after converting Bitmap back to MemoryStream not saving proper image

I have a data grid view,in update button i wrote code like this:

Dim cid As Integer
        Dim dtid As Integer
        Dim cmpname As String
        Dim dtname As String
        Dim dtPhone As String
        Dim dtEmail As String
        Dim dtimage As Image


        For i As Integer = 0 To gv.RowCount - 2
            ' Dim rv = DirectCast(bSource.Current, DataRowView)
            Dim rv = DirectCast(gv.Rows(i).DataBoundItem, DataRowView)
            cid = rv.Row.Field(Of Integer)("Cid")

            dtid = rv.Row.Field(Of Integer)("dtId")
            cmpname = rv.Row.Field(Of String)("CompanyName")
            dtname = rv.Row.Field(Of String)("Department")
            dtPhone = rv.Row.Field(Of String)("Phone")
            dtEmail = rv.Row.Field(Of String)("Email")

            Using ms As New MemoryStream(rv.Row.Field(Of Byte())("empimage"))
                dtimage = New Bitmap(ms)
            End Using

            adapter.UpdateCommand = New SqlCommand("UPDATE CompanyMaster_tbl SET CompanyName = @CompanyName", con.connect)
            adapter.UpdateCommand = New SqlCommand("update DepartmentMaster_tbl set dtName = @dtName,dtPhone = @dtPhone,dtEmail = @dtEmail,empimage=@dtimage  where dtId=@dtid", con.connect)
            adapter.UpdateCommand.Parameters.AddWithValue("@Cid", cid)
            adapter.UpdateCommand.Parameters.AddWithValue("@CompanyName", cmpname)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtId", dtid)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtName", dtname)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtPhone", dtPhone)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtEmail", dtEmail)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtimage", dtimage)
            adapter.UpdateCommand.ExecuteNonQuery()
        Next

while executing i am getting error in this line :adapter.UpdateCommand.ExecuteNonQuery() Error:No mapping exists from object type System.Drawing.Bitmap to a known managed provider native type so i made small change in my code ..change is
instead of this line 'adapter.UpdateCommand.Parameters.AddWithValue("@dtimage", dtimage)' i added code like this:

Dim md AsNew MemoryStream()
            dtimage.Save(md, System.Drawing.Imaging.ImageFormat.Gif)Dim imagedata AsByte()= md.ToArray()
 adapter.UpdateCommand.Parameters.AddWithValue("@dtimage", imagedata )

after adding this code am not getting any error..but not saving my image..that saving some another thing..what is wrong with my code,,am working on vb.net window application