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POAutomapper Projections and Enum > string converter
 

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    <p>Having a problem using Automapper's <code>Project().To</code> method that does not show up when doing a simple <code>Mapper.Map&lt;&gt;()</code>.</p> <p>I have an enum that is mapped to a string, and a class containing that enum that is mapped to another class containing a string property with the same name as the enum property. </p> <p>When I do a simple <code>Mapper.Map&lt;&gt;()</code> from one class to another, everything works fine. But when I try to do a <code>Project().To()</code>, I get an exception:</p> <pre><code>System.ArgumentException: Type 'System.String' does not have a default construct or at System.Linq.Expressions.Expression.New(Type type) at AutoMapper.MappingEngine.CreateMapExpression(Type typeIn, Type typeOut) at AutoMapper.MappingEngine.CreateMapExpression(Type typeIn, Type typeOut) at AutoMapper.MappingEngine.&lt;CreateMapExpression&gt;b__9[TSource,TDestination](T ypePair tp) at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Fu nc`2 valueFactory) at AutoMapper.MappingEngine.CreateMapExpression[TSource,TDestination]() at AutoMapper.QueryableExtensions.ProjectionExpression`1.To[TResult]() at ConsoleApplication1.Program.Main(String[] args) </code></pre> <p>Here's a code sample that demonstrates the problem:</p> <pre><code>using System; using System.Collections.Generic; using System.ComponentModel.DataAnnotations; using System.Linq; using AutoMapper.QueryableExtensions; namespace ConsoleApplication1 { public static class EnumExtensions { public static string DisplayName(this Enum e) { var field = e.GetType().GetField(e.ToString()); if (field != null) { var display = ((DisplayAttribute[])field.GetCustomAttributes(typeof(DisplayAttribute), false)).FirstOrDefault(); if (display != null) { return display.Name; } } return e.ToString(); } } public enum Foo { [Display(Name = "Thing 1")] Thing1, [Display(Name = "Thing 2")] Thing2 } public class Bar { public Foo SomeFoo { get; set; } public string Name { get; set; } } public class BarViewModel { public string SomeFoo { get; set; } public string Name { get; set; } } class Program { static void Main(string[] args) { try { // map from enum value to enum display name AutoMapper.Mapper.CreateMap&lt;Foo, string&gt;().ConvertUsing(x =&gt; x.DisplayName()); AutoMapper.Mapper.CreateMap&lt;Bar, BarViewModel&gt;(); AutoMapper.Mapper.AssertConfigurationIsValid(); List&lt;Bar&gt; bars = new List&lt;Bar&gt;(); bars.Add(new Bar() { Name = "Name1", SomeFoo = Foo.Thing2 }); bars.Add(new Bar() { Name = "Name2", SomeFoo = Foo.Thing1 }); var barsQuery = (from Bar b in bars select b).AsQueryable(); // works exactly as expected var barViewModesls1 = AutoMapper.Mapper.Map&lt;IEnumerable&lt;BarViewModel&gt;&gt;(barsQuery).ToList(); // throws an exception "Type 'System.String' does not have a default constructor" var barViewModels2 = barsQuery.Project().To&lt;BarViewModel&gt;().ToList(); } catch (Exception ex) { Console.WriteLine(ex.ToString()); } Console.WriteLine("press a key to continue"); Console.ReadKey(); } } } </code></pre>
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    1. USMr. T
    1. USMr. T
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      1. VTUpMod
    2. VO
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      1. VTUpMod
    1. COWhat programming language is this ?
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      1. USNINCOMPOOP
    2. COSorry, it's c#, I added a tag to clarify
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      1. USMr. T
    3. COIt doesn't help you, but I've recreated this in AutoMapper 2.2.1 as well as the the 3.0.0 pre-release. `Foo -> Foo` works, `Foo -> string` doesn't and nor does `string -> Foo`. I'd suggest raising it as an issue [on github project page](https://github.com/AutoMapper/AutoMapper/issues?page=1&state=open). I also noticed you asked on their mailing list which is a good idea - they're pretty active there.
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      1. USMightymuke
 

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