Dapper: C# 9 records

[silkfire]

Are there any plans to add support for records (added in C# 9/.NET 5), more specifically positional records?

[mgravell]

well, we'd need to think about what that means, since positional records still have names; do we bind by constructor parameter name (which would be my expectation)? or by ordinal position? what would you expect to happen here?

[silkfire]

By name sounds most logical to me. See here on how it can be done.

[mgravell]

I'm very familiar; right now, for nominal matching, it needs a parameterless constructor, which means that (if we assume the columns aren't an exact match) this doesn't work:

``` c#
private record PositionalCarRecord(int Age, Car.TrapEnum Trap, string Name)

but this does:

``` c#
private record PositionalCarRecord(int Age, Car.TrapEnum Trap, string Name)
{
    public PositionalCarRecord() : this(default, default, default) { }
}

I'll have to look to see how much work is involved in handling the first case.

[Tornhoof]

I did it by name in spanjson, fwiw it was more work to get mixed records (with extra normal properties) to work than the positional stuff.
Additionally https://stackoverflow.com/questions/63097273/c-sharp-9-0-records-reflection-and-generic-constraints might help, but Marc probably already knows about it.