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copied!<p><strong>UPDATE:</strong> I've finally got this working the right way, please see below.</p> <p><code>DynamicMethod</code> builds a method dynamically at runtime; in the library you are using the method that is created is being added to the object <code>T</code>; however, when <code>T</code> is an interface this fails because you cannot add a method to an interface.</p> <p>The main problem is in the method:</p> <p><code>private static GetPropertyDelegate BuildGetPropertyMethod(PropertyInfo pi)</code></p> <p>as the way this was written it will only work when the collection type <code>T</code> is concrete.</p> <p>If you change the implementation to:</p> <pre><code>private static GetPropertyDelegate BuildGetPropertyMethod(PropertyInfo pi) { MethodInfo getMethod = pi.GetGetMethod(); Debug.Assert(getMethod != null); DynamicMethod dm = new DynamicMethod( "GetProperty_" + typeof(T).Name + "_" + pi.Name, typeof(object), new Type[] { typeof(T) }, pi.Module, true); ILGenerator il = dm.GetILGenerator(); il.Emit(OpCodes.Ldarg_0); il.EmitCall(OpCodes.Callvirt, getMethod, null); if (pi.PropertyType.IsValueType) { il.Emit(OpCodes.Box, pi.PropertyType); } // Return the result of the comparison. il.Emit(OpCodes.Ret); return (GetPropertyDelegate)dm.CreateDelegate(typeof(GetPropertyDelegate)); } </code></pre> <p><a href="http://web.archive.org/web/20121028071433/https://www.codingday.com/reflection-for-properties-and-fields-with-dynamicmethod/" rel="nofollow noreferrer">it will work for both concrete types and interfaces</a>.</p> <p>You also need to update the following two methods:</p> <p><code>private static Comparison<T> BuildValueTypeComparison(PropertyInfo pi, ListSortDirection direction)</code></p> <p><code>private static Comparison<T> BuildNullableComparison(PropertyInfo pi, ListSortDirection direction)</code></p> <p>I might be wrong, but I think that the speed gain achieved in these methods comes from the fast property read, so there is not really that much benefit from writing the whole methods using the <code>DynamicMethod</code> method; we can just reuse the <code>BuildGetPropertyMethod</code> from above. So doing this, these become:</p> <pre><code>private static Comparison<T> BuildValueTypeComparison( PropertyInfo pi, ListSortDirection direction) { GetPropertyDelegate m = BuildGetPropertyMethod(pi); Comparison<T> d = delegate(T x, T y) { object mx = m(x); object my = m(y); IComparable c = (IComparable)mx; if (direction == ListSortDirection.Descending) { return -c.CompareTo(my); } return c.CompareTo(my); }; return d; } private static Comparison<T> BuildNullableComparison( PropertyInfo pi, ListSortDirection direction) { GetPropertyDelegate m = BuildGetPropertyMethod(pi); Comparison<T> d = delegate(T x, T y) { object mx = m(x); object my = m(y); IComparable c = (IComparable)mx; if (c == null) { c = (IComparable)my; if (c == null) { return 0; } return direction == ListSortDirection.Descending ? c.CompareTo(mx) : -c.CompareTo(mx); } return direction == ListSortDirection.Descending ? -c.CompareTo(my) : c.CompareTo(my); }; return d; } </code></pre> <p>Obviously do some testing on it, but I'm pretty sure that is what you want and it should be about as fast as the previous code.</p>

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