How to ignore a class property using Dapper.net Extensions?

Question

I am using Dapper.net Extensions and would like to ignore certain properties without having to write a complete custom mapper. As you can see in the ClassMapper below there is a lot of redundant code when all I really want to do is ignore one property. What would be the best way to accomplish this?

I like the answer provided here https://stackoverflow.com/a/14649356 but I cannot find the namespace where 'Write' is defined.

public class Photo : CRUD, EntityElement
{
    public Int32 PhotoId { get; set; }
    public Guid ObjectKey { get; set; }
    public Int16 Width { get; set; }
    public Int16 Height { get; set; }
    public EntityObjectStatus ObjectStatus { get; set; }
    public PhotoObjectType PhotoType { get; set; }
    public PhotoFormat2 ImageFormat { get; set; }
    public Int32 CategoryId { get; set; }

    public int SomePropertyIDontCareAbout { get; set; }
}


public class CustomMapper : DapperExtensions.Mapper.ClassMapper<Photo>
{
    public CustomMapper()
    {
        Map(x => x.PhotoId).Column("PhotoId").Key(KeyType.Identity);
        Map(x => x.ObjectKey).Column("ObjectKey");
        Map(x => x.Width).Column("Width");
        Map(x => x.Height).Column("Height");
        Map(x => x.ObjectStatus).Column("ObjectStatus");
        Map(x => x.PhotoType).Column("PhotoType");
        Map(x => x.ImageFormat).Column("ImageFormat");
        Map(x => x.CategoryId).Column("CategoryId");

        Map(f => f.SomePropertyIDontCareAbout).Ignore();
    }
}

Eure

Answer 1

The WriteAttribute class is located in the Dapper.Contrib.Extensions namespace--which is part of the Dapper.Contrib project. You can add that via nuget, the package is named "Dapper.Contrib"

Crouse

The Dapper.Contrib package on Nuget isn't updated with the lates code it seems. I have contacted the owner to get it updated. – Automatic

...and now it is updated and hopefully will be kept updated in the future. – Automatic

Answer 2

As you can see in Person.cs, just call AutoMap(); in constructor of you ClassMapper. For example:

public class CustomMapper : DapperExtensions.Mapper.ClassMapper<Photo>
{
    public CustomMapper()
    {
        Map(x => x.PhotoId).Key(KeyType.Identity);
        Map(f => f.SomePropertyIDontCareAbout).Ignore();
        AutoMap();
    }
}

Vicennial

This could would work. Just that its better to do base.AutoMap() or mark the CustomMapper class as sealed. Thanks – Whiffle

Answer 3

You can decorate the property with [Computed] and the property will be ignored on insert. Semantically it may not be perfect but it seems to do the job:

[Computed]
public int SomePropertyIDontCareAbout { get; set; }

Then again, Peter Ritchie's answer is likely more spot-on with:

[WriteAttribute(false)]
public int SomePropertyIDontCareAbout { get; set; }

Grethel

[WriteAttribute(false)] can be abbreviated as [Write(false)]. – Aalii