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POEF 4.1 Code First - map enum wrapper as complex type
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  1. POEF 4.1 Code First - map enum wrapper as complex type
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    copied!<p>I'm trying to build a generic solution to the problem of enums with EF 4.1. My solution is basically a generic version of <a href="http://blogs.msdn.com/b/alexj/archive/2009/06/05/tip-23-how-to-fake-enums-in-ef-4.aspx">How to fake enums in ef 4</a>. The enum wrapper class works wonderfully in the rest of the code and allows code like:</p> <pre><code>EnumWrapper&lt;Color&gt; c = Color.Red; </code></pre> <p>Here's the enum wrapper class:</p> <pre><code>public class EnumWrapper&lt;TEnum&gt; where TEnum : struct, IConvertible { public EnumWrapper() { if (!typeof(TEnum).IsEnum) throw new ArgumentException("Not an enum"); } public TEnum Enum { get; set; } public int Value { get { return Convert.ToInt32(Enum); } set { Enum = (TEnum)(object)value; } } public static implicit operator TEnum(EnumWrapper&lt;TEnum&gt; w) { if (w == null) return default(TEnum); else return w.Enum; } public static implicit operator EnumWrapper&lt;TEnum&gt;(TEnum e) { return new EnumWrapper&lt;TEnum&gt;() { Enum = e }; } public static implicit operator int(EnumWrapper&lt;TEnum&gt; w) { if (w == null) return Convert.ToInt32(default(TEnum)); else return w.Value; } } </code></pre> <p>enum:</p> <pre><code>public enum Color { red = 1, green = 2, blue = 3 } </code></pre> <p>POCO:</p> <pre><code>public class ChickenSandwich { public ChickenSandwich() { CheeseColor = new EnumWrapper&lt;Color&gt;(); } public int ID { get; set; } public string Name { get; set; } public EnumWrapper&lt;Color&gt; CheeseColor { get; set; } } </code></pre> <p>Mapping:</p> <pre><code>public class ColorMapping : ComplexTypeConfiguration&lt;EnumWrapper&lt;Color&gt;&gt; { public ColorMapping() { Ignore(x =&gt; x.Enum); Property(x =&gt; x.Value); } } </code></pre> <p>I've also tried mapping it on the ChickenSandwich's EntityTypeConfiguration like this:</p> <pre><code>Property(x =&gt; x.CheeseColor.Value).HasColumnName("CheeseColor"); </code></pre> <p>If I leave it up to the ColorMapping and do no explicit mapping on the ChickenSandwichMapping, it just doesn't put it in the database. If I map it the x.CheeseColor.Value way, I get the dreaded:</p> <blockquote> <p>System.InvalidOperationException: The configured property 'CheeseColor' is not a declared property on the entity 'ChickenSandwich'. Verify that it has not been explicitly excluded from the model and that it is a valid primitive property..</p> </blockquote> <hr> <p><strong>Edit</strong></p> <p>I wasn't able to get the generic version of the enum wrapper working, so I've gone with writing individual wrappers. It's not exactly what I wanted because it violates the <a href="http://en.wikipedia.org/wiki/Don%27t_repeat_yourself">DRY</a> principle, but it does allow me to query the column as an enum. </p> <pre><code>[ComplexType] public class ColorWrapper { [NotMapped] public Color Enum { get; set; } public int Value { get { return (int)Enum; } set { Enum = (Color)value; } } public static implicit operator Color(ColorWrapper w) { if (w == null) return default(Color); return w.Enum; } public static implicit operator ColorWrapper(Color c) { return new ColorWrapper { Enum = c }; } } </code></pre> <p>I had to use the ColorWrapper on the ChickenSandwich class. It works more or less transparently. Then had to add this to my mapping class constructor to get the column name I wanted:</p> <pre><code>Property(x =&gt; x.CheeseColor.Value).HasColumnName("CheeseColorId"); </code></pre>
 

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