filter.cs

摄像管理系统

namespace dshow
{
	using System;
	using System.Runtime.InteropServices;
	using dshow.Core;

	/// <summary>
	/// Summary description for Filter.
	/// </summary>
	public class Filter : IComparable
	{
		// Device name
		public readonly string Name;

		// Moniker string
		public readonly string MonikerString;

		// Create new filter from moneker`s string
		public Filter(string monikerString)
		{
			MonikerString = monikerString;
			Name = GetName(monikerString);
		}

		// Create new filter from it's Moniker
		internal Filter(UCOMIMoniker moniker)
		{
			MonikerString = GetMonikerString(moniker);
			Name = GetName(moniker);
		}


		// Get moniker string of the moniker
		private string GetMonikerString(UCOMIMoniker moniker)
		{
			string str;
			moniker.GetDisplayName(null, null, out str);
			return str;
		}

		// Get filter name represented by the moniker
		private string GetName(UCOMIMoniker moniker)
		{
			Object			bagObj = null;
			IPropertyBag	bag = null;

			try
			{
				Guid bagId = typeof(IPropertyBag).GUID;
				// get property bag of the moniker
				moniker.BindToStorage(null, null, ref bagId, out bagObj);
				bag = (IPropertyBag) bagObj;

				// read FriendlyName
				object val = "";
				int hr = bag.Read("FriendlyName", ref val, IntPtr.Zero);
				if (hr != 0)
					Marshal.ThrowExceptionForHR(hr);

				// get it as string
				string ret = val as string;
				if ((ret == null) || (ret.Length < 1))
					throw new ApplicationException();

				return ret;
			}	
			catch (Exception)
			{
				return "";
			}
			finally
			{
				// release all COM objects
				bag = null;
				if (bagObj != null)
				{
					Marshal.ReleaseComObject(bagObj);
					bagObj = null;
				}
			}
		}

		// Get filter name represented by the moniker string
		private string GetName(string monikerString)
		{
			UCOMIBindCtx bindCtx = null;
			UCOMIMoniker moniker = null;
			String name = "";
			int n = 0;

			// create bind context
			if (Win32.CreateBindCtx(0, out bindCtx) == 0)
			{
				// convert moniker`s string to a moniker
				if (Win32.MkParseDisplayName(bindCtx, monikerString, ref n, out moniker) == 0)
				{
					// get device name
					name = GetName(moniker);

					Marshal.ReleaseComObject(moniker);
					moniker = null;
				}
				Marshal.ReleaseComObject(bindCtx);
				bindCtx = null;
			}
			return name;
		}

		// Compares objects of the type
		public int CompareTo(object obj)
		{
			if (obj == null)
				return 1;

			Filter f = (Filter) obj;
			return (this.Name.CompareTo(f.Name));
		}
	}
}