[Solved] JavaScript Confirmation Box not displaying after upload file using VB.Net in ASP.Net

Sir,

After uploading image to database on Button Click Page goes black and doesn't shows any confirmation message.

Imports System.Data.SqlClient
Imports System.IO

Partial Class SimplaPage
    Inherits System.Web.UI.Page   

    Protected Sub btnFileupload_Click(sender As Object, e As EventArgs) Handles btnFileupload.Click
        'str = vali.tabmgmtdocuments(fileExtension.PostedFile.InputStream, filePrevManagingCommittee.PostedFile.InputStream, fileMinutesMeeting.PostedFile.InputStream, fileEnrollment.PostedFile.InputStream, fileStaffMember.PostedFile.InputStream, fileByLaws.PostedFile.InputStream, filePrev3Yr.PostedFile.InputStream, file10Members.PostedFile.InputStream)

        Dim filename As String = ""
        Dim filePath As String = ""
        'Dim fs As FileStream = New FileStream()
        Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("dsejConnectionString").ConnectionString)
        Dim cmdInsert As New SqlCommand()
        Dim query As String = "update management_approvaltbl set "
        ....
        cmdInsert = New SqlCommand(query, con)
        If Not fileExtension Is Nothing Then
            If fileExtension.HasFile Then
                Dim sizeca = fileExtension.PostedFile.ContentLength
                If checkPhoto(fileExtension.PostedFile.FileName) = False Then
                    lblmsg.Text = "Previous Recognition/Extension/Affiliation order copy " & txt
                    Exit Sub
                End If
                If sizeca > 1000000 Then
                    fileExtension = Nothing
                    lfileExtension.CssClass = "err"
                    lfileExtension.Text = "File size exceeded"
                    Exit Sub
                Else
                    lfileExtension.CssClass = "success"
                    'fileExtension = DirectCast(Session("fileExtension"), FileUpload)
                    filename = Now.Hour & Now.Minute & Now.Second & Now.Millisecond & "_" & fileExtension.PostedFile.FileName.ToString()
                    fileExtension.PostedFile.SaveAs(Server.MapPath("Photo/" & filename))
                    If CheckImage(filename) <> True Then
                        lblmsg.Text = "Kindly Upload Proper File"
                        lfileExtension.Text = "Not a valid .jpg file"
                        Exit Sub
                    End If
                    lfileExtension.Text = filename
                    Dim b1 As Byte() = toBinary(filename)
                    cmdInsert.Parameters.AddWithValue("@prev_recognition_ext_affli_order_copy", Data.SqlDbType.Image).Value = b1
                End If   
            End If  
        End If         
        cmdInsert.Parameters.AddWithValue("@mgmtapprid", 1)
        con.Open()
        Dim i As Integer = cmdInsert.ExecuteNonQuery()
        con.Close()
        If i > 0 Then
            ScriptManager.RegisterStartupScript(Me, Page.GetType, "Script", "displayMessage('Record saved successfully');", True)
            lblmsg.Text = "Record saved successfully."

        Else
            lblmsg.Text = "Some error occured while saving the data."
        End If
    End Sub

    Public Function CheckImage(ByVal file As String) As Boolean
        Dim filePath As String = Server.MapPath("Photo/" & file)
        Dim filename As String = Path.GetFileName(filePath)
        Dim fs As FileStream = New FileStream(filePath, FileMode.Open, FileAccess.Read)
        Dim br As BinaryReader = New BinaryReader(fs)
        Dim bytes As [Byte]() = br.ReadBytes(&H10)
        Dim data_as_hex As String = BitConverter.ToString(bytes)
        Dim magicCheck As String = data_as_hex.Substring(0, 11)
        'Set the contenttype based on File Extension
        Select Case magicCheck
            Case "FF-D8-FF-E1"
                ContentType = "image/jpg"
                Exit Select
            Case "FF-D8-FF-E0"
                ContentType = "image/jpg"
                Exit Select
        End Select
        If ContentType <> [String].Empty Then
            Return True
        Else
            Return False
        End If
    End Function
End Class