# 10.0 Upgrade Guide

[Release notes](https://github.com/AutoMapper/AutoMapper/releases/tag/v10.0.0).

## All collections are mapped by default, even if they have no setter

You'll have to explicitly ignore those you don't want mapped. See also [this](https://github.com/AutoMapper/AutoMapper/issues/3449#issuecomment-651522397).

## Matching constructor parameters will be mapped from the source, even if they are optional

You can always rename things or use an explicit `MapFrom`.

## `Context.Mapper.Map` overloads that receive a context were removed

Not needed, because the context is passed by default, so you can change the context instance you already have.

## `UseDestinationValue` is now inherited by default

You can override that with `DoNotUseDestinationValue`.

## `AllowNull` allows you to override per member `AllowNullDestinationValues` and `AllowNullCollections`

This used to be ignored for `Map`. Now it's consistent with `ProjectTo`.

## The `ResolutionContext` no longer has a public constructor

You can test the entire `Map` operation.

## Mapping from `dynamic` in .NET 4.6.1

Due to a refactoring of `IMapper`, you might need to add a cast to `object` when mapping from `dynamic`.

## Source validation

Only simple source members expressions are considered, `MapFrom(d => d.Member, s => s.SourceMember)`.

## `MaxDepth`

When reaching `MaxDepth`, destination collections are null/empty, they used to contain `null` values.

## String based `MapFrom`-s are reversed now, also applies to attribute mapping

You can always not use it and explicitly create the reverse map. Or ignore the reversed member.

## `ReverseMap` will also reverse the naming conventions

You can always not use it and explicitly create the reverse map.