entity framework core t-sql at time zone code example

Example: entity framework core t-sql at time zone

//https://stackoverflow.com/questions/63992874/ef-core-group-by-month-and-year-with-utc-dates
public static ReturnType CustomMethod(ArgType arg) => throw new NotImplementedException();

protected override void OnModelCreating(ModelBuilder builder){
    builder.HasDbFunction(typeof(Context).GetMethod(nameof(CustomMethod)));
}

public static DateTimeOffset ToTimeZone(this DateTimeOffset value, string name) => throw new NotImplementedException();

public class SqlFragmentListExpression : SqlExpression
{
    public SqlFragmentListExpression(Type type, RelationalTypeMapping typeMapping, params SqlExpression[] fragments) : base(type, typeMapping)
    {
        Fragments = fragments;
    }

    public SqlExpression[] Fragments { get; }

    public override void Print(ExpressionPrinter expressionPrinter)
    {
        foreach (var f in Fragments)
            f.Print(expressionPrinter);
    }

    protected override Expression VisitChildren(ExpressionVisitor visitor)
    {
        var frags = new SqlExpression[Fragments.Length];
        var changed = false;
        for(var i = 0; i < Fragments.Length; i++)
        {
            frags[i] = (SqlExpression)visitor.Visit(Fragments[i]);
            changed |= frags[i] != Fragments[i];
        }
        return changed ? new SqlFragmentListExpression(Type, TypeMapping, frags) : this;
    }
}

// OnModelCreating
builder                
    .HasDbFunction(typeof(Extensions).GetMethod(nameof(Extensions.ToTimeZone)))
    .HasTranslation(args => {
        var dto = args.ElementAt(0);
        return new SqlFragmentListExpression(dto.Type, dto.TypeMapping,
            dto,
            new SqlFragmentExpression(" AT TIME ZONE "),
            args.ElementAt(1));
    });
    
// use it like
_dbContext.Tickets
    .Where(x => x.Date >= from && x.Date <= to)
    .Select(x => new {
        Date = x.Date.ToTimeZone("Central European Standard Time")
    })
    .GroupBy(x => new {
        Year = x.Date.Year,
        Month = x.Date.Month
    },
    (x, e) => new {
        x.Year,
        x.Month,
        Count = e.Count()
    })