方法 : 式ツリービジタを実装する

[アーティクル]
09/17/2008

更新 : 2007 年 11 月

このトピックのコード例では、式ツリービジタを実装します。このクラスは、機能として式ツリーの走査、確認、またはコピーを実行する必要がある特別なクラスを作成するために継承されることを目的としています。

このクラスでは、次のトピックを参照してください。

これら 2 つのトピックには、このトピックで示される式ツリービジタ基本クラスの特別なビジタサブクラスを作成するコードが記載されています。

使用例

この式ツリービジタの実装では、最初に呼び出される Visit メソッドによって、クラスの特殊なビジタメソッドの 1 つに渡される式を式の型に基づいてディスパッチします。この特殊なビジタメソッドは、メソッドが渡された式のサブツリーを走査します。走査された後でサブ式が変更された場合 (たとえば、派生クラスのメソッドがオーバーライドされた場合)、特殊なビジタメソッドによってサブツリーの変更を含む新しい式が作成されます。それ以外の場合は、渡された式が返されます。このような再帰的な処理により、Visit に渡された元の式と同じ、またはそれを変更したバージョンの新しい式ツリーを作成できます。

Public MustInherit Class ExpressionVisitor

    Protected Sub New()
    End Sub

    Protected Overridable Function Visit(ByVal exp As Expression) As Expression
        If exp Is Nothing Then
            Return exp
        End If

        Select Case exp.NodeType
            Case ExpressionType.Negate, _
                 ExpressionType.NegateChecked, _
                 ExpressionType.Not, _
                 ExpressionType.Convert, _
                 ExpressionType.ConvertChecked, _
                 ExpressionType.ArrayLength, _
                 ExpressionType.Quote, _
                 ExpressionType.TypeAs
                Return Me.VisitUnary(CType(exp, UnaryExpression))
            Case ExpressionType.Add, _
                 ExpressionType.AddChecked, _
                 ExpressionType.Subtract, _
                 ExpressionType.SubtractChecked, _
                 ExpressionType.Multiply, _
                 ExpressionType.MultiplyChecked, _
                 ExpressionType.Divide, _
                 ExpressionType.Modulo, _
                 ExpressionType.And, _
                 ExpressionType.AndAlso, _
                 ExpressionType.Or, _
                 ExpressionType.OrElse, _
                 ExpressionType.LessThan, _
                 ExpressionType.LessThanOrEqual, _
                 ExpressionType.GreaterThan, _
                 ExpressionType.GreaterThanOrEqual, _
                 ExpressionType.Equal, _
                 ExpressionType.NotEqual, _
                 ExpressionType.Coalesce, _
                 ExpressionType.ArrayIndex, _
                 ExpressionType.RightShift, _
                 ExpressionType.LeftShift, _
                 ExpressionType.ExclusiveOr
                Return Me.VisitBinary(CType(exp, BinaryExpression))
            Case ExpressionType.TypeIs
                Return Me.VisitTypeIs(CType(exp, TypeBinaryExpression))
            Case ExpressionType.Conditional
                Return Me.VisitConditional(CType(exp, ConditionalExpression))
            Case ExpressionType.Constant
                Return Me.VisitConstant(CType(exp, ConstantExpression))
            Case ExpressionType.Parameter
                Return Me.VisitParameter(CType(exp, ParameterExpression))
            Case ExpressionType.MemberAccess
                Return Me.VisitMemberAccess(CType(exp, MemberExpression))
            Case ExpressionType.Call
                Return Me.VisitMethodCall(CType(exp, MethodCallExpression))
            Case ExpressionType.Lambda
                Return Me.VisitLambda(CType(exp, LambdaExpression))
            Case ExpressionType.New
                Return Me.VisitNew(CType(exp, NewExpression))
            Case ExpressionType.NewArrayInit, _
                 ExpressionType.NewArrayBounds
                Return Me.VisitNewArray(CType(exp, NewArrayExpression))
            Case ExpressionType.Invoke
                Return Me.VisitInvocation(CType(exp, InvocationExpression))
            Case ExpressionType.MemberInit
                Return Me.VisitMemberInit(CType(exp, MemberInitExpression))
            Case ExpressionType.ListInit
                Return Me.VisitListInit(CType(exp, ListInitExpression))
            Case Else
                Throw New Exception("Unhandled expression type: '" & exp.NodeType & "'")
        End Select
    End Function

    Protected Overridable Function VisitBinding(ByVal binding As MemberBinding) As MemberBinding
        Select Case binding.BindingType
            Case MemberBindingType.Assignment
                Return Me.VisitMemberAssignment(CType(binding, MemberAssignment))
            Case MemberBindingType.MemberBinding
                Return Me.VisitMemberMemberBinding(CType(binding, MemberMemberBinding))
            Case MemberBindingType.ListBinding
                Return Me.VisitMemberListBinding(CType(binding, MemberListBinding))
            Case Else
                Throw New Exception("Unhandled binding type '" & binding.BindingType & "'")
        End Select
    End Function

    Protected Overridable Function VisitElementInitializer(ByVal initializer As ElementInit) _
        As ElementInit

        Dim arguments = Me.VisitExpressionList(initializer.Arguments)

        If arguments IsNot initializer.Arguments Then
            Return Expression.ElementInit(initializer.AddMethod, arguments)
        End If

        Return initializer
    End Function

    Protected Overridable Function VisitUnary(ByVal u As UnaryExpression) As Expression
        Dim operand = Me.Visit(u.Operand)

        If operand IsNot u.Operand Then
            Return Expression.MakeUnary(u.NodeType, operand, u.Type, u.Method)
        End If

        Return u
    End Function

    Protected Overridable Function VisitBinary(ByVal b As BinaryExpression) As Expression
        Dim left = Me.Visit(b.Left)
        Dim right = Me.Visit(b.Right)
        Dim conversion = Me.Visit(b.Conversion)

        If left IsNot b.Left Or right IsNot b.Right Or conversion IsNot b.Conversion Then

            If b.NodeType = ExpressionType.Coalesce And b.Conversion IsNot Nothing Then
                Return Expression.Coalesce(left, right, _
                                           TryCast(conversion, LambdaExpression))
            Else
                Return Expression.MakeBinary(b.NodeType, left, right, _
                                             b.IsLiftedToNull, b.Method)
            End If
        End If

        Return b
    End Function

    Protected Overridable Function VisitTypeIs(ByVal b As TypeBinaryExpression) As Expression
        Dim expr = Me.Visit(b.Expression)

        If expr IsNot b.Expression Then
            Return Expression.TypeIs(expr, b.TypeOperand)
        End If

        Return b
    End Function

    Protected Overridable Function VisitConstant(ByVal c As ConstantExpression) As Expression
        Return c
    End Function

    Protected Overridable Function VisitConditional(ByVal c As ConditionalExpression) As Expression
        Dim test = Me.Visit(c.Test)
        Dim ifTrue = Me.Visit(c.IfTrue)
        Dim ifFalse = Me.Visit(c.IfFalse)

        If test IsNot c.Test Or ifTrue IsNot c.IfTrue Or ifFalse IsNot c.IfFalse Then
            Return Expression.Condition(test, ifTrue, ifFalse)
        End If

        Return c
    End Function

    Protected Overridable Function VisitParameter(ByVal p As ParameterExpression) As Expression
        Return p
    End Function

    Protected Overridable Function VisitMemberAccess(ByVal m As MemberExpression) As Expression
        Dim exp = Me.Visit(m.Expression)

        If exp IsNot m.Expression Then
            Return Expression.MakeMemberAccess(exp, m.Member)
        End If

        Return m
    End Function

    Protected Overridable Function VisitMethodCall(ByVal m As MethodCallExpression) As Expression
        Dim obj = Me.Visit(m.Object)
        Dim args = Me.VisitExpressionList(m.Arguments)

        If obj IsNot m.Object Or args IsNot m.Arguments Then
            Return Expression.Call(obj, m.Method, args)
        End If

        Return m
    End Function

    Protected Overridable Function VisitExpressionList( _
        ByVal original As ReadOnlyCollection(Of Expression)) As ReadOnlyCollection(Of Expression)

        Dim list As List(Of Expression) = Nothing
        Dim n = original.Count

        For i = 0 To n - 1
            Dim p = Me.Visit(original(i))

            If list IsNot Nothing Then
                list.Add(p)
            ElseIf p IsNot original(i) Then
                list = New List(Of Expression)(n)

                For j = 0 To i - 1
                    list.Add(original(j))
                Next j
                list.Add(p)
            End If
        Next i

        If list IsNot Nothing Then
            Return list.AsReadOnly()
        End If

        Return original
    End Function

    Protected Overridable Function VisitMemberAssignment(ByVal assignment As MemberAssignment) _
        As MemberAssignment

        Dim e = Me.Visit(assignment.Expression)

        If e IsNot assignment.Expression Then
            Return Expression.Bind(assignment.Member, e)
        End If

        Return assignment
    End Function

    Protected Overridable Function VisitMemberMemberBinding(ByVal binding As MemberMemberBinding) _
        As MemberMemberBinding

        Dim bindings = Me.VisitBindingList(binding.Bindings)

        If bindings IsNot binding.Bindings Then
            Return Expression.MemberBind(binding.Member, bindings)
        End If

        Return binding
    End Function

    Protected Overridable Function VisitMemberListBinding(ByVal binding As MemberListBinding) _
        As MemberListBinding

        Dim initializers = Me.VisitElementInitializerList(binding.Initializers)

        If initializers IsNot binding.Initializers Then
            Return Expression.ListBind(binding.Member, initializers)
        End If

        Return binding
    End Function

    Protected Overridable Function VisitBindingList( _
        ByVal original As ReadOnlyCollection(Of MemberBinding)) As IEnumerable(Of MemberBinding)

        Dim list As List(Of MemberBinding) = Nothing
        Dim n = original.Count

        For i = 0 To n - 1
            Dim b = Me.VisitBinding(original(i))

            If list IsNot Nothing Then
                list.Add(b)
            ElseIf b IsNot original(i) Then
                list = New List(Of MemberBinding)(n)
                For j = 0 To i - 1
                    list.Add(original(j))
                Next j
                list.Add(b)
            End If

        Next i

        If list IsNot Nothing Then
            Return list
        End If

        Return original
    End Function

    Protected Overridable Function VisitElementInitializerList( _
        ByVal original As ReadOnlyCollection(Of ElementInit)) As IEnumerable(Of ElementInit)

        Dim list As List(Of ElementInit) = Nothing
        Dim n = original.Count

        For i = 0 To n - 1
            Dim init = Me.VisitElementInitializer(original(i))
            If list IsNot Nothing Then
                list.Add(init)
            ElseIf init IsNot original(i) Then
                list = New List(Of ElementInit)(n)
                For j = 0 To i - 1
                    list.Add(original(j))
                Next j
                list.Add(init)
            End If
        Next i

        If list IsNot Nothing Then
            Return list
        End If

        Return original
    End Function

    Protected Overridable Function VisitLambda(ByVal lambda As LambdaExpression) As Expression
        Dim body = Me.Visit(lambda.Body)

        If body IsNot lambda.Body Then
            Return Expression.Lambda(lambda.Type, body, lambda.Parameters)
        End If
        Return lambda
    End Function

    Protected Overridable Function VisitNew(ByVal nex As NewExpression) As NewExpression
        Dim args = Me.VisitExpressionList(nex.Arguments)

        If args IsNot nex.Arguments Then
            If nex.Members IsNot Nothing Then
                Return Expression.[New](nex.Constructor, args, nex.Members)
            Else
                Return Expression.[New](nex.Constructor, args)
            End If
        End If

        Return nex
    End Function

    Protected Overridable Function VisitMemberInit(ByVal init As MemberInitExpression) As Expression
        Dim n = Me.VisitNew(init.NewExpression)
        Dim bindings = Me.VisitBindingList(init.Bindings)

        If n IsNot init.NewExpression Or bindings IsNot init.Bindings Then
            Return Expression.MemberInit(n, bindings)
        End If

        Return init
    End Function

    Protected Overridable Function VisitListInit(ByVal init As ListInitExpression) As Expression
        Dim n = Me.VisitNew(init.NewExpression)
        Dim initializers = Me.VisitElementInitializerList(init.Initializers)

        If n IsNot init.NewExpression Or initializers IsNot init.Initializers Then
            Return Expression.ListInit(n, initializers)
        End If

        Return init
    End Function

    Protected Overridable Function VisitNewArray(ByVal na As NewArrayExpression) As Expression
        Dim exprs = Me.VisitExpressionList(na.Expressions)
        If exprs IsNot na.Expressions Then
            If na.NodeType = ExpressionType.NewArrayInit Then
                Return Expression.NewArrayInit(na.Type.GetElementType(), exprs)
            Else
                Return Expression.NewArrayBounds(na.Type.GetElementType(), exprs)
            End If
        End If

        Return na
    End Function

    Protected Overridable Function VisitInvocation(ByVal iv As InvocationExpression) As Expression
        Dim args = Me.VisitExpressionList(iv.Arguments)
        Dim expr = Me.Visit(iv.Expression)

        If args IsNot iv.Arguments Or expr IsNot iv.Expression Then
            Return Expression.Invoke(expr, args)
        End If

        Return iv
    End Function
End Class

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<Expression> 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<Expression> args = this.VisitExpressionList(m.Arguments);
        if (obj != m.Object || args != m.Arguments)
        {
            return Expression.Call(obj, m.Method, args);
        }
        return m;
    }

    protected virtual ReadOnlyCollection<Expression> VisitExpressionList(ReadOnlyCollection<Expression> original)
    {
        List<Expression> 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<Expression>(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<MemberBinding> bindings = this.VisitBindingList(binding.Bindings);
        if (bindings != binding.Bindings)
        {
            return Expression.MemberBind(binding.Member, bindings);
        }
        return binding;
    }

    protected virtual MemberListBinding VisitMemberListBinding(MemberListBinding binding)
    {
        IEnumerable<ElementInit> initializers = this.VisitElementInitializerList(binding.Initializers);
        if (initializers != binding.Initializers)
        {
            return Expression.ListBind(binding.Member, initializers);
        }
        return binding;
    }

    protected virtual IEnumerable<MemberBinding> VisitBindingList(ReadOnlyCollection<MemberBinding> original)
    {
        List<MemberBinding> 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<MemberBinding>(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<ElementInit> VisitElementInitializerList(ReadOnlyCollection<ElementInit> original)
    {
        List<ElementInit> 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<ElementInit>(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<Expression> 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<MemberBinding> 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<ElementInit> 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<Expression> 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<Expression> 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;
    }
}

メモ :
この実装では、式ツリーの走査の開始点である Visit メソッドに、protected (Visual Basic では Protected) アクセス修飾子が含まれています。つまり、このクラスまたはその派生クラスの外部からこのメソッドにアクセスできるようにするには、Visit を呼び出す public (Visual Basic では Public) メソッドを作成する必要があります。ビジタにこの public (Visual Basic では Public) メソッドを 1 つ使用することで、呼び出し元でエントリポイントがより明確になります。

この実装では、式ツリーの走査の開始点である Visit メソッドに、protected (Visual Basic では Protected) アクセス修飾子が含まれています。つまり、このクラスまたはその派生クラスの外部からこのメソッドにアクセスできるようにするには、Visit を呼び出す public (Visual Basic では Public) メソッドを作成する必要があります。ビジタにこの public (Visual Basic では Public) メソッドを 1 つ使用することで、呼び出し元でエントリポイントがより明確になります。

コードのコンパイル方法

プロジェクトで System.Core.dll がまだ参照されていない場合は、System.Core.dll への参照を追加します。
using ディレクティブ (Visual Basic では Imports ステートメント) を名前空間 System.Collections.Generic、System.Collections.ObjectModel、および System.Linq.Expressions に追加します。

参照

処理手順

方法 : 式ツリーを変更する

チュートリアル : IQueryable LINQ プロバイダの作成

概念

式ツリー

方法 : 式ツリー ビジタを実装する

使用例

コードのコンパイル方法

参照

処理手順

概念

その他のリソース

方法 : 式ツリービジタを実装する