Separating code out into a .dll, thoughts?

[OCD Dan]

I'm trying to wrap my head around creating dll, and since I've been using a variation of the code below, i was wondering if someone could comment on if it would be possible to separate the code from the form and create a dll with it, I've been using this in my application successfully and since I'm familiar with it, I thought it would be a good project to learn on, thanks to who ever actually wrote the code to begin with.

this is the code for the form docViewerForm.vb

Imports System.Data.SqlClient
Imports System.Threading
Imports System.IO

Public Class docViewerForm
    Private Declare Function ShellEx Lib "shell32.dll" Alias "ShellExecuteA" ( _
    ByVal hWnd As Integer, ByVal lpOperation As String, _
    ByVal lpFile As String, ByVal lpParameters As String, _
    ByVal lpDirectory As String, ByVal nShowCmd As Integer) As Integer


    Dim SConnectionString As String = _
        "Initial Catalog=TEST;Data Source=localhost;" & _
        "Integrated Security=SSPI;Persist Security Info=False"
    Dim connection As SqlConnection
    Public Sub New()

        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        Application.EnableVisualStyles()

        ' Add any initialization after the InitializeComponent() call

        Me.lblUploadStatus.Text = ""

        connection = New SqlConnection(SConnectionString)
        Me.WindowState = FormWindowState.Maximized
    End Sub

    Private Sub cmdUpload_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdUpload.Click
        Me.lblUploadStatus.Text = ""
        If LTrim(RTrim(txtFileToUpload.Text)) = "" Then
            lblUploadStatus.Text = "Enter File Name"
            txtFileToUpload.Focus()
            Exit Sub
        End If

        'Call Upload Images Or File
        Dim sFileToUpload As String = ""

        sFileToUpload = LTrim(RTrim(txtFileToUpload.Text))
        Dim Extension As String = System.IO.Path.GetExtension(sFileToUpload)
        'If StrComp(Extension, ".bmp", CompareMethod.Text) = 0 Or Extension = ".jpg" Or Extension = ".img" Or Extension = ".png" Or Extension = ".gif" Then
        If StrComp(Extension, ".bmp", CompareMethod.Text) = 0 Or _
        StrComp(Extension, ".jpg", CompareMethod.Text) = 0 Or _
        StrComp(Extension, ".jpeg", CompareMethod.Text) = 0 Or _
        StrComp(Extension, ".png", CompareMethod.Text) = 0 Or _
        StrComp(Extension, ".gif", CompareMethod.Text) = 0 Then
            upLoadImageOrFile(sFileToUpload, "Image")
        Else 'Pass the extension
            upLoadImageOrFile(sFileToUpload, Extension)
        End If

    End Sub
    Private Sub cmdBrowse_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdBrowse.Click

        Using OpenFileDialog As OpenFileDialog = Me.GetOpenFileDialog()

            If (OpenFileDialog.ShowDialog(Me) = DialogResult.OK) Then
                txtFileToUpload.Text = OpenFileDialog.FileName

            Else 'Cancel
                Exit Sub
            End If
        End Using
        
    End Sub
    'Get table rows from sql server to be displayed in Datagrid. 
    Private Sub GetImagesFromDatabase()
        Try

            'Initialize SQL Server Connection 
            If connection.State = ConnectionState.Closed Then
                connection.Open()
            End If

            Dim strSql As String = "Select FileId,FileName," & _
            "FileType,[Added On] from FileStore"

            'Initialize SQL adapter. 
            Dim ADAP As New SqlDataAdapter(strSql, connection)

            'Initialize Dataset. 
            Dim DS As New DataSet()

            'Fill dataset with FileStore table. 
            ADAP.Fill(DS, "FileStore")

            'Fill Grid with dataset. 
            dbGridView.DataSource = DS.Tables("FileStore")

            'Add Button Starts

            Dim dgButtonColumn As New DataGridViewButtonColumn
            dgButtonColumn.HeaderText = ""
            dgButtonColumn.UseColumnTextForButtonValue = True
            dgButtonColumn.Text = "View File"
            dgButtonColumn.Name = "ViewFile"
            dgButtonColumn.ToolTipText = "View File"
            dgButtonColumn.AutoSizeMode = DataGridViewAutoSizeColumnMode.DisplayedCellsExceptHeader
            dgButtonColumn.FlatStyle = FlatStyle.System
            dgButtonColumn.DefaultCellStyle.BackColor = Color.Gray
            dgButtonColumn.DefaultCellStyle.ForeColor = Color.White
            dbGridView.Columns.Add(dgButtonColumn)


        Catch ex As Exception
            MessageBox.Show(ex.ToString())
            MessageBox.Show("Could not load the Image")
        End Try
    End Sub

    Private Sub dbGridView_CellContentClick(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles dbGridView.CellContentClick
        Dim strSql As String = ""
        Me.lblUploadStatus.Text = ""
        Try
            Select Case e.ColumnIndex
                Case Is > -1
                    If sender.Columns(e.ColumnIndex).Name = "ViewFile" Then
                        Select Case dbGridView.Rows(e.RowIndex).Cells("FileType").Value

                            Case "Image"
                                'For Image
                                strSql = "Select ImageData from FileStore WHERE FileId=" & dbGridView.Rows(e.RowIndex).Cells("FileId").Value

                                Dim sqlCmd As New SqlCommand(strSql, connection)

                                'Get image data from DB
                                Dim imageData As Byte() = DirectCast(sqlCmd.ExecuteScalar(), Byte())

                                'Initialize image variable 
                                Dim newImage As Image = Nothing

                                If Not imageData Is Nothing Then
                                    'Read image data into a memory stream 
                                    Using ms As New MemoryStream(imageData, 0, imageData.Length)
                                        ms.Write(imageData, 0, imageData.Length)
                                        'Set image variable value using memory stream. 
                                        newImage = Image.FromStream(ms, True)
                                    End Using

                                    'set picture 
                                    Dim myPicForm As New docViewerSubForm(newImage)
                                    'newImage.Save("E:\TESTSave.jpg", System.Drawing.Imaging.ImageFormat.Jpeg)
                                    myPicForm.ShowDialog()
                                    'pictureBox1.Image = newImage
                                End If

                            Case ".txt", ".pdf", ".doc"
                                downLoadFile(dbGridView.Rows(e.RowIndex).Cells("FileId").Value, dbGridView.Rows(e.RowIndex).Cells("FileName").Value, dbGridView.Rows(e.RowIndex).Cells("FileType").Value)

                        End Select

                    End If

            End Select
        Catch ex As Exception
            MessageBox.Show(ex.ToString())
        End Try

    End Sub
    Private Sub downLoadFile(ByVal iFileId As Long, ByVal sFileName As String, ByVal sFileExtension As String)
        Dim strSql As String
        'For Document
        Try
            'Get image data from gridview column. 
            strSql = "Select ImageData from FileStore WHERE FileId=" & iFileId

            Dim sqlCmd As New SqlCommand(strSql, connection)

            'Get image data from DB
            Dim fileData As Byte() = DirectCast(sqlCmd.ExecuteScalar(), Byte())

            Dim sTempFileName As String = Application.StartupPath & "\" & sFileName

            If Not fileData Is Nothing Then
                'Read image data into a file stream 
                Using fs As New FileStream(sFileName, FileMode.OpenOrCreate, FileAccess.Write)
                    fs.Write(fileData, 0, fileData.Length)
                    'Set image variable value using memory stream. 
                    fs.Flush()
                    fs.Close()
                End Using

                'Open File
                ' 10 = SW_SHOWDEFAULT
                ShellEx(Me.Handle, "Open", sFileName, "", "", 10)
            End If

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub
    Private Sub upLoadImageOrFile(ByVal sFilePath As String, ByVal sFileType As String)
        Dim SqlCom As SqlCommand
        Dim imageData As Byte()
        Dim sFileName As String
        Dim qry As String

        Try
            'Read Image Bytes into a byte array 

            'Initialize SQL Server Connection 
            If connection.State = ConnectionState.Closed Then
                connection.Open()
            End If

            imageData = ReadFile(sFilePath)
            sFileName = System.IO.Path.GetFileName(sFilePath)

            'Set insert query 
            qry = "insert into FileStore (FileName,ImageData," & _
            "FileType,[Added On]) values(@FileName, @ImageData," & _
            "@FileType,@AddedOn)"

            'Initialize SqlCommand object for insert. 
            SqlCom = New SqlCommand(qry, connection)

            'We are passing File Name and Image byte data as sql parameters. 

            SqlCom.Parameters.Add(New SqlParameter("@FileName", sFileName))
            SqlCom.Parameters.Add(New SqlParameter("@ImageData", DirectCast(imageData, Object)))

            SqlCom.Parameters.Add(New SqlParameter("@FileType", sFileType))
            SqlCom.Parameters.Add(New SqlParameter("@AddedOn", Now()))

            SqlCom.ExecuteNonQuery()
            lblUploadStatus.Text = "File uploaded successfully"

            Me.txtFileToUpload.Text = ""

        Catch ex As Exception
            MessageBox.Show(ex.ToString())
            lblUploadStatus.Text = "File could not uploaded"
        End Try

    End Sub
    'Open file in to a filestream and read data in a byte array. 
    Private Function ReadFile(ByVal sPath As String) As Byte()
        'Initialize byte array with a null value initially. 
        Dim data As Byte() = Nothing

        'Use FileInfo object to get file size. 
        Dim fInfo As New FileInfo(sPath)
        Dim numBytes As Long = fInfo.Length

        'Open FileStream to read file 
        Dim fStream As New FileStream(sPath, FileMode.Open, FileAccess.Read)

        'Use BinaryReader to read file stream into byte array. 
        Dim br As New BinaryReader(fStream)

        'When you use BinaryReader, you need to supply number of bytes to read from file. 
        'In this case we want to read entire file. So supplying total number of bytes. 
        data = br.ReadBytes(CInt(numBytes))

        Return data
    End Function
    Private Function GetOpenFileDialog() As OpenFileDialog
        Dim openFileDialog As New OpenFileDialog

        openFileDialog.CheckPathExists = True
        openFileDialog.CheckFileExists = True

        openFileDialog.Filter = "Image Files (*.bmp;*.jpg;*.jpeg;*.GIF)|*.bmp;*.jpg;*.jpeg;*.GIF|" + _
            "PNG files (*.png)|*.png|text files (*.text)|*.txt|doc files (*.doc)|*.doc|pdf files (*.pdf)|*.pdf"


        openFileDialog.Multiselect = False
        openFileDialog.AddExtension = True
        openFileDialog.ValidateNames = True
        openFileDialog.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Desktop)

        Return openFileDialog
    End Function
    Private Sub cmdView_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdView.Click

        dbGridView.DataSource = Nothing
        dbGridView.Columns.Clear()

        GetImagesFromDatabase()
    End Sub

    Private Sub docViewerForm_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        Try
            If connection.State = ConnectionState.Open Then
                connection.Close()
                connection.Dispose()
            End If
        Catch ex As Exception

        End Try
    End Sub
End Class

[Shaggy Hiker]

Go for it. It looks like nothing more than a form, and there isn't any problem with putting that into a dll. You would just create a new project of type Class Library. By default, such a project will not have a reference to Windows.Forms, so if you were to add that form to the project, you would get a bunch of errors, which can all be resolved by adding the proper reference. Other than that, there doesn't appear to be anything problematic.