C# Expression visitor
////// Expression visitor /// (from http://blogs.msdn.com/mattwar/archive/2007/07/31/linq-building-an-iqueryable-provider-part-ii.aspx) /// public abstract class ExpressionVisitor { protected ExpressionVisitor() { } protected virtual Expression Visit(Expression exp) { if (exp == null) return exp; switch (exp.NodeType) { case ExpressionType.Negate: case ExpressionType.NegateChecked: case ExpressionType.Not: case ExpressionType.Convert: case ExpressionType.ConvertChecked: case ExpressionType.ArrayLength: case ExpressionType.Quote: case ExpressionType.TypeAs: return this.VisitUnary((UnaryExpression)exp); case ExpressionType.Add: case ExpressionType.AddChecked: case ExpressionType.Subtract: case ExpressionType.SubtractChecked: case ExpressionType.Multiply: case ExpressionType.MultiplyChecked: case ExpressionType.Divide: case ExpressionType.Modulo: case ExpressionType.And: case ExpressionType.AndAlso: case ExpressionType.Or: case ExpressionType.OrElse: case ExpressionType.LessThan: case ExpressionType.LessThanOrEqual: case ExpressionType.GreaterThan: case ExpressionType.GreaterThanOrEqual: case ExpressionType.Equal: case ExpressionType.NotEqual: case ExpressionType.Coalesce: case ExpressionType.ArrayIndex: case ExpressionType.RightShift: case ExpressionType.LeftShift: case ExpressionType.ExclusiveOr: return this.VisitBinary((BinaryExpression)exp); case ExpressionType.TypeIs: return this.VisitTypeIs((TypeBinaryExpression)exp); case ExpressionType.Conditional: return this.VisitConditional((ConditionalExpression)exp); case ExpressionType.Constant: return this.VisitConstant((ConstantExpression)exp); case ExpressionType.Parameter: return this.VisitParameter((ParameterExpression)exp); case ExpressionType.MemberAccess: return this.VisitMemberAccess((MemberExpression)exp); case ExpressionType.Call: return this.VisitMethodCall((MethodCallExpression)exp); case ExpressionType.Lambda: return this.VisitLambda((LambdaExpression)exp); case ExpressionType.New: return this.VisitNew((NewExpression)exp); case ExpressionType.NewArrayInit: case ExpressionType.NewArrayBounds: return this.VisitNewArray((NewArrayExpression)exp); case ExpressionType.Invoke: return this.VisitInvocation((InvocationExpression)exp); case ExpressionType.MemberInit: return this.VisitMemberInit((MemberInitExpression)exp); case ExpressionType.ListInit: return this.VisitListInit((ListInitExpression)exp); default: throw new Exception(string.Format("Unhandled expression type: '{0}'", exp.NodeType)); } } protected virtual MemberBinding VisitBinding(MemberBinding binding) { switch (binding.BindingType) { case MemberBindingType.Assignment: return this.VisitMemberAssignment((MemberAssignment)binding); case MemberBindingType.MemberBinding: return this.VisitMemberMemberBinding((MemberMemberBinding)binding); case MemberBindingType.ListBinding: return this.VisitMemberListBinding((MemberListBinding)binding); default: throw new Exception(string.Format("Unhandled binding type '{0}'", binding.BindingType)); } } protected virtual ElementInit VisitElementInitializer(ElementInit initializer) { ReadOnlyCollection arguments = this.VisitExpressionList(initializer.Arguments); if (arguments != initializer.Arguments) { return Expression.ElementInit(initializer.AddMethod, arguments); } return initializer; } protected virtual Expression VisitUnary(UnaryExpression u) { Expression operand = this.Visit(u.Operand); if (operand != u.Operand) { return Expression.MakeUnary(u.NodeType, operand, u.Type, u.Method); } return u; } protected virtual Expression VisitBinary(BinaryExpression b) { Expression left = this.Visit(b.Left); Expression right = this.Visit(b.Right); Expression conversion = this.Visit(b.Conversion); if (left != b.Left || right != b.Right || conversion != b.Conversion) { if (b.NodeType == ExpressionType.Coalesce && b.Conversion != null) return Expression.Coalesce(left, right, conversion as LambdaExpression); else return Expression.MakeBinary(b.NodeType, left, right, b.IsLiftedToNull, b.Method); } return b; } protected virtual Expression VisitTypeIs(TypeBinaryExpression b) { Expression expr = this.Visit(b.Expression); if (expr != b.Expression) { return Expression.TypeIs(expr, b.TypeOperand); } return b; } protected virtual Expression VisitConstant(ConstantExpression c) { return c; } protected virtual Expression VisitConditional(ConditionalExpression c) { Expression test = this.Visit(c.Test); Expression ifTrue = this.Visit(c.IfTrue); Expression ifFalse = this.Visit(c.IfFalse); if (test != c.Test || ifTrue != c.IfTrue || ifFalse != c.IfFalse) { return Expression.Condition(test, ifTrue, ifFalse); } return c; } protected virtual Expression VisitParameter(ParameterExpression p) { return p; } protected virtual Expression VisitMemberAccess(MemberExpression m) { Expression exp = this.Visit(m.Expression); if (exp != m.Expression) { return Expression.MakeMemberAccess(exp, m.Member); } return m; } protected virtual Expression VisitMethodCall(MethodCallExpression m) { Expression obj = this.Visit(m.Object); IEnumerable args = this.VisitExpressionList(m.Arguments); if (obj != m.Object || args != m.Arguments) { return Expression.Call(obj, m.Method, args); } return m; } protected virtual ReadOnlyCollection VisitExpressionList(ReadOnlyCollection original) { List list = null; for (int i = 0, n = original.Count; i < n; i++) { Expression p = this.Visit(original[i]); if (list != null) { list.Add(p); } else if (p != original[i]) { list = new List (n); for (int j = 0; j < i; j++) { list.Add(original[j]); } list.Add(p); } } if (list != null) { return list.AsReadOnly(); } return original; } protected virtual MemberAssignment VisitMemberAssignment(MemberAssignment assignment) { Expression e = this.Visit(assignment.Expression); if (e != assignment.Expression) { return Expression.Bind(assignment.Member, e); } return assignment; } protected virtual MemberMemberBinding VisitMemberMemberBinding(MemberMemberBinding binding) { IEnumerable bindings = this.VisitBindingList(binding.Bindings); if (bindings != binding.Bindings) { return Expression.MemberBind(binding.Member, bindings); } return binding; } protected virtual MemberListBinding VisitMemberListBinding(MemberListBinding binding) { IEnumerable initializers = this.VisitElementInitializerList(binding.Initializers); if (initializers != binding.Initializers) { return Expression.ListBind(binding.Member, initializers); } return binding; } protected virtual IEnumerable VisitBindingList(ReadOnlyCollection original) { List list = null; for (int i = 0, n = original.Count; i < n; i++) { MemberBinding b = this.VisitBinding(original[i]); if (list != null) { list.Add(b); } else if (b != original[i]) { list = new List (n); for (int j = 0; j < i; j++) { list.Add(original[j]); } list.Add(b); } } if (list != null) return list; return original; } protected virtual IEnumerable VisitElementInitializerList(ReadOnlyCollection original) { List list = null; for (int i = 0, n = original.Count; i < n; i++) { ElementInit init = this.VisitElementInitializer(original[i]); if (list != null) { list.Add(init); } else if (init != original[i]) { list = new List (n); for (int j = 0; j < i; j++) { list.Add(original[j]); } list.Add(init); } } if (list != null) return list; return original; } protected virtual Expression VisitLambda(LambdaExpression lambda) { Expression body = this.Visit(lambda.Body); if (body != lambda.Body) { return Expression.Lambda(lambda.Type, body, lambda.Parameters); } return lambda; } protected virtual NewExpression VisitNew(NewExpression nex) { IEnumerable args = this.VisitExpressionList(nex.Arguments); if (args != nex.Arguments) { if (nex.Members != null) return Expression.New(nex.Constructor, args, nex.Members); else return Expression.New(nex.Constructor, args); } return nex; } protected virtual Expression VisitMemberInit(MemberInitExpression init) { NewExpression n = this.VisitNew(init.NewExpression); IEnumerable bindings = this.VisitBindingList(init.Bindings); if (n != init.NewExpression || bindings != init.Bindings) { return Expression.MemberInit(n, bindings); } return init; } protected virtual Expression VisitListInit(ListInitExpression init) { NewExpression n = this.VisitNew(init.NewExpression); IEnumerable initializers = this.VisitElementInitializerList(init.Initializers); if (n != init.NewExpression || initializers != init.Initializers) { return Expression.ListInit(n, initializers); } return init; } protected virtual Expression VisitNewArray(NewArrayExpression na) { IEnumerable exprs = this.VisitExpressionList(na.Expressions); if (exprs != na.Expressions) { if (na.NodeType == ExpressionType.NewArrayInit) { return Expression.NewArrayInit(na.Type.GetElementType(), exprs); } else { return Expression.NewArrayBounds(na.Type.GetElementType(), exprs); } } return na; } protected virtual Expression VisitInvocation(InvocationExpression iv) { IEnumerable args = this.VisitExpressionList(iv.Arguments); Expression expr = this.Visit(iv.Expression); if (args != iv.Arguments || expr != iv.Expression) { return Expression.Invoke(expr, args); } return iv; } }
posted on 2013-05-17 13:57 RockyLOMO 阅读(...) 评论(...) 编辑 收藏