentNode IsNot Nothing
parentNode.Expanded = False
parentNode = parentNode.Parent
End While

' bind the gridview to the datasource
BindDirsContents(node, Me.gvFolderItems)
Exit For
End If
Next
End If
End If
End Sub

'''

'''
'''

''' <param name="sender"></param>
''' <param name="args"></param>
Protected Sub TvFolders_SelectedNodeChanged(ByVal

Protected Sub TvFolders_SelectedNodeChanged(ByVal sender As Object, ByVal args As EventArgs) Handles tvFolders.SelectedNodeChanged
BindDirsContents(Me.tvFolders.SelectedNode, Me.gvFolderItems)

End Sub

'''

'''
'''

''' <param name="node"></param>
Private Shared Sub BindDirsContents(ByVal node As TreeNode, ByVal gridView As System.Web.UI.WebControls.GridView)
' bind the gridview to the datasource
Try
gridView.DataSource = New System.IO.DirectoryInfo(node.Value).GetFileSystemInfos()

gridView.DataBind()
Catch ex As Exception

End Try
End Sub

'''

'''
'''

''' <param name="path"></param>
''' <param name="treeNode"></param>
Private Shared Sub BindDirs(ByVal path As String, ByVal treeNode As TreeNode)
If Not String.IsNullOrEmpty(path) Then
For Each directoryPath As String In System.IO.Directory.GetDirectories(path)
Dim directory As New System.IO.DirectoryInfo(directoryPath)
Dim subNode As New TreeNode(directory.Name, directory.FullName)
treeNode.ChildNodes.Add(subNode)
' bind sub directories
BindDirs(directoryPath, subNode)
''Dim Files As System.IO.FileInfo() = directory.GetFiles()
''For FileCount As Integer = 0 To Files.Length - 1
'' treeNode.ChildNodes.Add(New TreeNode(Files(FileCount).Name))
''Next
' if the parent node is null, return this node
Next
End If
End Sub