Как добавить расширения к файлу без расширения?

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ComboBox1.SelectedItem = "JPEG"
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Try
            If OpenFileDialog1.ShowDialog() = DialogResult.OK Then
                PictureBox1.Image = System.Drawing.Image.FromFile(OpenFileDialog1.FileName)
            End If
        Catch ex As Exception
        End Try
    End Sub
 
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        If ComboBox1.SelectedItem = "JPEG" Then
            Try
                SaveFileDialog1.Filter = "JPEG |*.jpeg"
                If SaveFileDialog1.ShowDialog() = DialogResult.OK Then
                    PictureBox1.Image.Save(SaveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Jpeg)
                End If
            Catch ex As Exception
            End Try
        End If
        If ComboBox1.SelectedItem = "PNG" Then
            Try
                SaveFileDialog1.Filter = "PNG |*.png"
                If SaveFileDialog1.ShowDialog() = DialogResult.OK Then
                    PictureBox1.Image.Save(SaveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Png)
                End If
            Catch ex As Exception
            End Try
        End If
        If ComboBox1.SelectedItem = "GIF" Then
            Try
                SaveFileDialog1.Filter = "GIF |*.gif"
                If SaveFileDialog1.ShowDialog() = DialogResult.OK Then
                    PictureBox1.Image.Save(SaveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Gif)
                End If
            Catch ex As Exception
            End Try
        End If
        If ComboBox1.SelectedItem = "BMP" Then
            Try
                SaveFileDialog1.Filter = "BMP |*.bmp"
                If SaveFileDialog1.ShowDialog() = DialogResult.OK Then
                    PictureBox1.Image.Save(SaveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Bmp)
                End If
            Catch ex As Exception
            End Try
        End If
        If ComboBox1.SelectedItem = "ICON" Then
            Try
                SaveFileDialog1.Filter = "ICON |*.Icon"
                If SaveFileDialog1.ShowDialog() = DialogResult.OK Then
                    PictureBox1.Image.Save(SaveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Icon)
                End If
            Catch ex As Exception
            End Try
        End If
        If ComboBox1.SelectedItem = "TIFF" Then
            Try
                SaveFileDialog1.Filter = "TIFF |*.tiff"
                If SaveFileDialog1.ShowDialog() = DialogResult.OK Then
                    PictureBox1.Image.Save(SaveFileDialog1.FileName, System.Drawing.Imaging.ImageFormat.Tiff)
                End If
            Catch ex As Exception
            End Try
        End If
    End Sub
End Class