rework dlna project

RSSDP/SsdpDeviceExtensions.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Rssdp
+{
+	/// <summary>
+	/// Extensions for <see cref="SsdpDevice"/> and derived types.
+	/// </summary>
+	public static class SsdpDeviceExtensions
+	{
+
+		/// <summary>
+		/// Returns the root device associated with a device instance derived from <see cref="SsdpDevice"/>.
+		/// </summary>
+		/// <param name="device">The device instance to find the <see cref="SsdpRootDevice"/> for.</param>
+		/// <remarks>
+		/// <para>The <paramref name="device"/> must be or inherit from <see cref="SsdpRootDevice"/> or <see cref="SsdpEmbeddedDevice"/>, otherwise an <see cref="System.InvalidCastException"/> will occur.</para>
+		/// <para>May return null if the <paramref name="device"/> instance is an embedded device not yet associated with a <see cref="SsdpRootDevice"/> instance yet.</para>
+		/// <para>If <paramref name="device"/> is an instance of <see cref="SsdpRootDevice"/> (or derives from it), returns the same instance cast to <see cref="SsdpRootDevice"/>.</para>
+		/// </remarks>
+		/// <returns>The <see cref="SsdpRootDevice"/> instance associated with the device instance specified, or null otherwise.</returns>
+		/// <exception cref="System.ArgumentNullException">Thrown if <paramref name="device"/> is null.</exception>
+		/// <exception cref="System.InvalidCastException">Thrown if <paramref name="device"/> is not an instance of or dervied from either <see cref="SsdpRootDevice"/> or <see cref="SsdpEmbeddedDevice"/>.</exception>
+		public static SsdpRootDevice ToRootDevice(this SsdpDevice device)
+		{
+			if (device == null) throw new System.ArgumentNullException("device");
+
+			var rootDevice = device as SsdpRootDevice;
+			if (rootDevice == null)
+				rootDevice = ((SsdpEmbeddedDevice)device).RootDevice;
+
+			return rootDevice;
+		}
+	}
+}