VB.Net MySQL updating

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VB

MySQL

Hi guys
I have done some MySQL connection

MySQLConnection.ConnectionString = "server=127.0.0.1;Port=3307; User ID=root; password=qweqwe; database=test"

      MySQLConnection.Open()
      sql = "SELECT * FROM users where users.user = '" + TextBox1.Text + "';"

      da = New MySqlDataAdapter(sql, MySQLConnection)

      da.Fill(ds, "Mysql")
      MySQLConnection.Close()

but after this when I write

da.Update(ds, "Mysql")

I get an error "Update requires a valid UpdateCommand when passed DataRow collection with modified rows."
Can you help me and say what I am doing wrong thank you :)