diff --git a/src/Main/Base/Project/Src/Dom/XmlDoc.cs b/src/Main/Base/Project/Src/Dom/XmlDoc.cs
index 1ff672b079..c94523ed89 100644
--- a/src/Main/Base/Project/Src/Dom/XmlDoc.cs
+++ b/src/Main/Base/Project/Src/Dom/XmlDoc.cs
@@ -8,18 +8,10 @@ namespace ICSharpCode.SharpDevelop.Dom
 	/// <summary>
 	/// Description of XmlDoc.
 	/// </summary>
-	public class XmlDoc
+	public class XmlDoc : IDisposable
 	{
 		Dictionary<string, string> xmlDescription = new Dictionary<string, string>();
-		
-		public Dictionary<string, string> XmlDescription {
-			get {
-				return xmlDescription;
-			}
-		}
-		public XmlDoc()
-		{
-		}
+		Dictionary<string, int>    indexDictionary;
 		
 		void ReadMembersSection(XmlTextReader reader)
 		{
@@ -41,6 +33,129 @@ namespace ICSharpCode.SharpDevelop.Dom
 			}
 		}
 		
+		public string GetDocumentation(string key)
+		{
+			lock (xmlDescription) {
+				if (indexDictionary != null) {
+					if (!indexDictionary.ContainsKey(key))
+						return null;
+				}
+				if (xmlDescription.ContainsKey(key))
+					return xmlDescription[key];
+				if (indexDictionary == null)
+					return null;
+				return LoadDocumentation(key);
+			}
+		}
+		
+		#region Save binary files
+		// FILE FORMAT FOR BINARY DOCUMENTATION
+		// long  magic = 0x4244636f446c6d58 (identifies file type = 'XmlDocDB')
+		// short version = 1              (file version)
+		// long  fileDate                 (last change date of xml file in DateTime ticks)
+		// int   indexPointer             (points to location where index starts in the file)
+		// { string docu }                (all documentation strings as length-prefixed strings)
+		// indexPointer points to the start of the following section:
+		// {
+		//   string key             (documentation key as length-prefixed string)
+		//   int    index           (index where the docu string starts in the file)
+		// }
+		
+		const long magic = 0x4244636f446c6d58;
+		const short version = 1;
+		
+		void Save(string fileName, DateTime fileDate)
+		{
+			using (FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.Write, FileShare.None)) {
+				using (BinaryWriter w = new BinaryWriter(fs)) {
+					w.Write(magic);
+					w.Write(version);
+					w.Write(fileDate.Ticks);
+					
+					int indexPointerPos = (int)fs.Position;
+					w.Write(0); // skip 4 bytes
+					int[] indices = new int[xmlDescription.Count];
+					
+					int i = 0;
+					foreach (KeyValuePair<string, string> p in xmlDescription) {
+						indices[i++] = (int)fs.Position;
+						w.Write(p.Value.Trim());
+					}
+					
+					int indexStart = (int)fs.Position;
+					i = 0;
+					foreach (KeyValuePair<string, string> p in xmlDescription) {
+						w.Write(p.Key);
+						w.Write(indices[i++]);
+					}
+					w.Seek(indexPointerPos, SeekOrigin.Begin);
+					w.Write(indexStart);
+				}
+			}
+		}
+		#endregion
+		
+		#region Load binary files
+		BinaryReader loader;
+		FileStream fs;
+		Queue<string> keyCacheQueue;
+		const int cacheLength = 150; // number of strings to cache when working in file-mode
+		
+		bool LoadFromBinary(string fileName, DateTime fileDate)
+		{
+			indexDictionary = new Dictionary<string, int>();
+			keyCacheQueue   = new Queue<string>(cacheLength);
+			fs = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
+			int len = (int)fs.Length;
+			loader = new BinaryReader(fs);
+			if (loader.ReadInt64() != magic) {
+				Console.WriteLine("Wrong magic");
+				return false;
+			}
+			if (loader.ReadInt16() != version) {
+				Console.WriteLine("Wrong version");
+				return false;
+			}
+			if (loader.ReadInt64() != fileDate.Ticks) {
+				Console.WriteLine("Wrong date");
+				return false;
+			}
+			fs.Position = loader.ReadInt32(); // go to start of index
+			while (fs.Position < len) {
+				string key = loader.ReadString();
+				int pos = loader.ReadInt32();
+				indexDictionary.Add(key, pos);
+			}
+			return true;
+		}
+		
+		string LoadDocumentation(string key)
+		{
+			if (keyCacheQueue.Count > cacheLength - 1) {
+				xmlDescription.Remove(keyCacheQueue.Dequeue());
+			}
+			int pos = indexDictionary[key];
+			fs.Position = pos;
+			string docu = loader.ReadString();
+			xmlDescription.Add(key, docu);
+			keyCacheQueue.Enqueue(docu);
+			return docu;
+		}
+		
+		public void Dispose()
+		{
+			if (loader != null) {
+				loader.Close();
+				fs.Close();
+			}
+			xmlDescription = null;
+			indexDictionary = null;
+			keyCacheQueue = null;
+			loader = null;
+			fs = null;
+		}
+		#endregion
+		
 		public static XmlDoc Load(TextReader textReader)
 		{
 			XmlDoc newXmlDoc = new XmlDoc();
@@ -58,11 +173,43 @@ namespace ICSharpCode.SharpDevelop.Dom
 			return newXmlDoc;
 		}
 		
+		static string MakeTempPath()
+		{
+			string tempPath = Path.Combine(Path.GetTempPath(), "SharpDevelop/DocumentationCache");
+			if (!Directory.Exists(tempPath))
+				Directory.CreateDirectory(tempPath);
+			return tempPath;
+		}
+		
 		public static XmlDoc Load(string fileName)
 		{
+			string cacheName = MakeTempPath() + "/" + Path.GetFileNameWithoutExtension(fileName)
+				+ "." + fileName.GetHashCode().ToString("x") + ".dat";
+			XmlDoc doc;
+			if (File.Exists(cacheName)) {
+				doc = new XmlDoc();
+				if (doc.LoadFromBinary(cacheName, File.GetLastWriteTimeUtc(fileName))) {
+					return doc;
+				} else {
+					doc.Dispose();
+					try {
+						File.Delete(cacheName);
+					} catch {}
+				}
+			}
+			
 			using (TextReader textReader = File.OpenText(fileName)) {
-				return Load(textReader);
+				doc = Load(textReader);
+			}
+			
+			if (doc.xmlDescription.Count > cacheLength * 2) {
+				DateTime date = File.GetLastWriteTimeUtc(fileName);
+				doc.Save(cacheName, date);
+				doc.Dispose();
+				doc = new XmlDoc();
+				doc.LoadFromBinary(cacheName, date);
 			}
+			return doc;
 		}
 	}
 }
diff --git a/src/Main/Base/Project/Src/Services/ParserService/CaseSensitiveProjectContent.cs b/src/Main/Base/Project/Src/Services/ParserService/CaseSensitiveProjectContent.cs
index 4ae1d1fa6d..e2c9331257 100644
--- a/src/Main/Base/Project/Src/Services/ParserService/CaseSensitiveProjectContent.cs
+++ b/src/Main/Base/Project/Src/Services/ParserService/CaseSensitiveProjectContent.cs
@@ -94,12 +94,14 @@ namespace ICSharpCode.Core
 		
 		public string GetXmlDocumentation(string memberTag)
 		{
-			if (xmlDoc.XmlDescription.ContainsKey(memberTag)) {
-				return xmlDoc.XmlDescription[memberTag];
+			string desc = xmlDoc.GetDocumentation(memberTag);
+			if (desc != null) {
+				return desc;
 			}
 			foreach (IProjectContent referencedContent in referencedContents) {
-				if (referencedContent.XmlDoc.XmlDescription.ContainsKey(memberTag)) {
-					return referencedContent.XmlDoc.XmlDescription[memberTag];
+				desc = referencedContent.XmlDoc.GetDocumentation(memberTag);
+				if (desc != null) {
+					return desc;
 				}
 			}
 			return null;
@@ -263,6 +265,7 @@ namespace ICSharpCode.Core
 		
 		public void Dispose()
 		{
+			xmlDoc.Dispose();
 			ProjectService.ReferenceAdded -= OnReferenceAdded;
 			initializing = false;
 		}
diff --git a/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs b/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs
index 68c1f4d22a..a60f03de0b 100644
--- a/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs
+++ b/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs
@@ -24,7 +24,7 @@ namespace ICSharpCode.Core
 {
 	public class ProjectContentRegistry
 	{
-		static Dictionary<string, IProjectContent> contents = new Dictionary<string, IProjectContent>();
+		static Dictionary<string, IProjectContent> contents = new Dictionary<string, IProjectContent>(StringComparer.InvariantCultureIgnoreCase);
 		
 		public static IProjectContent GetMscorlibContent()
 		{