54 lines
2.6 KiB
C#
54 lines
2.6 KiB
C#
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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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using System.Text;
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namespace PoweredSoft.DynamicLinq.Helpers
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{
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public static class QueryablePathHelpers
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{
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public delegate Expression SimplePathNavigated(Expression before, MemberExpression member, bool isFirst, bool isLast);
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public delegate Expression CollectionPathNavigated(Expression before, MemberExpression member, bool isFirst, bool isLast);
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public delegate Expression CollectionHandling(Expression parent, Expression innerExpression, LambdaExpression innerExpressionLambda);
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internal static Expression InternalNavigatePath(Expression before, List<string> parts, SimplePathNavigated simple, CollectionPathNavigated collection, CollectionHandling collectionHandling)
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{
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var isFirst = before is ParameterExpression;
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var isLast = parts.Count() == 1;
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var currentExpression = Expression.PropertyOrField(before, parts.First());
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var isEnumerable = QueryableHelpers.IsGenericEnumerable(currentExpression);
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// allow interaction through callback.
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var alteredExpression = isEnumerable ? simple(before, currentExpression, isFirst, isLast) : collection(before, currentExpression, isFirst, isLast);
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// if its last we are done :)
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if (isLast)
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return alteredExpression;
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// not enumerable pretty simple.
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if (!isEnumerable)
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return InternalNavigatePath(alteredExpression, parts.Skip(1).ToList(), simple, collection, collectionHandling);
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// enumerable.
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var listGenericArgumentType = alteredExpression.Type.GetGenericArguments().First();
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// sub param.
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var innerParameter = Expression.Parameter(listGenericArgumentType);
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var innerExpr = InternalNavigatePath(innerParameter, parts.Skip(1).ToList(), simple, collection, collectionHandling);
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var lambda = Expression.Lambda(innerExpr, innerParameter);
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var collectionHandlingResult = collectionHandling(alteredExpression, innerExpr, lambda);
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return collectionHandlingResult;
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}
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public static Expression NavigatePath(ParameterExpression param, string path,
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SimplePathNavigated simple,
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CollectionPathNavigated collection,
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CollectionHandling collectionHandling)
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{
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var parts = path.Split('.').ToList();
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return InternalNavigatePath(param, parts, simple, collection, collectionHandling);
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}
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}
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}
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