72 lines
2.8 KiB
C#
72 lines
2.8 KiB
C#
using System.Collections.Generic;
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using System.Diagnostics.CodeAnalysis;
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using System.Linq.Expressions;
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using System.Linq;
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using System;
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namespace Oqtane.Extensions
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{
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public static class QueryableExtensions
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{
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public static IQueryable<T> FilterByItems<T, TItem>(this IQueryable<T> query, IEnumerable<TItem> items,
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Expression<Func<T, TItem, bool>> filterPattern, bool isOr)
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{
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Expression predicate = null;
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foreach (var item in items)
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{
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var itemExpr = Expression.Constant(item);
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var itemCondition = ExpressionReplacer.Replace(filterPattern.Body, filterPattern.Parameters[1], itemExpr);
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if (predicate == null)
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predicate = itemCondition;
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else
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{
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predicate = Expression.MakeBinary(isOr ? ExpressionType.OrElse : ExpressionType.AndAlso, predicate,
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itemCondition);
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}
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}
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predicate ??= Expression.Constant(false);
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var filterLambda = Expression.Lambda<Func<T, bool>>(predicate, filterPattern.Parameters[0]);
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return query.Where(filterLambda);
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}
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class ExpressionReplacer : ExpressionVisitor
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{
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readonly IDictionary<Expression, Expression> _replaceMap;
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public ExpressionReplacer(IDictionary<Expression, Expression> replaceMap)
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{
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_replaceMap = replaceMap ?? throw new ArgumentNullException(nameof(replaceMap));
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}
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[return: NotNullIfNotNull(nameof(node))]
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public override Expression Visit(Expression node)
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{
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if (node != null && _replaceMap.TryGetValue(node, out var replacement))
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return replacement;
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return base.Visit(node);
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}
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public static Expression Replace(Expression expr, Expression toReplace, Expression toExpr)
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{
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return new ExpressionReplacer(new Dictionary<Expression, Expression> { { toReplace, toExpr } }).Visit(expr);
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}
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public static Expression Replace(Expression expr, IDictionary<Expression, Expression> replaceMap)
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{
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return new ExpressionReplacer(replaceMap).Visit(expr);
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}
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public static Expression GetBody(LambdaExpression lambda, params Expression[] toReplace)
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{
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if (lambda.Parameters.Count != toReplace.Length)
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throw new InvalidOperationException();
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return new ExpressionReplacer(Enumerable.Range(0, lambda.Parameters.Count)
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.ToDictionary(i => (Expression)lambda.Parameters[i], i => toReplace[i])).Visit(lambda.Body);
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}
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}
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}
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}
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