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POIs possible simplify generic class?
 

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    <p>Colleagues, In our project we are using AutoMapper to map models.</p> <p>We have a model:</p> <pre><code>public class Location { public string Address { get; set; } } public class Person { public string Name { get; set;} public Collection&lt;Location&gt; Locations { get; set; } } </code></pre> <p>also we have a view model:</p> <pre><code>public class PersonView { public string Name { get; set; } public string Location { get; set;} } </code></pre> <p>To mapping a model to a view model we may define something like the following:</p> <pre><code>Mapper.CreateMap&lt;Person, PersonView&gt;(d=&gt;d.Name, opt=&gt;opt.FromMap(s=&gt;s.Name); Mapper.CreateMap&lt;Person, PersonView&gt;(d=&gt;d.Address, opt=&gt;opt.FromMap(s=&gt;s.Locations.First().Address); </code></pre> <p>BUT: If Locations will not contains elements or is null then we will get an exception.</p> <p>From other side, we may define a function to get a value:</p> <pre><code>Mapper.CreateMap&lt;Person, PersonView&gt;(d=&gt;d.Address, opt=&gt;opt.FromMap(s=&gt; { var item = s.Locations.FirstOrDefault(); if(item == null) { return string.Empty; } return item.Address; }); </code></pre> <p>This expressions hard to read. And I try create a IValueResolver for simplify mapping.</p> <pre><code>public class CollectionItemResolver&lt;TSource, TSourceItem, TResult&gt; where TSource : class where TSourceItem : class { private readonly Func&lt;TSource, IEnumerable&lt;TSourceItem&gt;&gt; _sourceSelector; private readonly Func&lt;TSourceItem, TResult&gt; _selector; private readonly TResult _defaultValue; public CollectionItemResolver(Func&lt;TSource, IEnumerable&lt;TSourceItem&gt;&gt; source, Func&lt;TSourceItem, TResult&gt; selector) : this(source, selector, default(TResult)) { } public CollectionItemResolver(Func&lt;TSource, IEnumerable&lt;TSourceItem&gt;&gt; source, Func&lt;TSourceItem, TResult&gt; selector, TResult defaultValue) { _sourceSelector = source; _selector = selector; _defaultValue = defaultValue; } public TResult Resolve(TSource source) { var items = _sourceSelector(source); if (items == null) { return _defaultValue; } var item = items.FirstOrDefault(); if (item == null) { return _defaultValue; } var value = _selector(item); return value; } } </code></pre> <p>And then use something like this:</p> <pre><code>Mapper.CreateMap&lt;Person, PersonView&gt;(d=&gt;d.Address, opt=&gt;opt.ResolveUsing( new CollectionItemResolver&lt;Person, Location, string&gt;(p=&gt;p.Locations, i=&gt;i.Address))); </code></pre> <p>Is possible simplify generic resolver? For instance do not define the type of nested item?</p> <pre><code>new CollectionItemResolver&lt;Person, string&gt;(p=&gt;p.Locations, i=&gt;i.Address))); </code></pre> <p>Thanks,</p>
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    1. USDmitriy Sosunov
    1. USDmitriy Sosunov
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      1. VTUpMod
    1. CO`Gents`? What about the ladies reading your question?
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      1. USDarin Dimitrov
    2. CO@DarinDimitrov - +1 for saying that with a straight face.
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      1. USSteve
    3. COI'd go back to the expression. That was much easier to read for me.
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      1. USEnigmativity
 

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