.net – AutoMapper: “Ignore the rest”

automappernet

Is there a way to tell AutoMapper to ignore all of the properties except the ones which are mapped explicitly?

I have external DTO classes which are likely to change from the outside and I want to avoid specifying each property to be ignored explicitly, since adding new properties will break the functionality (cause exceptions) when trying to map them into my own objects.

Best Answer

From what I understood the question was that there are fields on the destination which doesn't have a mapped field in the source, which is why you are looking for ways to Ignore those non mapped destination fields.

Instead of implementing and using these extension method you could simply use

Mapper.CreateMap<sourceModel, destinationModel>(MemberList.Source);

Now the automapper knows that it needs to only validate that all the source fields are mapped but not the other way around.

You can also use:

Mapper.CreateMap<sourceModel, destinationModel>(MemberList.Destination);

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – Should ‘using’ directives be inside or outside the namespace

There is actually a (subtle) difference between the two. Imagine you have the following code in File1.cs:

// File1.cs
using System;
namespace Outer.Inner
{
    class Foo
    {
        static void Bar()
        {
            double d = Math.PI;
        }
    }
}

Now imagine that someone adds another file (File2.cs) to the project that looks like this:

// File2.cs
namespace Outer
{
    class Math
    {
    }
}

The compiler searches Outer before looking at those using directives outside the namespace, so it finds Outer.Math instead of System.Math. Unfortunately (or perhaps fortunately?), Outer.Math has no PI member, so File1 is now broken.

This changes if you put the using inside your namespace declaration, as follows:

// File1b.cs
namespace Outer.Inner
{
    using System;
    class Foo
    {
        static void Bar()
        {
            double d = Math.PI;
        }
    }
}

Now the compiler searches System before searching Outer, finds System.Math, and all is well.

Some would argue that Math might be a bad name for a user-defined class, since there's already one in System; the point here is just that there is a difference, and it affects the maintainability of your code.

It's also interesting to note what happens if Foo is in namespace Outer, rather than Outer.Inner. In that case, adding Outer.Math in File2 breaks File1 regardless of where the using goes. This implies that the compiler searches the innermost enclosing namespace before it looks at any using directive.

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – Should ‘using’ directives be inside or outside the namespace

Related Topic