VB.net Image Upaditng Problems

Question

Hello I am using Vb.net i want to update Image in PicturePox1 already image save and then when i click Datagirdview want to update but there Error "Empty path name is not legal".

Sub update()
If con.State = ConnectionState.Open Then
con.Close()
End If
con.Open()
qry = "Update Doc Set ID=@ID,IskaGade=@IskaGade,Aqoonsi=@Aqoonsi,Gate=@Gate,MarkhatiKowaaad=@MarkhatiKowaaad,MarkhatiLabaad=@MarkhatiLabaad,MarkhatiSadaxaad=@MarkhatiSadaxaad,Faahfaahin=@Faahfaahin,UserID=@UserID where RefNo=@RefNo"
cmd = New SqlCommand(qry, con)
Dim i As Short
cmd.Parameters.AddWithValue("@ID", txtid.Text)
cmd.Parameters.Add(New SqlClient.SqlParameter("@IskaGade", SqlDbType.Image)).Value = IO.File.ReadAllBytes(a.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("@Aqoonsi", SqlDbType.Image)).Value = IO.File.ReadAllBytes(b.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("@Gate", SqlDbType.Image)).Value = IO.File.ReadAllBytes(c.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("@MarkhatiKowaaad", SqlDbType.Image)).Value = IO.File.ReadAllBytes(d.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("@MarkhatiLabaad", SqlDbType.Image)).Value = IO.File.ReadAllBytes(ex.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("@MarkhatiSadaxaad", SqlDbType.Image)).Value = IO.File.ReadAllBytes(fr.FileName)
cmd.Parameters.AddWithValue("@Faahfaahin", txtremarks.Text)
cmd.Parameters.AddWithValue("@Date", Date.Today.ToShortDateString)
cmd.Parameters.AddWithValue("@UserID", txtUserID.Text)
cmd.Parameters.AddWithValue("@RefNo", txtref.Text)
cmd.ExecuteNonQuery()
MsgBox("Record Updated Successfully")
filldatagrid()

Image Reader in Gridview

Sub readImageMarkhatithree(ByVal ID As String)
Dim dr As SqlDataReader, MyTest As Boolean = False
Dim sql As String
If con.State = ConnectionState.Open Then
con.Close()
End If
con.Open()
sql = "Select MarkhatiSadaxaad from Doc where id ='" & txtid.Text & "'"
cmd = New SqlCommand(sql, con)
cmd.CommandType = CommandType.Text
dr = cmd.ExecuteReader
Do While (dr.Read = True)
Dim bits As Byte()
bits = CType(dr.Item("MarkhatiSadaxaad"), Byte())
Dim memorybits As New MemoryStream(bits)
Dim bitmap As New Bitmap(memorybits)
Markhatisadaxaad.Image = bitmap
Markhatisadaxaad.SizeMode = PictureBoxSizeMode.StretchImage
Loop
dr.Close()
End Sub