114 lines
3.1 KiB
C#
114 lines
3.1 KiB
C#
// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
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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 Microsoft.AspNet.Http;
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using Microsoft.AspNet.Routing;
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namespace InlineConstraintSample.Web.Constraints
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{
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public class IsbnDigitScheme10Constraint : IRouteConstraint
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{
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private readonly bool _allowDashes;
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public IsbnDigitScheme10Constraint(bool allowDashes)
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{
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_allowDashes = allowDashes;
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}
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public bool Match(
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HttpContext httpContext,
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IRouter route,
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string routeKey,
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IDictionary<string, object> values,
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RouteDirection routeDirection)
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{
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object value;
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if (!values.TryGetValue(routeKey, out value))
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{
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return false;
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}
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var inputString = value as string;
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string isbnNumber;
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if (inputString == null
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|| !TryGetIsbn10(inputString, _allowDashes, out isbnNumber))
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{
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return false;
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}
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var sum = 0;
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Func<char, int> convertToInt = (char n) => n - '0';
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for (int i = 0; i < isbnNumber.Length - 1; ++i)
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{
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sum += convertToInt(isbnNumber[i]) * (i + 1);
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}
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var checkSum = sum % 11;
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var lastDigit = isbnNumber.Last();
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if (checkSum == 10)
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{
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return char.ToUpperInvariant(lastDigit) == 'X';
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}
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else
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{
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return checkSum == convertToInt(lastDigit);
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}
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}
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private static bool TryGetIsbn10(string value, bool allowDashes, out string isbnNumber)
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{
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if (!allowDashes)
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{
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if (CheckIsbn10Characters(value))
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{
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isbnNumber = value;
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return true;
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}
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else
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{
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isbnNumber = null;
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return false;
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}
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}
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var isbnParts = value.Split(
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new char[] { '-' },
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StringSplitOptions.RemoveEmptyEntries);
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if (isbnParts.Length == 4)
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{
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value = value.Replace("-", string.Empty);
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if (CheckIsbn10Characters(value))
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{
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isbnNumber = value;
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return true;
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}
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}
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isbnNumber = null;
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return false;
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}
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private static bool CheckIsbn10Characters(string value)
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{
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if (value.Length != 10)
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{
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return false;
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}
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var digits = value.Substring(0, 9);
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var checksum = value.Last();
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return digits.All(n => '0' <= n && n <= '9')
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&& ('0' <= checksum && checksum <= '9'
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|| 'X' == char.ToUpperInvariant(checksum));
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}
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}
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} |