C# IfStatementSyntax类代码示例

        static bool HasConflictingNames(SyntaxNodeAnalysisContext nodeContext, IfStatementSyntax ifElseStatement)
        {
            var block = ifElseStatement.Else.Statement as BlockSyntax;
            if (block == null || block.Statements.Count == 0)
                return false;

            var member = ifElseStatement.Ancestors().FirstOrDefault(a => a is MemberDeclarationSyntax);

            var priorLocalDeclarations = new List<string>();
            foreach (var localDecl in member.DescendantNodes().Where(n => n.SpanStart < ifElseStatement.Else.SpanStart).OfType<LocalDeclarationStatementSyntax>()) {
                foreach (var v in localDecl.Declaration.Variables)
                    priorLocalDeclarations.Add(v.Identifier.ValueText);
            }

            foreach (var sym in block.Statements)
            {
                var decl = sym as LocalDeclarationStatementSyntax;
                if (decl == null)
                    continue;
                
                if (priorLocalDeclarations.Contains(s => decl.Declaration.Variables.Any(v => v.Identifier.ValueText == s)))
                    return true;
            }
            return false;
        }

        protected override SyntaxNode VisitIfStatement(IfStatementSyntax node)
        {
            if (!node.DescendentNodes().OfType<BlockSyntax>().Any())
            {
                node = node.Update (node.IfKeyword, node.OpenParenToken, node.Condition, node.CloseParenToken,
                                    Syntax.Block (statements: node.Statement), node.ElseOpt);
            }

            if (node.ElseOpt != null)
            {
                ElseClauseSyntax elseOpt = node.ElseOpt;
                IfStatementSyntax ifSyntax = elseOpt.Statement as IfStatementSyntax;
                if (ifSyntax != null)
                {
                    if (!ifSyntax.DescendentNodes().OfType<BlockSyntax>().Any())
                    {
                        ifSyntax = ifSyntax.Update (ifSyntax.IfKeyword, ifSyntax.OpenParenToken, ifSyntax.Condition, ifSyntax.CloseParenToken,
                                                    Syntax.Block (statements: ifSyntax.Statement), ifSyntax.ElseOpt);

                        elseOpt = elseOpt.Update (elseOpt.ElseKeyword, ifSyntax);
                    }
                }
                else if (!elseOpt.DescendentNodes().OfType<BlockSyntax>().Any())
                    elseOpt = node.ElseOpt.Update (node.ElseOpt.ElseKeyword, Syntax.Block (statements: node.ElseOpt.Statement));

                if (elseOpt != node.ElseOpt)
                    node = node.Update (node.IfKeyword, node.OpenParenToken, node.Condition, node.CloseParenToken, node.Statement, elseOpt);
            }

            return base.VisitIfStatement (node);
        }

        static bool GetMatch(IfStatementSyntax node, out ExpressionSyntax c, out ReturnStatementSyntax e1, out ReturnStatementSyntax e2, out ReturnStatementSyntax rs)
        {
            rs = e1 = e2 = null;
            c = node.Condition;
            //attempt to match if(condition) return else return
            e1 = ConvertIfStatementToNullCoalescingExpressionAction.GetSimpleStatement(node.Statement) as ReturnStatementSyntax;
            if (e1 == null)
                return false;
            e2 = node.Else != null ? ConvertIfStatementToNullCoalescingExpressionAction.GetSimpleStatement(node.Else.Statement) as ReturnStatementSyntax : null;
            //match
            if (e1 != null && e2 != null)
            {
                return true;
            }

            //attempt to match if(condition) return
            if (e1 != null)
            {
                rs = node.Parent.ChildThatContainsPosition(node.GetTrailingTrivia().Max(t => t.FullSpan.End) + 1).AsNode() as ReturnStatementSyntax;
                if (rs != null)
                {
                    e2 = rs;
                    return true;
                }
            }
            return false;
        }

        private static SyntaxNode CalculateNewRoot(SyntaxNode root, IfStatementSyntax ifStatement)
        {
            SyntaxNode newRoot;
            var isTrue = ifStatement.Condition.IsKind(SyntaxKind.TrueLiteralExpression);

            if (isTrue)
            {
                var block = ifStatement.Statement as BlockSyntax;
                newRoot = block == null
                    ? root.ReplaceNode(ifStatement, ifStatement.Statement)
                    : root.ReplaceNode(ifStatement, block.Statements);
            }
            else
            {
                if (ifStatement.Else == null)
                {
                    newRoot = root.RemoveNode(ifStatement, SyntaxRemoveOptions.KeepNoTrivia);
                }
                else
                {
                    var block = ifStatement.Else.Statement as BlockSyntax;
                    newRoot = block == null
                        ? root.ReplaceNode(ifStatement, ifStatement.Else.Statement)
                        : root.ReplaceNode(ifStatement, block.Statements);
                }
            }

            return newRoot.WithAdditionalAnnotations(Formatter.Annotation);
        }

        static bool GetMatch(IfStatementSyntax node, out ExpressionSyntax c, out ReturnStatementSyntax e1, out ReturnStatementSyntax e2, out ReturnStatementSyntax rs)
        {
            rs = e1 = e2 = null;
            c = node.Condition;
            //attempt to match if(condition) return else return
            e1 = ConvertIfStatementToNullCoalescingExpressionAction.GetSimpleStatement(node.Statement) as ReturnStatementSyntax;
            if (e1 == null)
                return false;
            e2 = node.Else != null ? ConvertIfStatementToNullCoalescingExpressionAction.GetSimpleStatement(node.Else.Statement) as ReturnStatementSyntax : null;
            //match
            if (e1 != null && e2 != null)
            {
                return true;
            }

            //attempt to match if(condition) return; return
            if (e1 != null)
            {
                var parentBlock = node.Parent as BlockSyntax;
                if (parentBlock == null)
                    return false;
                var index = parentBlock.Statements.IndexOf(node);
                if (index + 1 < parentBlock.Statements.Count)
                {
                    rs = parentBlock.Statements[index + 1] as ReturnStatementSyntax;
                }

                if (rs != null)
                {
                    e2 = rs;
                    return true;
                }
            }
            return false;
        }

        public static IEnumerable<StatementSyntax> LopsidedTerminalBranchesToGuardedBranches(IfStatementSyntax syntax)
        {
            Contract.Requires(syntax != null);
            Contract.Requires(syntax.Parent is BlockSyntax);

            if (syntax.Statement.IsGuaranteedToJumpOut()) return new[] { syntax };
            if (syntax.Else != null && syntax.Else.Statement.IsGuaranteedToJumpOut()) return new[] { syntax };
            var allowedJump = syntax.TryGetEquivalentJumpAfterStatement();
            if (allowedJump == null) return new[] { syntax };

            var trueBloat = syntax.Statement.Bloat();
            var falseBloat = syntax.Else == null ? 0 : syntax.Else.Statement.Bloat();
            if (trueBloat < falseBloat * 2 - 10) {
                // inline the false branch, guard with the true branch
                return syntax.Else.Statement.Statements().Prepend(
                    syntax.WithStatement(syntax.Statement.BracedTo(syntax.Statement.Statements().Concat(new[] {allowedJump})))
                          .WithElse(null));
            }
            if (falseBloat < trueBloat * 2 - 10) {
                // inline the true branch, guard with the false branch
                return syntax.Statement.Statements().Prepend(
                    syntax.WithCondition(syntax.Condition.Inverted())
                          .WithStatement(syntax.Else == null ? allowedJump : syntax.Else.Statement.BracedTo(syntax.Else.Statement.Statements().Concat(new[] {allowedJump})))
                          .WithElse(null));
            }

            return new[] { syntax };
        }

        private async Task<Document> FixSpacingAsync(Document document, IfStatementSyntax ifStatement, CancellationToken c)
        {
            // This method will generate a new if-statement node with a single space between the if-keyword and the opening parenthesis.
            var generator = SyntaxGenerator.GetGenerator(document);
        
            // The new if-statement will need to retain the same statements as the old if-statement.
            var ifBlock = ifStatement.Statement as BlockSyntax;
            var ifBlockStatements = ifBlock.Statements;

            // The new if-statement should retain the formatting of the trivia before and after the if-statement.
            // The following statements extract the original trivia.
            var ifKeyword = ifStatement.IfKeyword;
            var leadingTrivia = ifKeyword.LeadingTrivia;
            var closeBrace = ifBlock.CloseBraceToken;
            var trailingTrivia = closeBrace.TrailingTrivia;

            // If-statements generated using SyntaxGenerator are formatted with the desired spacing by default so this is not specified explicitly.
            var newIfStatement = generator.IfStatement(ifStatement.Condition, ifBlockStatements).WithLeadingTrivia(leadingTrivia).WithTrailingTrivia(trailingTrivia);

            // This statement gets the top of the syntax tree so that the old if-statement node can be replaced with the new one.
            var root = await document.GetSyntaxRootAsync();

            // A new root is created with the old if-statement replaced by the new one.
            var newRoot = root.ReplaceNode(ifStatement, newIfStatement);

            // A new document with the new root is returned.
            var newDocument = document.WithSyntaxRoot(newRoot);
            return newDocument;
    }

 public BoundIfStatement(IfStatementSyntax syntax, BoundExpression condition, BoundStatement consequence, BoundStatement alternativeOpt)
     : base(BoundNodeKind.IfStatement, syntax)
 {
     Condition = condition;
     Consequence = consequence;
     AlternativeOpt = alternativeOpt;
 }

        public static IfStatementSyntax AddBraces(IfStatementSyntax ifStatement)
        {
            Debug.Assert(ifStatement != null && NeedsBraces(ifStatement));

            return ifStatement
                .WithStatement(SyntaxFactory.Block(ifStatement.Statement))
                .WithAdditionalAnnotations(Formatter.Annotation);
        }

        private void HandleIf(SyntaxNodeAnalysisContext context, IfStatementSyntax ifStatement)
        {
            if (ifStatement.Statement is BlockSyntax)
            {
                return;
            }

            context.ReportDiagnostic(Diagnostic.Create(Rule, ifStatement.IfKeyword.GetLocation()));
        }

        private Document ConvertToConditional(Document document, SemanticModel semanticModel, IfStatementSyntax ifStatement, StatementSyntax replacementStatement, CancellationToken cancellationToken)
        {
            var oldRoot = semanticModel.SyntaxTree.GetRoot();
            var newRoot = oldRoot.ReplaceNode(
                oldNode: ifStatement,
                newNode: replacementStatement.WithAdditionalAnnotations(Formatter.Annotation));

            return document.WithSyntaxRoot(newRoot);
        }

 public BoundIfStatement(
     BoundExpression boundExpression,
     BoundScopeStatement boundStatements,
     IfStatementSyntax statementSyntax)
     : base(statementSyntax)
 {
     BoundExpression = boundExpression;
     BoundStatements = boundStatements;
 }

 private async Task<Document> AddBracesAsync(Document document, IfStatementSyntax ifStatement, CancellationToken cancellationToken)
 {
     var nonBlockedStatement = ifStatement.Statement as ExpressionStatementSyntax;
     var newBlockedStatement = SyntaxFactory.Block(statements: nonBlockedStatement).WithAdditionalAnnotations(annotations: Formatter.Annotation);
     var newIfStatement = ifStatement.ReplaceNode(oldNode: nonBlockedStatement, newNode: newBlockedStatement);
     var root = await document.GetSyntaxRootAsync();
     var newRoot = root.ReplaceNode(oldNode: ifStatement, newNode: newIfStatement);
     var newDocument = document.WithSyntaxRoot(newRoot);
     return newDocument;
 }

 public static string IfStatement(IfStatementSyntax statement)
 {
     var output = statement.IfKeyword.Text + " (";
     output += SyntaxNode(statement.Condition);
     output += ")" + NewLine + SyntaxNode(statement.Statement);
     if (statement.Else != null)
     {
         output += SyntaxNode(statement.Else);
     }
     return output;
 }

        internal static bool ParseIfStatement(IfStatementSyntax node, out ExpressionSyntax condition, out ExpressionSyntax target, out AssignmentExpressionSyntax whenTrue, out AssignmentExpressionSyntax whenFalse)
        {
            condition = null;
            target = null;
            whenTrue = null;
            whenFalse = null;

            if (node == null || node.Else == null || node.Parent is IfStatementSyntax || node.Else.Statement is IfStatementSyntax)
                return false;

            condition = node.Condition;
            //make sure to check for multiple statements
            ExpressionStatementSyntax whenTrueExprStatement, whenFalseExprStatement;
            var embeddedBlock = node.Statement as BlockSyntax;
            if (embeddedBlock != null)
            {
                if (embeddedBlock.Statements.Count > 1)
                    return false;
                var childNodes = embeddedBlock.ChildNodes();
                if (childNodes.Count() > 1)
                    return false;
                whenTrueExprStatement = childNodes.OfType<ExpressionStatementSyntax>().FirstOrDefault();
            }
            else
            {
                whenTrueExprStatement = node.Statement as ExpressionStatementSyntax;
            }

            var elseBlock = node.Else.Statement as BlockSyntax;
            if (elseBlock != null)
            {
                if (elseBlock.Statements.Count > 1)
                    return false;
                var childNodes = elseBlock.ChildNodes();
                if (childNodes.Count() > 1)
                    return false;
                whenFalseExprStatement = childNodes.OfType<ExpressionStatementSyntax>().FirstOrDefault();
            }
            else
            {
                whenFalseExprStatement = node.Else.Statement as ExpressionStatementSyntax;
            }

            if (whenTrueExprStatement == null || whenFalseExprStatement == null)
                return false;

            whenTrue = whenTrueExprStatement.Expression as AssignmentExpressionSyntax;
            whenFalse = whenFalseExprStatement.Expression as AssignmentExpressionSyntax;
            if (whenTrue == null || whenFalse == null || whenTrue.Kind() != whenFalse.Kind() ||
                !SyntaxFactory.AreEquivalent(whenTrue.Left, whenFalse.Left))
                return false;

            return true;
        }