DefaultValueTypeConverter.cs

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using System.ComponentModel;
using System.Globalization;
 
namespace System.Data;
 
internal sealed class DefaultValueTypeConverter : StringConverter
{
    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
    {
        if (destinationType == null)
        {
            throw new ArgumentNullException("destinationType");
        }
        if (destinationType == typeof(string))
        {
            if (value == null)
            {
                return "<null>";
            }
            if (value == DBNull.Value)
            {
                return "<DBNull>";
            }
        }
        return base.ConvertTo(context, culture, value, destinationType);
    }
 
    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        if (value != null && value.GetType() == typeof(string))
        {
            string a = (string)value;
            if (string.Equals(a, "<null>", StringComparison.OrdinalIgnoreCase))
            {
                return null;
            }
            if (string.Equals(a, "<DBNull>", StringComparison.OrdinalIgnoreCase))
            {
                return DBNull.Value;
            }
        }
        return base.ConvertFrom(context, culture, value);
    }
}