LogLevelTypeConverter.cs

// 
// Copyright (c) 2004-2019 Jaroslaw Kowalski <jaak@jkowalski.net>, Kim Christensen, Julian Verdurmen
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions 
// are met:
// 
// * Redistributions of source code must retain the above copyright notice, 
//   this list of conditions and the following disclaimer. 
// 
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution. 
// 
// * Neither the name of Jaroslaw Kowalski nor the names of its 
//   contributors may be used to endorse or promote products derived from this
//   software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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namespace NLog.Attributes
{
    using System;
    using System.ComponentModel;
    using System.Globalization;

    /// <summary>
    /// Support <see cref="NLog.LogLevel"/> implementation of <see cref="IConvertible"/>
    /// </summary>
    public class LogLevelTypeConverter : TypeConverter
    {
        /// <inheritdoc/>
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            return sourceType == typeof(string) || IsNumericType(sourceType) || base.CanConvertFrom(context, sourceType);
        }

        /// <inheritdoc/>
        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value?.GetType() == typeof(string))
                return LogLevel.FromString(value.ToString());
            else if (IsNumericType(value?.GetType()))
                return LogLevel.FromOrdinal(Convert.ToInt32(value));
            else 
                return base.ConvertFrom(context, culture, value);
        }

        /// <inheritdoc/>
        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            return destinationType == typeof(string) || IsNumericType(destinationType) || base.CanConvertTo(context, destinationType);
        }

        /// <inheritdoc/>
        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (value is LogLevel logLevel)
            {
                if (destinationType == typeof(string))
                    return logLevel.ToString();
                else if (IsNumericType(destinationType))
                    return Convert.ChangeType(logLevel.Ordinal, destinationType, culture);
            }
            return base.ConvertTo(context, culture, value, destinationType);
        }

        private static bool IsNumericType(Type sourceType)
        {
            return sourceType == typeof(int) ||
                sourceType == typeof(uint) ||
                sourceType == typeof(long) ||
                sourceType == typeof(ulong) ||
                sourceType == typeof(short) ||
                sourceType == typeof(ushort);
        }
    }
}