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POInvalidCastException - Cannot cast string to custom object even with operators
 

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  1. POInvalidCastException - Cannot cast string to custom object even with operators
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    <p>I am probably trying to do something that isn't possible. I am working with Castle.ActiveRecord / Nhibernate. I have been happy so far, but one thing I have always wanted to able to so is have something like:</p> <pre><code>[Property(ColumnType = "StringClob")] public IDictionary&lt;string, string&gt; MetaData { get; set; } </code></pre> <p>This, for obvious reasons, this isn't possible at the moment. I started playing around with things to make this work and have come down to the following.</p> <p>I have created a custom class that extends Dictionary</p> <pre><code>public class SerializableDictionary&lt;TK, TV&gt; : Dictionary&lt;TK, TV&gt; { public static explicit operator SerializableDictionary&lt;TK, TV&gt;(System.String serialized) { return JsonConvert.DeserializeObject&lt;SerializableDictionary&lt;TK, TV&gt;&gt;(serialized); } public override string ToString() { return JsonConvert.SerializeObject(this); } } </code></pre> <p>And in my ActiveRecord model I have this:</p> <pre><code>[Property(ColumnType = "StringClob")] public SerializableDictionary&lt;string, string&gt; MetaData { get; set; } </code></pre> <p>This works extremely well when I save the data. It gets serialized nicely and stores as a string. When I try to load a model though, I get the following error:</p> <pre><code>Unable to cast object of type 'System.String' to type 'MyNamespace.SerializableDictionary`2[System.String,System.String]'. </code></pre> <p>I have looked as deep as possible (using dotPeek) into where this is happening. The stack trace led me to:</p> <pre><code>NHibernate.Bytecode.Lightweight.AccessOptimizer.SetPropertyValues(Object target, Object[] values) </code></pre> <p>I am at a complete loss. I have scoured google to see if what I am trying to do is even possible. Any help is much appreciated.</p>
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    1. USShattuck
    1. USShattuck
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    1. COI'm curious, does changing it to an `implicit` operator help?
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      1. POInvalidCastException - Cannot cast string to custom object even with operators
      1. USDaniel Schilling
    2. COThanks for the comment. It doesn't unfortunately.
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      1. USShattuck
    3. CONHibernate actually generates IL code on the fly for setting properties quickly and avoiding reflection overhead. Unfortunately, the IL code it generates doesn't think to call implicit conversion operators.
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      1. POInvalidCastException - Cannot cast string to custom object even with operators
      1. USMike Christensen
 

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