--finding compatibility level for the database

SELECT compatibility_level  FROM sys.databases  WHERE name = 'mydbname';

--changing compatibility level for the database

ALTER DATABASE AdventureWorks2022
SET COMPATIBILITY_LEVEL = 150;

//For my database TBS, this is my EF Context+++++++++++++++++++++++++++++++++++++++

public partial class EF_TBS_Context : DbContext
{
    public EF_TBS_Context(DbContextOptions<EF_TBS_Context> options)
        : base(options)
    {
    }

//...a lot of code here......................
}

//this is my Factory pattern +++++++++++++++++++++++++++++++++++++++++++++++++++++
public class EF_TBS_Context_Factory : IDesignTimeDbContextFactory<EF_TBS_Context>
{
    static EF_TBS_Context_Factory()
    {
        //static constructor, can be useful later
    }

    static string? _connectionString = null;
    static byte _compatibilityLevel = 120;

    public static void SetConnectionString(string? connectionString)
    {
        _connectionString=connectionString;
    }

    public static void SetDatabaseCompatibilityLevel(byte compatibilityLevel)
    {
        _compatibilityLevel = compatibilityLevel;
    }

    public EF_TBS_Context CreateDbContext(string[] args)
    {
        var optionsBuilder = new DbContextOptionsBuilder<EF_TBS_Context>();

        optionsBuilder.UseSqlServer(
            _connectionString, o => o.UseCompatibilityLevel(_compatibilityLevel));

        return new EF_TBS_Context(optionsBuilder.Options);
    }
}

//This is how to set Factory static properties++++++++++++++++++++++++++++++++++
EF_TBS_Context_Factory.SetConnectionString("..some connection string...");
EF_TBS_Context_Factory.SetDatabaseCompatibilityLevel(120);

//this is my DatabaseConnectionTest, it also shows usage of Factory pattern+++++
//and it shows how to get in code Database compatibility level
public bool DoConnectionTest(bool ShowDatabaseConnectionStringInLog = false)
{
    bool hasConnection = false;
    Exception? exConnection = null;

    try
    {
        using EF_TBS_Context ctx = _EF_TBS_ContextFactory.CreateDbContext(new string[0]);
        if (ShowDatabaseConnectionStringInLog)
        {
            string? txt1 = ctx.Database.GetConnectionString();
            _logger.LogInformation("Database connection string:[" + txt1 + "]");
        }
        else
        {
            _logger.LogInformation("Logging of Database connection string is disabled");
        }
        string? DatabaseName = null;
        {
            System.Data.Common.DbConnection conn = ctx.Database.GetDbConnection();
            conn.Open();
            DatabaseName = conn.Database;
            string? txt2 = "Database Info: Database[" + conn.Database + "] ";
            txt2 += "DataSource[" + conn.DataSource + "] ";
            txt2 += "ServerVersion[" + conn.ServerVersion + "] ";
            txt2 += "ConnectionTimeout[" + conn.ConnectionTimeout + "] ";
            DbCommand command = conn.CreateCommand();
            txt2 += "DefaultCommandTimeout[" + command.CommandTimeout + "] ";
            conn.Close();
            _logger.LogInformation(txt2);
        }
        {
            if(!String.IsNullOrEmpty(DatabaseName))
            {
                byte compatibility_level = ctx.Database.SqlQuery<byte>(
                $"SELECT compatibility_level AS [Value] FROM sys.databases  WHERE name = {DatabaseName}")
                    .SingleOrDefault();
                string? text5 = $"Database Compatibility level:{compatibility_level.ToString()}";
                _logger.LogInformation(text5);
            }
        }
        hasConnection = true;
    }
    catch (Exception ex)
    {
        hasConnection = false;
        exConnection = ex;
    }

    if (hasConnection)
    {
        string msg = "Database connection test: SUCCESS.";
        _logger.LogInformation(msg);
    }
    else
    {
        string msg = "Database connection test: FAILED." + exConnection?.Message;
        _logger.LogError(msg);
        //_logger.LogError(exConnection, msg);
    }

    return hasConnection;
}