[2.0] problem with insert command

[jsc0624]

What is wrong with this code?
There is a message that says,

Update requires a valid InsertCommand when passed DataRow collection with new rows.

string sql = "select * from tblUserAccount";

        SqlDataAdapter da = new SqlDataAdapter(sql, conn);
        DataSet ds = new DataSet();

        da.Fill(ds, "tblUserAccount");
        DataRow dr = ds.Tables[0].NewRow();
        ds.Tables[0].Rows.Add(dr);

        da.InsertCommand = conn.CreateCommand();



        dr.BeginEdit();
            dr["fname"] = txtFname.Text;
            dr["lname"] = txtLname.Text;
            dr["usernames"] = txtUsername.Text;
            dr["passwords"] = txtPassword1.Text;
        dr.EndEdit();

        da.Update(ds, "tblUserAccount");
        ds.AcceptChanges();

        
        da.Dispose();

        conn.Close();
        conn.Dispose();

How can I fixed this thing?

And if I am going to add the highlighted part as shown below the message is:

ExecuteReader: CommandText property has not been initialized

	
	
string sql = "select * from tblUserAccount";

        SqlDataAdapter da = new SqlDataAdapter(sql, conn);
        DataSet ds = new DataSet();

        da.Fill(ds, "tblUserAccount");
        DataRow dr = ds.Tables[0].NewRow();
        ds.Tables[0].Rows.Add(dr);

        da.InsertCommand = conn.CreateCommand();



        dr.BeginEdit();
            dr["fname"] = txtFname.Text;
            dr["lname"] = txtLname.Text;
            dr["usernames"] = txtUsername.Text;
            dr["passwords"] = txtPassword1.Text;
        dr.EndEdit();

        da.Update(ds, "tblUserAccount");
        ds.AcceptChanges();

        
        da.Dispose();

        conn.Close();
        conn.Dispose();