snugs
0d48732546
Send isLiveMode directly into data readers instead of resolving from data feed endpoint Added some expression extensions, AsEnumerable() :) Fixed Identity names, added optional name parameter for deconflicting
89 lines
4.0 KiB
C#
89 lines
4.0 KiB
C#
/*
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* QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
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* Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Linq.Expressions;
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namespace QuantConnect.Util
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{
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/// <summary>
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/// Provides methods for constructing expressions at runtime
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/// </summary>
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public static class ExpressionBuilder
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{
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/// <summary>
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/// Constructs a selector of the form: x => x.propertyOrField where x is an instance of 'type'
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/// </summary>
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/// <param name="type">The type of the parameter in the expression</param>
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/// <param name="propertyOrField">The name of the property or field to bind to</param>
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/// <returns>A new lambda expression that represents accessing the property or field on 'type'</returns>
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public static LambdaExpression MakePropertyOrFieldSelector(Type type, string propertyOrField)
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{
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var parameter = Expression.Parameter(type);
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var property = Expression.PropertyOrField(parameter, propertyOrField);
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var lambda = Expression.Lambda(property, parameter);
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return lambda;
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}
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/// <summary>
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/// Constructs a selector of the form: x => x.propertyOrField where x is an instance of 'type'
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/// </summary>
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/// <typeparam name="T">The type of the parameter in the expression</typeparam>
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/// <typeparam name="TProperty">The type of the property or field being accessed in the expression</typeparam>
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/// <param name="propertyOrField">The name of the property or field to bind to</param>
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/// <returns>A new lambda expression that represents accessing the property or field on 'type'</returns>
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public static Expression<Func<T, TProperty>> MakePropertyOrFieldSelector<T, TProperty>(string propertyOrField)
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{
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return (Expression<Func<T, TProperty>>) MakePropertyOrFieldSelector(typeof (T), propertyOrField);
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}
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/// <summary>
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/// Converts the specified expression into an enumerable of expressions by walking the expression tree
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/// </summary>
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/// <param name="expression">The expression to enumerate</param>
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/// <returns>An enumerable containing all expressions in the input expression</returns>
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public static IEnumerable<Expression> AsEnumerable(this Expression expression)
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{
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var walker = new ExpressionWalker();
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walker.Visit(expression);
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return walker.Expressions;
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}
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/// <summary>
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/// Returns all the expressions of the specified type in the given expression tree
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/// </summary>
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/// <typeparam name="T">The type of expression to search for</typeparam>
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/// <param name="expression">The expression to search</param>
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/// <returns>All expressions of the given type in the specified expression</returns>
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public static IEnumerable<T> OfType<T>(this Expression expression)
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where T : Expression
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{
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return expression.AsEnumerable().OfType<T>();
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}
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private class ExpressionWalker : ExpressionVisitor
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{
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public readonly HashSet<Expression> Expressions = new HashSet<Expression>();
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public override Expression Visit(Expression node)
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{
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Expressions.Add(node);
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return base.Visit(node);
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}
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}
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}
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}
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