Update on Duplicate Value incorrect syntax.

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C#

SQL

Visual-Studio

connection

using (SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True"))
{
    SqlCommand CmdSql = new SqlCommand("INSERT INTO bookList (ISBN,Book,Price,Link) VALUES (@ISBN,@Book,@Price,@Link) ON DUPLICATE KEY UPDATE Price = Price", conn);
    conn.Open();
    CmdSql.Parameters.AddWithValue("@ISBN", isbnCode.Text);
    CmdSql.Parameters.AddWithValue("@Book", bookEntry.Text);
    CmdSql.Parameters.AddWithValue("@Price", priceConvert);
    CmdSql.Parameters.AddWithValue("@Link", getUrl);
    CmdSql.ExecuteNonQuery();
    conn.Close();
}

The following is the table I have:

http://i622.photobucket.com/albums/tt301/kidown/table.jpg

The program gives me "Incorrect syntax near the keyword 'ON'."

Is it because the data value the same?

basically when the data is the same I want to update the Price (if there is a difference in price).

Link is set as primary key since its the only one in the table that has to be unique.

Thanks