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copied!<p>What you need is to build an expression tree that <a href="http://en.wikipedia.org/wiki/Language_Integrated_Query#LINQ_to_SQL" rel="noreferrer">LINQ to SQL</a> can understand. Assuming your "id" property is always named "id":</p> <pre><code>public virtual T GetById<T>(short id) { var itemParameter = Expression.Parameter(typeof(T), "item"); var whereExpression = Expression.Lambda<Func<T, bool>> ( Expression.Equal( Expression.Property( itemParameter, "id" ), Expression.Constant(id) ), new[] { itemParameter } ); var table = DB.GetTable<T>(); return table.Where(whereExpression).Single(); } </code></pre> <p>This should do the trick. It was shamelessly borrowed from <a href="http://mikehadlow.blogspot.com/2008/03/using-irepository-pattern-with-linq-to.html" rel="noreferrer">this blog</a>. This is basically what LINQ to SQL does when you write a query like</p> <pre><code>var Q = from t in Context.GetTable<T)() where t.id == id select t; </code></pre> <p>You just do the work for LTS because the compiler cannot create that for you, since nothing can enforce that T has an "id" property, and you cannot map an arbitrary "id" property from an interface to the database.</p> <p>==== UPDATE ====</p> <p>OK, here's a simple implementation for finding the primary key name, assuming there is only one (not a composite primary key), and assuming all is well type-wise (that is, your primary key is compatible with the "short" type you use in the GetById function):</p> <pre><code>public virtual T GetById<T>(short id) { var itemParameter = Expression.Parameter(typeof(T), "item"); var whereExpression = Expression.Lambda<Func<T, bool>> ( Expression.Equal( Expression.Property( itemParameter, GetPrimaryKeyName<T>() ), Expression.Constant(id) ), new[] { itemParameter } ); var table = DB.GetTable<T>(); return table.Where(whereExpression).Single(); } public string GetPrimaryKeyName<T>() { var type = Mapping.GetMetaType(typeof(T)); var PK = (from m in type.DataMembers where m.IsPrimaryKey select m).Single(); return PK.Name; } </code></pre>

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