How do I use reflection to get properties explicitly implementing an interface?

Question

I think the class you are looking for is System.Reflection.InterfaceMapping.

Type ifaceType = typeof(TempInterface);
Type tempType = typeof(TempClass);
InterfaceMapping map = tempType.GetInterfaceMap(ifaceType);
for (int i = 0; i < map.InterfaceMethods.Length; i++)
{
    MethodInfo ifaceMethod = map.InterfaceMethods[i];
    MethodInfo targetMethod = map.TargetMethods[i];
    Debug.WriteLine(String.Format("{0} maps to {1}", ifaceMethod, targetMethod));
}

The property getter and setter of an explicitly implemented interface property has an unusual attribute. It's IsFinal property is True, even when it is not a member of a sealed class. Try this code to verify my assertion:

  foreach (AssemblyName name in Assembly.GetEntryAssembly().GetReferencedAssemblies()) {
    Assembly asm = Assembly.Load(name);
    foreach (Type t in asm.GetTypes()) {
      if (t.IsAbstract) continue;
      foreach (MethodInfo mi in t.GetMethods(BindingFlags.NonPublic | BindingFlags.Instance)) {
        int dot = mi.Name.LastIndexOf('.');
        string s = mi.Name.Substring(dot + 1);
        if (!s.StartsWith("get_") && !s.StartsWith("set_")) continue;
        if (mi.IsFinal)
          Console.WriteLine(mi.Name);
      }
    }
  }

Here's a modified solution based on the implementation given in this blog post:

var explicitProperties =
    from prop in typeof(TempClass).GetProperties(
        BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly)
    let getAccessor = prop.GetGetMethod(true)
    where getAccessor.IsFinal && getAccessor.IsPrivate
    select prop;

foreach (var p in explicitProperties)
    Console.WriteLine(p.Name);

Building on the answer by MrKurt:

var targetMethods =
    from iface in typeof(TempClass).GetInterfaces()
    from method in typeof(TempClass).GetInterfaceMap(iface).TargetMethods
    select method;

var explicitProps =
    from prop in typeof(TempClass).GetProperties(BindingFlags.Instance |
                                                 BindingFlags.NonPublic)
    where targetMethods.Contains(prop.GetGetMethod(true)) ||
          targetMethods.Contains(prop.GetSetMethod(true))
    select prop;

I had to modify Jacob Carpenter's answer but it works nicely. nobugz's also works but Jacobs is more compact.

var explicitProperties =
from method in typeof(TempClass).GetMethods(BindingFlags.NonPublic | BindingFlags.Instance)
where method.IsFinal && method.IsPrivate
select method;

A simple helper class that could help:

public class InterfacesPropertiesMap
{
    private readonly Dictionary<Type, PropertyInfo[]> map;

    public InterfacesPropertiesMap(Type type)
    {
        this.Interfaces = type.GetInterfaces();
        var properties = type.GetProperties(BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public);

        this.map = new Dictionary<Type, PropertyInfo[]>(this.Interfaces.Length);

        foreach (var intr in this.Interfaces)
        {
            var interfaceMap = type.GetInterfaceMap(intr);
            this.map.Add(intr, properties.Where(p => interfaceMap.TargetMethods
                                                    .Any(t => t == p.GetGetMethod(true) ||
                                                              t == p.GetSetMethod(true)))
                                         .Distinct().ToArray());
        }
    }

    public Type[] Interfaces { get; private set; }

    public PropertyInfo[] this[Type interfaceType]
    {
        get { return this.map[interfaceType]; }
    }
}

You'll get properties for each interface, even explicitly implemented.