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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Signum.Utilities.ExpressionTrees;
using System.Linq.Expressions;
using System.Reflection;
using Signum.Utilities.Reflection;
namespace Signum.Engine.Linq
{
/// <summary>
/// Evaluates & replaces sub-trees when first candidate is reached (top-down)
/// </summary>
public class MetaEvaluator : SimpleExpressionVisitor
{
public static Expression Clean(Expression expression)
{
Expression expand = ExpressionCleaner.Clean(expression, MetaEvaluator.PartialEval, false);
Expression simplified = OverloadingSimplifier.Simplify(expand);
return simplified;
}
HashSet<Expression> candidates;
private MetaEvaluator() { }
/// <summary>
/// Performs evaluation & replacement of independent sub-trees
/// </summary>
/// <param name="expression">The root of the expression tree.</param>
/// <param name="fnCanBeEvaluated">A function that decides whether a given expression node can be part of the local function.</param>
/// <returns>A new tree with sub-trees evaluated and replaced.</returns>
public static Expression PartialEval(Expression exp)
{
return new MetaEvaluator { candidates = ExpressionNominator.Nominate(exp) }.Visit(exp);
}
protected override Expression Visit(Expression exp)
{
if (exp == null)
{
return null;
}
if (this.candidates.Contains(exp) && exp.NodeType != ExpressionType.Constant)
{
if (exp.Type.IsAssignableFrom(typeof(IQueryable<>)))
return ExpressionEvaluator.PartialEval(exp);
return miConstant.GetInvoker(exp.Type)();
}
return base.Visit(exp);
}
static GenericInvoker<Func<ConstantExpression>> miConstant = new GenericInvoker<Func<ConstantExpression>>(() => Constant<int>());
static ConstantExpression Constant<T>()
{
return Expression.Constant(default(T), typeof(T));
}
}
}
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I'm Computer Scientist, one of the founders of Signum Software, and the lead developer behind Signum Framework.
www.signumframework.com
I love programming in C#, Linq, Compilers, Algorithms, Functional Programming, Computer Graphics, Maths...