Class CooperativeExpressionVisitor

Cooperative expression visitor that dispatches expression tree node visits to other visitors based on metadata attributes applied to reflection objects.

Inheritance
System.Object
CooperativeExpressionVisitor
Namespace: System.Linq.CompilerServices
Assembly: Nuqleon.Linq.CompilerServices.dll
Syntax
public class CooperativeExpressionVisitor : ExpressionVisitor
Examples

Consider the following method definition:

[Visitor(typeof(MyVisitor))]
static int Foo(int x)
{
    throw new NotImplementedException();
}

In here, the Foo method is annotated with the VisitorAttribute, specifying the type of the visitor that will process nodes using this method, e.g. in a MethodCallExpression. This type implements IExpressionVisitor:

class MyVisitor : IRecursiveExpressionVisitor
{
    public bool TryVisit(Expression expression, Func<Expression, Expression> visit, out Expression result)
    {
        // No-op rewrite for illustration purposes
        var call = (MethodCallExpression)expression;
        var arg = visit(call.Arguments[0]);
        result = call.Update(null, new[] { arg });
        return true;
    }
}

Using the CooperativeExpressionVisitor, we can visit a tree that calls Foo:

var f = (Expression<Func<int, int>>)(x => Foo(x + 1));
var g = new CooperativeExpressionVisitor().Visit(f);

Constructors

CooperativeExpressionVisitor()

Declaration
public CooperativeExpressionVisitor()

Methods

VisitBinary(BinaryExpression)

Visits a BinaryExpression. If the binary expression is using operator overloading, the MethodInfo of the operator implementation is considered for cooperative rewriting.

Declaration
protected override Expression VisitBinary(BinaryExpression node)
Parameters
Type Name Description
System.Linq.Expressions.BinaryExpression node

The expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The modified expression, if it or any subexpression was modified; otherwise, returns the original expression.

VisitIndex(IndexExpression)

Visits an IndexExpression. The PropertyInfo of the indexing operation is considered for cooperative rewriting.

Declaration
protected override Expression VisitIndex(IndexExpression node)
Parameters
Type Name Description
System.Linq.Expressions.IndexExpression node

The expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The modified expression, if it or any subexpression was modified; otherwise, returns the original expression.

VisitMember(MemberExpression)

Visits a MemberExpression. The MemberInfo of the member lookup is considered for cooperative rewriting.

Declaration
protected override Expression VisitMember(MemberExpression node)
Parameters
Type Name Description
System.Linq.Expressions.MemberExpression node

The expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The modified expression, if it or any subexpression was modified; otherwise, returns the original expression.

VisitMethodCall(MethodCallExpression)

Visits a MethodCallExpression. The MethodInfo of the method call is considered for cooperative rewriting.

Declaration
protected override Expression VisitMethodCall(MethodCallExpression node)
Parameters
Type Name Description
System.Linq.Expressions.MethodCallExpression node

The expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The modified expression, if it or any subexpression was modified; otherwise, returns the original expression.

VisitNew(NewExpression)

Visits a NewExpression. The ConstructorInfo of the constructor call is considered for cooperative rewriting.

Declaration
protected override Expression VisitNew(NewExpression node)
Parameters
Type Name Description
System.Linq.Expressions.NewExpression node

The expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The modified expression, if it or any subexpression was modified; otherwise, returns the original expression.

VisitUnary(UnaryExpression)

Visits a UnaryExpression. If the unary expression is using operator overloading, the MethodInfo of the operator implementation is considered for cooperative rewriting.

Declaration
protected override Expression VisitUnary(UnaryExpression node)
Parameters
Type Name Description
System.Linq.Expressions.UnaryExpression node

The expression to visit.
Returns
Type Description
System.Linq.Expressions.Expression

The modified expression, if it or any subexpression was modified; otherwise, returns the original expression.