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POC# syntax for declaring a variable of an abstract generic type
 

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    <p>I have a class defined as follows;</p> <pre><code>public abstract class Repository&lt;TEntity, TDataContext&gt; : DisposableBaseClass where TEntity : class where TDataContext : DataContext, new() {...contains Linq to SQL related functionality </code></pre> <p>In the concrete sub-class I define the types as so;</p> <pre><code>public class ConcreteRepo : Repository&lt;LSTableClass, LSDataContext&gt; </code></pre> <p>At the next tier up, I have business objects which hold the Repository object as a private variable.</p> <p>This was fine;</p> <pre><code>private ConcreteRepo _repository; </code></pre> <p>However, I then refactored this out into a parent class for all the business objects - this parent class holds the repository/ implements Dispose pattern to dispose of repository etc.</p> <p>My problem is that I just can't get the syntax right for the declaration of the variable.</p> <p>The closest I have come is;</p> <pre><code>protected Repository&lt;Object, DataContext&gt; _repository; </code></pre> <p>but this gives the compile error:</p> <p><strong>"Error 1 'System.Data.Linq.DataContext' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'TDataContext' in the generic type or method '....Repository'..."</strong></p> <p>I've tried various other things but hit other problems.</p> <p>In the business layer object inheriting this abstract class I am creating and using the _repository variable with a cast;</p> <pre><code>(Repository&lt;LSTableClass, LSDataContext&gt;)_repository = new ConcreteRepo(); </code></pre> <ul> <li>and I think this will be fine, assuming I can get this declaration right in the parent.</li> </ul> <p>If I can't get this to work I have to declare the _repository in each business object, with the full/ concrete type details, and implement the dispose pattern in each one to clear up. Not the end of the world, but I'd like to not have to.</p>
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    1. COSo am I understanding correctly that "private ConcreteRepo _repository;" is in the class you refactored? You want the class you're writing to contain this repository field *AND* be the TEntity type parameter of Repository? Exactly what you refactored is not very clear to me.
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      1. USColin Burnett
 

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