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PO.NET Dapper nullable cast error
 

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    <p>Using .NET Dapper, I am having an issue getting a database field that contains an integer value (0/1) to map to a nullable boolean property in a class.</p> <p>To keep things simple, I have stripped down and renamed the class to the bare minimum needed to reproduce the problem:</p> <pre><code>public class Test { public bool? TestField { get; set; } } </code></pre> <p>If the following code is called to populate the Test class:</p> <pre><code>var Results = DBConnection.Query&lt;Test&gt;("SELECT 0 As TestField]").ToList(); </code></pre> <p>the following error will be thrown:</p> <pre><code>Invalid cast from 'System.Int32' to 'System.Nullable`1[[System.Boolean, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] </code></pre> <p>If I remove the question mark, making the field a non-nullable boolean (i.e. public <strong>bool</strong> TestField), everything works fine.</p> <p>The immediate answer might appear to remove the nullable and call it a day. However, the reason that won't work is because we are using this same class to serialize records to and from a web service, and we need to be able to tell the difference between false and null. I thought of having two classes, one with nullable property types, and one without, but then I have the added overhead of maintaining two classes instead of one.</p> <p>A custom data transformation during a property set would be ideal. Though, I haven't found anything in the dapper documentation to suggest that this is even possible.</p>
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