Missing operator in query expression 'system.byte[]'

string sqltext = "UPDATE [table] set [column]=? WHERE id=?";

// These must be added in the order they appear in the query string OleDbParameter imageParameter = new OleDbParameter("@image", OleDbType.VarBinary, image.Length);
parameter.Value = command.Parameters.Add(imageParameter);

// This is a bad idea. You're not vetting the value of the TextBox before using it.
command.Parameters.AddWithValue("@id", TextBox1.Text);

string query = "UPDATE PatientVisit SET Barcode=? WHERE DNo=? AND VDate=?";
// NEVER store dates as Text!!
using (OleDbCommand cmd = new OldDbCommand(query, helper.con))
{
    // You cannot use AddWithValue with a binary type.
    cmd.Parameters.Add("Barcode",OleDbType.VarBinary);
    cmd.Parameters["Barcode"].Value = Exportimage;

    // Again, you MUST verify user input before using it!
    // Treat it like the spawn of Satan that it is.
    int dno;
    bool success = int.TryParse(DNo.Text, out dno);
    if (success)
    {
        cmd.Parameters.AddWithValue("@dno", dno);
    }
    
    DateTime vdate;
    success &= DateTime.TryParse(VDate.Text, out vdate);
    if (success)
    {
        cmd.Parameters.AddWithValue("@VDate", vdate);
    }

    if (success)
    {
        cmd.ExecuteNonQuery();
    }
    else
    {
        // Parsing failed somewhere so you're not executing the query.
    }
}