diff --git a/src/Libraries/ICSharpCode.TextEditor/Project/Src/Actions/FoldActions.cs b/src/Libraries/ICSharpCode.TextEditor/Project/Src/Actions/FoldActions.cs
index 47dbdc610b..1f6643836f 100644
--- a/src/Libraries/ICSharpCode.TextEditor/Project/Src/Actions/FoldActions.cs
+++ b/src/Libraries/ICSharpCode.TextEditor/Project/Src/Actions/FoldActions.cs
@@ -9,15 +9,29 @@ using System;
 using System.Collections.Generic;
 using ICSharpCode.TextEditor.Document;
 
-namespace ICSharpCode.TextEditor.Actions 
+namespace ICSharpCode.TextEditor.Actions
 {
 	public class ToggleFolding : AbstractEditAction
 	{
 		public override void Execute(TextArea textArea)
 		{
 			List<FoldMarker> foldMarkers = textArea.Document.FoldingManager.GetFoldingsWithStart(textArea.Caret.Line);
-			foreach (FoldMarker fm in foldMarkers) {
-				fm.IsFolded = !fm.IsFolded;
+			if (foldMarkers.Count != 0) {
+				foreach (FoldMarker fm in foldMarkers)
+					fm.IsFolded = !fm.IsFolded;
+			} else {
+				foldMarkers = textArea.Document.FoldingManager.GetFoldingsContainsLineNumber(textArea.Caret.Line);
+				if (foldMarkers.Count != 0) {
+					FoldMarker innerMost = foldMarkers[0];
+					for (int i = 1; i < foldMarkers.Count; i++) {
+						if (new TextLocation(foldMarkers[i].StartColumn, foldMarkers[i].StartLine) >
+						    new TextLocation(innerMost.StartColumn, innerMost.StartLine))
+						{
+							innerMost = foldMarkers[i];
+						}
+					}
+					innerMost.IsFolded = !innerMost.IsFolded;
+				}
 			}
 			textArea.Document.FoldingManager.NotifyFoldingsChanged(EventArgs.Empty);
 		}
diff --git a/src/Libraries/NRefactory/Project/NRefactory.csproj b/src/Libraries/NRefactory/Project/NRefactory.csproj
index 0b1dfee10c..fa7e95ad27 100644
--- a/src/Libraries/NRefactory/Project/NRefactory.csproj
+++ b/src/Libraries/NRefactory/Project/NRefactory.csproj
@@ -55,6 +55,7 @@
     <None Include="Src\Lexer\BuildKeywords.pl" />
     <Compile Include="Configuration\AssemblyInfo.cs" />
     <Compile Include="Src\Lexer\AbstractLexer.cs" />
+    <Compile Include="Src\Lexer\CSharp\ConditionalCompilation.cs" />
     <Compile Include="Src\Lexer\CSharp\Keywords.cs" />
     <Compile Include="Src\Lexer\CSharp\Lexer.cs" />
     <Compile Include="Src\Lexer\CSharp\Tokens.cs" />
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs b/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs
index 1fc7d608a5..a5f62b1508 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs
@@ -40,15 +40,10 @@ namespace ICSharpCode.NRefactory.Parser
 		// used for the original value of strings (with escape sequences).
 		protected StringBuilder originalValue = new StringBuilder();
 		
-		bool skipAllComments = false;
-		
-		public bool SkipAllComments {
-			get {
-				return skipAllComments;
-			}
-			set {
-				skipAllComments = value;
-			}
+		public bool SkipAllComments { get; set; }
+		public bool EvaluateConditionalCompilation { get; set; }
+		public virtual IDictionary<string, object> ConditionalCompilationSymbols { 
+			get { throw new NotSupportedException(); }
 		}
 		
 		protected int Line {
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/CSharp/ConditionalCompilation.cs b/src/Libraries/NRefactory/Project/Src/Lexer/CSharp/ConditionalCompilation.cs
new file mode 100644
index 0000000000..3b45a985c3
--- /dev/null
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/CSharp/ConditionalCompilation.cs
@@ -0,0 +1,90 @@
+// <file>
+//     <copyright see="prj:///doc/copyright.txt"/>
+//     <license see="prj:///doc/license.txt"/>
+//     <owner name="Daniel Grunwald"/>
+//     <version>$Revision$</version>
+// </file>
+
+using System;
+using System.Collections.Generic;
+using ICSharpCode.NRefactory.Ast;
+using ICSharpCode.NRefactory.Visitors;
+
+namespace ICSharpCode.NRefactory.Parser.CSharp
+{
+	sealed class ConditionalCompilation : AbstractAstVisitor
+	{
+		static readonly object SymbolDefined = new object();
+		Dictionary<string, object> symbols = new Dictionary<string, object>();
+		
+		public IDictionary<string, object> Symbols { 
+			get { return symbols; }
+		}
+		
+		public void Define(string symbol)
+		{
+			symbols[symbol] = SymbolDefined;
+		}
+		
+		public void Undefine(string symbol)
+		{
+			symbols.Remove(symbol);
+		}
+		
+		public bool Evaluate(Expression condition)
+		{
+			return condition.AcceptVisitor(this, null) == SymbolDefined;
+		}
+		
+		public override object VisitPrimitiveExpression(PrimitiveExpression primitiveExpression, object data)
+		{
+			if (primitiveExpression.Value is bool)
+				return (bool)primitiveExpression.Value ? SymbolDefined : null;
+			else
+				return null;
+		}
+		
+		public override object VisitIdentifierExpression(IdentifierExpression identifierExpression, object data)
+		{
+			return symbols.ContainsKey(identifierExpression.Identifier) ? SymbolDefined : null;
+		}
+		
+		public override object VisitUnaryOperatorExpression(UnaryOperatorExpression unaryOperatorExpression, object data)
+		{
+			if (unaryOperatorExpression.Op == UnaryOperatorType.Not) {
+				return unaryOperatorExpression.Expression.AcceptVisitor(this, data) == SymbolDefined ? null : SymbolDefined;
+			} else {
+				return null;
+			}
+		}
+		
+		public override object VisitBinaryOperatorExpression(BinaryOperatorExpression binaryOperatorExpression, object data)
+		{
+			bool lhs = binaryOperatorExpression.Left.AcceptVisitor(this, data) == SymbolDefined;
+			bool rhs = binaryOperatorExpression.Right.AcceptVisitor(this, data) == SymbolDefined;
+			bool result;
+			switch (binaryOperatorExpression.Op) {
+				case BinaryOperatorType.LogicalAnd:
+					result = lhs && rhs;
+					break;
+				case BinaryOperatorType.LogicalOr:
+					result = lhs || rhs;
+					break;
+				case BinaryOperatorType.Equality:
+					result = lhs == rhs;
+					break;
+				case BinaryOperatorType.InEquality:
+					result = lhs != rhs;
+					break;
+				default:
+					return null;
+			}
+			return result ? SymbolDefined : null;
+		}
+		
+		public override object VisitParenthesizedExpression(ParenthesizedExpression parenthesizedExpression, object data)
+		{
+			return parenthesizedExpression.Expression.AcceptVisitor(this, data);
+		}
+	}
+}
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/CSharp/Lexer.cs b/src/Libraries/NRefactory/Project/Src/Lexer/CSharp/Lexer.cs
index 477eeb23b8..503bb97786 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/CSharp/Lexer.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/CSharp/Lexer.cs
@@ -6,6 +6,7 @@
 // </file>
 
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Text;
@@ -18,20 +19,6 @@ namespace ICSharpCode.NRefactory.Parser.CSharp
 		{
 		}
 		
-		void ReadPreProcessingDirective()
-		{
-			Location start = new Location(Col - 1, Line);
-			
-			// skip spaces between # and the directive
-			while (ReaderPeek() == ' ')
-				ReaderRead();
-			
-			bool canBeKeyword;
-			string directive = ReadIdent('#', out canBeKeyword);
-			string argument  = ReadToEndOfLine();
-			this.specialTracker.AddPreprocessingDirective(directive, argument.Trim(), start, new Location(start.X + directive.Length + argument.Length, start.Y));
-		}
-		
 		protected override Token Next()
 		{
 			int nextChar;
@@ -974,5 +961,211 @@ namespace ICSharpCode.NRefactory.Parser.CSharp
 			}
 			curToken = new Token(Tokens.EOF, Col, Line);
 		}
+		
+		public override IDictionary<string, object> ConditionalCompilationSymbols {
+			get { return conditionalCompilation.Symbols; }
+		}
+		
+		ConditionalCompilation conditionalCompilation = new ConditionalCompilation();
+		
+		void ReadPreProcessingDirective()
+		{
+			PreprocessingDirective d = ReadPreProcessingDirectiveInternal(true, true);
+			this.specialTracker.AddPreprocessingDirective(d);
+			
+			if (EvaluateConditionalCompilation) {
+				switch (d.Cmd) {
+					case "#define":
+						conditionalCompilation.Define(d.Arg);
+						break;
+					case "#undef":
+						conditionalCompilation.Undefine(d.Arg);
+						break;
+					case "#if":
+						if (!conditionalCompilation.Evaluate(d.Expression)) {
+							// skip to valid #elif or #else or #endif
+							int level = 1;
+							while (true) {
+								d = SkipToPreProcessingDirective(false, level == 1);
+								if (d == null)
+									break;
+								if (d.Cmd == "#if") {
+									level++;
+								} else if (d.Cmd == "#endif") {
+									level--;
+									if (level == 0)
+										break;
+								} else if (level == 1 &&  (d.Cmd == "#else"
+								                           || d.Cmd == "#elif" && conditionalCompilation.Evaluate(d.Expression)))
+								{
+									break;
+								}
+							}
+							if (d != null)
+								this.specialTracker.AddPreprocessingDirective(d);
+						}
+						break;
+					case "#elif":
+					case "#else":
+						// we already visited the #if part or a previous #elif part, so skip until #endif
+						{
+							int level = 1;
+							while (true) {
+								d = SkipToPreProcessingDirective(false, false);
+								if (d == null)
+									break;
+								if (d.Cmd == "#if") {
+									level++;
+								} else if (d.Cmd == "#endif") {
+									level--;
+									if (level == 0)
+										break;
+								}
+							}
+							if (d != null)
+								this.specialTracker.AddPreprocessingDirective(d);
+						}
+						break;
+				}
+			}
+		}
+		
+		PreprocessingDirective SkipToPreProcessingDirective(bool parseIfExpression, bool parseElifExpression)
+		{
+			int c;
+			while (true) {
+				PPWhitespace();
+				c = ReaderRead();
+				if (c == -1) {
+					errors.Error(Line, Col, String.Format("Reached EOF but expected #endif"));
+					return null;
+				} else if (c == '#') {
+					break;
+				} else {
+					SkipToEndOfLine();
+				}
+			}
+			return ReadPreProcessingDirectiveInternal(parseIfExpression, parseElifExpression);
+		}
+		
+		PreprocessingDirective ReadPreProcessingDirectiveInternal(bool parseIfExpression, bool parseElifExpression)
+		{
+			Location start = new Location(Col - 1, Line);
+			
+			// skip spaces between # and the directive
+			PPWhitespace();
+			
+			bool canBeKeyword;
+			string directive = ReadIdent('#', out canBeKeyword);
+			
+			PPWhitespace();
+			if (parseIfExpression && directive == "#if" || parseElifExpression && directive == "#elif") {
+				Ast.Expression expr = PPExpression();
+				int c = ReaderRead();
+				if (c >= 0 && !HandleLineEnd((char)c)) {
+					if (c == '/' && ReaderRead() == '/') {
+						// comment to end of line
+					} else {
+						errors.Error(Col, Line, "Expected end of line");
+					}
+					SkipToEndOfLine(); // skip comment
+				}
+				return new PreprocessingDirective(directive, null, start, new Location(Col, Line)) { Expression = expr };
+			} else {
+				string arg = ReadToEndOfLine();
+				int pos = arg.IndexOf("//");
+				if (pos >= 0)
+					arg = arg.Substring(0, pos);
+				arg = arg.Trim();
+				return new PreprocessingDirective(directive, arg, start, new Location(Col, Line));
+			}
+		}
+		
+		void PPWhitespace()
+		{
+			while (ReaderPeek() == ' ' || ReaderPeek() == '\t')
+				ReaderRead();
+		}
+		
+		Ast.Expression PPExpression()
+		{
+			Ast.Expression expr = PPAndExpression();
+			while (ReaderPeek() == '|') {
+				Token token = ReadOperator((char)ReaderRead());
+				if (token == null || token.kind != Tokens.LogicalOr) {
+					return expr;
+				}
+				Ast.Expression expr2 = PPAndExpression();
+				expr = new Ast.BinaryOperatorExpression(expr, Ast.BinaryOperatorType.LogicalOr, expr2);
+			}
+			return expr;
+		}
+		
+		Ast.Expression PPAndExpression()
+		{
+			Ast.Expression expr = PPEqualityExpression();
+			while (ReaderPeek() == '&') {
+				Token token = ReadOperator((char)ReaderRead());
+				if (token == null || token.kind != Tokens.LogicalAnd) {
+					break;
+				}
+				Ast.Expression expr2 = PPEqualityExpression();
+				expr = new Ast.BinaryOperatorExpression(expr, Ast.BinaryOperatorType.LogicalAnd, expr2);
+			}
+			return expr;
+		}
+		
+		Ast.Expression PPEqualityExpression()
+		{
+			Ast.Expression expr = PPUnaryExpression();
+			while (ReaderPeek() == '=' || ReaderPeek() == '!') {
+				Token token = ReadOperator((char)ReaderRead());
+				if (token == null || token.kind != Tokens.Equals && token.kind != Tokens.NotEqual) {
+					break;
+				}
+				Ast.Expression expr2 = PPUnaryExpression();
+				expr = new Ast.BinaryOperatorExpression(expr, token.kind == Tokens.Equals ? Ast.BinaryOperatorType.Equality : Ast.BinaryOperatorType.InEquality, expr2);
+			}
+			return expr;
+		}
+		
+		Ast.Expression PPUnaryExpression()
+		{
+			PPWhitespace();
+			if (ReaderPeek() == '!') {
+				ReaderRead();
+				PPWhitespace();
+				return new Ast.UnaryOperatorExpression(PPUnaryExpression(), Ast.UnaryOperatorType.Not);
+			} else {
+				return PPPrimaryExpression();
+			}
+		}
+		
+		Ast.Expression PPPrimaryExpression()
+		{
+			int c = ReaderRead();
+			if (c < 0)
+				return Ast.Expression.Null;
+			if (c == '(') {
+				Ast.Expression expr = new Ast.ParenthesizedExpression(PPExpression());
+				PPWhitespace();
+				if (ReaderRead() != ')')
+					errors.Error(Col, Line, "Expected ')'");
+				PPWhitespace();
+				return expr;
+			} else {
+				if (c != '_' && !char.IsLetterOrDigit((char)c) && c != '\\')
+					errors.Error(Col, Line, "Expected conditional symbol");
+				bool canBeKeyword;
+				string symbol = ReadIdent((char)c, out canBeKeyword);
+				PPWhitespace();
+				if (canBeKeyword && symbol == "true")
+					return new Ast.PrimitiveExpression(true, "true");
+				else if (canBeKeyword && symbol == "false")
+					return new Ast.PrimitiveExpression(false, "false");
+				else
+					return new Ast.IdentifierExpression(symbol);
+			}
+		}
 	}
 }
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/ILexer.cs b/src/Libraries/NRefactory/Project/Src/Lexer/ILexer.cs
index f27f0f6d70..ab647b75f6 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/ILexer.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/ILexer.cs
@@ -50,6 +50,17 @@ namespace ICSharpCode.NRefactory.Parser
 			set;
 		}
 		
+		/// <summary>
+		/// Gets/Sets if the lexer should evaluate conditional compilation symbols.
+		/// </summary>
+		bool EvaluateConditionalCompilation { get; set; }
+		
+		/// <summary>
+		/// The dictionary with the conditional compilation symbols.
+		/// C# ignores the value (you can use null), it just cares whether a symbol is defined.
+		/// </summary>
+		IDictionary<string, object> ConditionalCompilationSymbols { get; }
+		
 		/// <summary>
 		/// Returns the comments that had been read and containing tag key words.
 		/// </summary>
@@ -75,7 +86,7 @@ namespace ICSharpCode.NRefactory.Parser
 		/// <returns>An <see cref="Token"/> object.</returns>
 		Token NextToken();
 		
-				/// <summary>
+		/// <summary>
 		/// Skips to the end of the current code block.
 		/// For this, the lexer must have read the next token AFTER the token opening the
 		/// block (so that Lexer.Token is the block-opening token, not Lexer.LookAhead).
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/Special/ISpecial.cs b/src/Libraries/NRefactory/Project/Src/Lexer/Special/ISpecial.cs
index 5e83522c62..b610828384 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/Special/ISpecial.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/Special/ISpecial.cs
@@ -32,37 +32,20 @@ namespace ICSharpCode.NRefactory
 	{
 		public abstract object AcceptVisitor(ISpecialVisitor visitor, object data);
 		
-		Location startPosition, endPosition;
-		
 		protected AbstractSpecial(Location position)
 		{
-			this.startPosition = position;
-			this.endPosition = position;
+			this.StartPosition = position;
+			this.EndPosition = position;
 		}
 		
 		protected AbstractSpecial(Location startPosition, Location endPosition)
 		{
-			this.startPosition = startPosition;
-			this.endPosition = endPosition;
-		}
-		
-		public Location StartPosition {
-			get {
-				return startPosition;
-			}
-			set {
-				startPosition = value;
-			}
+			this.StartPosition = startPosition;
+			this.EndPosition = endPosition;
 		}
 		
-		public Location EndPosition {
-			get {
-				return endPosition;
-			}
-			set {
-				endPosition = value;
-			}
-		}
+		public Location StartPosition { get; set; }
+		public Location EndPosition { get; set; }
 		
 		public override string ToString()
 		{
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/Special/PreProcessingDirective.cs b/src/Libraries/NRefactory/Project/Src/Lexer/Special/PreProcessingDirective.cs
index e69f046c66..36db0236c3 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/Special/PreProcessingDirective.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/Special/PreProcessingDirective.cs
@@ -12,6 +12,7 @@ namespace ICSharpCode.NRefactory
 {
 	public class PreprocessingDirective : AbstractSpecial
 	{
+		#region Conversion C# <-> VB
 		public static void VBToCSharp(IList<ISpecial> list)
 		{
 			for (int i = 0; i < list.Count; ++i) {
@@ -78,10 +79,15 @@ namespace ICSharpCode.NRefactory
 			}
 			return new PreprocessingDirective(cmd, arg, dir.StartPosition, dir.EndPosition);
 		}
+		#endregion
 		
 		string cmd;
 		string arg;
+		Ast.Expression expression = Ast.Expression.Null;
 		
+		/// <summary>
+		/// Gets the directive name, including '#'.
+		/// </summary>
 		public string Cmd {
 			get {
 				return cmd;
@@ -91,6 +97,9 @@ namespace ICSharpCode.NRefactory
 			}
 		}
 		
+		/// <summary>
+		/// Gets the directive argument.
+		/// </summary>
 		public string Arg {
 			get {
 				return arg;
@@ -100,6 +109,14 @@ namespace ICSharpCode.NRefactory
 			}
 		}
 		
+		/// <summary>
+		/// Gets/sets the expression (for directives that take an expression, e.g. #if and #elif).
+		/// </summary>
+		public Ast.Expression Expression {
+			get { return expression; }
+			set { expression = value ?? Ast.Expression.Null; }
+		}
+		
 		public override string ToString()
 		{
 			return String.Format("[PreProcessingDirective: Cmd = {0}, Arg = {1}]",
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/Special/SpecialTracker.cs b/src/Libraries/NRefactory/Project/Src/Lexer/Special/SpecialTracker.cs
index 6cd4a35431..9fce36116b 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/Special/SpecialTracker.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/Special/SpecialTracker.cs
@@ -45,9 +45,11 @@ namespace ICSharpCode.NRefactory.Parser
 			currentSpecials.Add(new BlankLine(point));
 		}
 		
-		public void AddPreprocessingDirective(string cmd, string arg, Location start, Location end)
+		public void AddPreprocessingDirective(PreprocessingDirective directive)
 		{
-			currentSpecials.Add(new PreprocessingDirective(cmd, arg, start, end));
+			if (directive == null)
+				throw new ArgumentNullException("directive");
+			currentSpecials.Add(directive);
 		}
 		
 		// used for comment tracking
diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/VBNet/Lexer.cs b/src/Libraries/NRefactory/Project/Src/Lexer/VBNet/Lexer.cs
index a4dce1f6e0..e3f27d8d6c 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/VBNet/Lexer.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/VBNet/Lexer.cs
@@ -480,7 +480,7 @@ namespace ICSharpCode.NRefactory.Parser.VB
 			Location start = new Location(Col - 1, Line);
 			string directive = ReadIdent('#');
 			string argument  = ReadToEndOfLine();
-			this.specialTracker.AddPreprocessingDirective(directive, argument.Trim(), start, new Location(start.X + directive.Length + argument.Length, start.Y));
+			this.specialTracker.AddPreprocessingDirective(new PreprocessingDirective(directive, argument.Trim(), start, new Location(start.X + directive.Length + argument.Length, start.Y)));
 		}
 		
 		string ReadDate()
diff --git a/src/Libraries/NRefactory/Project/Src/PrettyPrinter/AbstractOutputFormatter.cs b/src/Libraries/NRefactory/Project/Src/PrettyPrinter/AbstractOutputFormatter.cs
index 7d89ab1062..e017b00eb9 100644
--- a/src/Libraries/NRefactory/Project/Src/PrettyPrinter/AbstractOutputFormatter.cs
+++ b/src/Libraries/NRefactory/Project/Src/PrettyPrinter/AbstractOutputFormatter.cs
@@ -184,7 +184,11 @@ namespace ICSharpCode.NRefactory.PrettyPrinter
 		
 		public virtual void PrintPreprocessingDirective(PreprocessingDirective directive, bool forceWriteInPreviousBlock)
 		{
-			if (string.IsNullOrEmpty(directive.Arg))
+			if (!directive.Expression.IsNull) {
+				CSharpOutputVisitor visitor = new CSharpOutputVisitor();
+				directive.Expression.AcceptVisitor(visitor, null);
+				WriteLineInPreviousLine(directive.Cmd + " " + visitor.Text, forceWriteInPreviousBlock);
+			} else if (string.IsNullOrEmpty(directive.Arg))
 				WriteLineInPreviousLine(directive.Cmd, forceWriteInPreviousBlock);
 			else
 				WriteLineInPreviousLine(directive.Cmd + " " + directive.Arg, forceWriteInPreviousBlock);
diff --git a/src/Libraries/NRefactory/Test/Lexer/CSharp/PreprocessingTests.cs b/src/Libraries/NRefactory/Test/Lexer/CSharp/PreprocessingTests.cs
new file mode 100644
index 0000000000..e145d73bbc
--- /dev/null
+++ b/src/Libraries/NRefactory/Test/Lexer/CSharp/PreprocessingTests.cs
@@ -0,0 +1,142 @@
+// <file>
+//     <copyright see="prj:///doc/copyright.txt"/>
+//     <license see="prj:///doc/license.txt"/>
+//     <owner name="Daniel Grunwald"/>
+//     <version>$Revision$</version>
+// </file>
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using NUnit.Framework;
+using ICSharpCode.NRefactory.Parser;
+using ICSharpCode.NRefactory.Parser.CSharp;
+using ICSharpCode.NRefactory.PrettyPrinter;
+using NUnit.Framework.SyntaxHelpers;
+
+namespace ICSharpCode.NRefactory.Tests.Lexer.CSharp
+{
+	[TestFixture]
+	public class PreprocessingTests
+	{
+		ILexer GenerateLexer(string text)
+		{
+			ILexer lexer = ParserFactory.CreateLexer(SupportedLanguage.CSharp, new StringReader(text));
+			lexer.EvaluateConditionalCompilation = true;
+			lexer.ConditionalCompilationSymbols["TEST"] = null;
+			return lexer;
+		}
+		
+		int[] GetTokenKinds(string text)
+		{
+			List<int> list = new List<int>();
+			ILexer lexer = GenerateLexer(text);
+			Token token;
+			while ((token = lexer.NextToken()) != null) {
+				list.Add(token.kind);
+				if (token.kind == Tokens.EOF)
+					break;
+			}
+			Assert.AreEqual("", lexer.Errors.ErrorOutput);
+			return list.ToArray();
+		}
+		
+		[Test]
+		public void TestEmptyIfdef()
+		{
+			Assert.AreEqual(new int[] { Tokens.Int, Tokens.EOF }, GetTokenKinds("#if true\n#endif\nint"));
+			Assert.AreEqual(new int[] { Tokens.Int, Tokens.EOF }, GetTokenKinds("#if false\n#endif\nint"));
+		}
+		
+		[Test]
+		public void TestBooleanPrimitives()
+		{
+			Assert.AreEqual(new int[] { Tokens.True, Tokens.EOF }, GetTokenKinds("#if true \n true \n #else \n false \n #endif"));
+			Assert.AreEqual(new int[] { Tokens.False, Tokens.EOF }, GetTokenKinds("#if false \n true \n #else \n false \n #endif"));
+		}
+		
+		[Test]
+		public void TestDefinedSymbols()
+		{
+			Assert.AreEqual(new int[] { Tokens.True, Tokens.EOF }, GetTokenKinds("#if TEST \n true \n #else \n false \n #endif"));
+			Assert.AreEqual(new int[] { Tokens.False, Tokens.EOF }, GetTokenKinds("#if DEBUG \n true \n #else \n false \n #endif"));
+		}
+		
+		[Test]
+		public void TestDefineUndefineSymbol()
+		{
+			Assert.AreEqual(new int[] { Tokens.False, Tokens.EOF }, GetTokenKinds("#undef TEST \n #if TEST \n true \n #else \n false \n #endif"));
+			Assert.AreEqual(new int[] { Tokens.True, Tokens.EOF }, GetTokenKinds("#define DEBUG \n #if DEBUG \n true \n #else \n false \n #endif"));
+			Assert.AreEqual(new int[] { Tokens.True, Tokens.EOF }, GetTokenKinds("#define DEBUG // comment \n #if DEBUG \n true \n #else \n false \n #endif"));
+		}
+		
+		[Test]
+		public void TestNestedIfDef()
+		{
+			string program = @"
+				#if A
+					public
+					#if B
+						abstract
+					#elif C
+						virtual
+					#endif
+					void
+				#elif B
+					protected
+					#if C // this is a comment
+						sealed
+					#endif
+					string
+				#else
+					class
+				#endif
+			";
+			Assert.AreEqual(new int[] { Tokens.Class, Tokens.EOF }, GetTokenKinds(program));
+			Assert.AreEqual(new int[] { Tokens.Public, Tokens.Void, Tokens.EOF }, GetTokenKinds("#define A\n" + program));
+			Assert.AreEqual(new int[] { Tokens.Public, Tokens.Abstract, Tokens.Void, Tokens.EOF },
+			                GetTokenKinds("#define A\n#define B\n" + program));
+			Assert.AreEqual(new int[] { Tokens.Public, Tokens.Virtual, Tokens.Void, Tokens.EOF },
+			                GetTokenKinds("#define A\n#define C\n" + program));
+			Assert.AreEqual(new int[] { Tokens.Public, Tokens.Abstract, Tokens.Void, Tokens.EOF },
+			                GetTokenKinds("#define A\n#define B\n#define C\n" + program));
+			Assert.AreEqual(new int[] { Tokens.Protected, Tokens.String, Tokens.EOF },
+			                GetTokenKinds("#define B\n" + program));
+			Assert.AreEqual(new int[] { Tokens.Protected, Tokens.Sealed, Tokens.String, Tokens.EOF },
+			                GetTokenKinds("#define B\n#define C\n" + program));
+		}
+		
+		[Test]
+		public void TestDefineInIfDef()
+		{
+			string program = @"
+				#if !A
+					#define B
+					class
+				#else
+					int
+				#endif
+				#if B
+					struct
+				#endif
+			";
+			Assert.AreEqual(new int[] { Tokens.Class, Tokens.Struct, Tokens.EOF }, GetTokenKinds(program));
+			Assert.AreEqual(new int[] { Tokens.Int, Tokens.EOF }, GetTokenKinds("#define A\n" + program));
+		}
+		
+		[Test]
+		public void TestMultilineCommentStartInIfDef()
+		{
+			string program = @"
+			#if X
+				struct
+				/*
+			#else
+				/* */ class
+			#endif 
+			";
+			Assert.AreEqual(new int[] { Tokens.Class, Tokens.EOF }, GetTokenKinds(program));
+			Assert.AreEqual(new int[] { Tokens.Struct, Tokens.Class, Tokens.EOF }, GetTokenKinds("#define X\n" + program));
+		}
+	}
+}
diff --git a/src/Libraries/NRefactory/Test/NRefactoryTests.csproj b/src/Libraries/NRefactory/Test/NRefactoryTests.csproj
index f20a322f1f..827fa32c20 100644
--- a/src/Libraries/NRefactory/Test/NRefactoryTests.csproj
+++ b/src/Libraries/NRefactory/Test/NRefactoryTests.csproj
@@ -46,6 +46,7 @@
     <Compile Include="AssemblyInfo.cs" />
     <Compile Include="Lexer\CSharp\LexerTests.cs" />
     <Compile Include="General\UnitTest.cs" />
+    <Compile Include="Lexer\CSharp\PreprocessingTests.cs" />
     <Compile Include="Lexer\VBNet\CustomLexerTests.cs" />
     <Compile Include="Parser\Expressions\LambdaExpressionTests.cs" />
     <Compile Include="Parser\Expressions\QueryExpressionTests.cs" />
diff --git a/src/Main/ICSharpCode.SharpDevelop.Dom/Project/ICSharpCode.SharpDevelop.Dom.csproj b/src/Main/ICSharpCode.SharpDevelop.Dom/Project/ICSharpCode.SharpDevelop.Dom.csproj
index a448ea8bd7..9c1fe40167 100644
--- a/src/Main/ICSharpCode.SharpDevelop.Dom/Project/ICSharpCode.SharpDevelop.Dom.csproj
+++ b/src/Main/ICSharpCode.SharpDevelop.Dom/Project/ICSharpCode.SharpDevelop.Dom.csproj
@@ -20,7 +20,7 @@
     <FileAlignment>4096</FileAlignment>
     <WarningLevel>4</WarningLevel>
     <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
-    <TargetFrameworkVersion>v2.0</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
     <RunCodeAnalysis>False</RunCodeAnalysis>
     <CodeAnalysisRules>-Microsoft.Design#CA1002;-Microsoft.Design#CA1063;-Microsoft.Performance#CA1800;-Microsoft.Security#CA2104</CodeAnalysisRules>
   </PropertyGroup>
@@ -33,7 +33,6 @@
     <CheckForOverflowUnderflow>True</CheckForOverflowUnderflow>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
-    <BaseIntermediateOutputPath>obj\</BaseIntermediateOutputPath>
     <IntermediateOutputPath>obj\Release\</IntermediateOutputPath>
     <Optimize>True</Optimize>
     <DefineConstants>TRACE</DefineConstants>
@@ -43,7 +42,9 @@
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
-    <Reference Include="System.Core" />
+    <Reference Include="System.Core">
+      <RequiredTargetFramework>3.5</RequiredTargetFramework>
+    </Reference>
     <Reference Include="System.Xml" />
     <Reference Include="Mono.Cecil">
       <HintPath>..\..\..\Libraries\Mono.Cecil\Mono.Cecil.dll</HintPath>