CompareNum.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;
using System.Globalization;
using System.Windows.Data;

namespace SiliconStudio.Presentation.ValueConverters
{
    /// <summary>
    /// This converter will compare a given numeric value with a numeric value passed as parameter.
    /// </summary>
    public abstract class CompareNum<T> : OneWayValueConverter<T> where T : class, IValueConverter, new()
    {
        /// <inheritdoc/>
        public override object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var doubleValue = (double)System.Convert.ChangeType(value, typeof(double));
            var doubleParameter = (double)System.Convert.ChangeType(parameter, typeof(double));
            var result = Compare(doubleValue, doubleParameter);
            return System.Convert.ChangeType(result, value.GetType());
        }

        protected abstract bool Compare(double left, double right);
    }

    /// <summary>
    /// This converter will return <c>true</c> if the numeric value is greater than the numeric parameter.
    /// </summary>
    public class IsGreater : CompareNum<IsGreater>
    {
        protected override bool Compare(double left, double right)
        {
            return left > right;
        }
    }

    /// <summary>
    /// This converter will return <c>true</c> if the numeric value is lower than the numeric parameter.
    /// </summary>
    public class IsLower : CompareNum<IsLower>
    {
        protected override bool Compare(double left, double right)
        {
            return left < right;
        }
    }

    /// <summary>
    /// This converter will return <c>true</c> if the numeric value is greater than or equal to the numeric parameter.
    /// </summary>
    public class IsGreaterOrEqual : CompareNum<IsGreaterOrEqual>
    {
        protected override bool Compare(double left, double right)
        {
            return left >= right;
        }
    }

    /// <summary>
    /// This converter will return <c>true</c> if the numeric value is lower than or equal to the numeric parameter.
    /// </summary>
    public class IsLowerOrEqual : CompareNum<IsLowerOrEqual>
    {
        protected override bool Compare(double left, double right)
        {
            return left <= right;
        }
    }

    /// <summary>
    /// This converter will return <c>true</c> if the numeric value is equal to the numeric parameter.
    /// </summary>
    public class IsEqual : CompareNum<IsEqual>
    {
        protected override bool Compare(double left, double right)
        {
            return Math.Abs(left - right) <= double.Epsilon;
        }
    }

    /// <summary>
    /// This converter will return <c>true</c> if the numeric value is different from the numeric parameter.
    /// </summary>
    public class IsDifferent : CompareNum<IsDifferent>
    {
        protected override bool Compare(double left, double right)
        {
            return Math.Abs(left - right) > double.Epsilon;
        }
    }
}