You refer the following sample code to use ADO.NET in Asp.net 6 program.cs:
//required using Microsoft.Data.SqlClient;
app.MapGet("/movies", () =>
{
var movies = new List<Movie>();
//to get the connection string
var _config = app.Services.GetRequiredService<IConfiguration>();
var connectionstring = _config.GetConnectionString("DefaultConnection");
//build the sqlconnection and execute the sql command
using (SqlConnection conn = new SqlConnection(connectionstring))
{
conn.Open();
string commandtext = "select MovieId, Title, Genre from Movie";
SqlCommand cmd = new SqlCommand(commandtext, conn);
var reader = cmd.ExecuteReader();
while (reader.Read())
{
var movie = new Movie()
{
MovieId = Convert.ToInt32(reader["MovieId"]),
Title = reader["Title"].ToString(),
Genre = reader["Genre"].ToString()
};
movies.Add(movie);
}
}
return movies;
});
The result like this:

SqlConnection,SqlCommandetc. classes from ADO.NET in .NET 6 - no problem. There are tons of resources showing you how to do this exactly. Make use of theMicrosoft.Data.SqlClientnuget package - see this article as a starting point