Converting to `DateOnly/TimeOnly` from string

[maxkoshevoi]

Related to: dotnet/aspnetcore#36511

Description

DateTime can be converted from string (TypeDescriptor.GetConverter(typeof(DateTime)).ConvertFromString("01.01.0001")), while DateOnly and TimeOnly cannot. This causes some issues. For example, if they are added as query parameters in Asp.Net, they would be represented as 6 and 5 fields respectively instead of one string field (see dotnet/aspnetcore#36511 for more info).

For now, I've created a NuGet with custom type converters to solve this: https://github.com/maxkoshevoi/DateOnlyTimeOnly.AspNet/tree/main/DateOnlyTimeOnly.AspNet/Converters/Type

Are there any plans to enable string to DateOnly/TimeOnly conversion?

Regression?

No

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Issue Details

---

Related to: dotnet/aspnetcore#36511

Description

DateTime can be converted from string (TypeDescriptor.GetConverter(typeof(DateTime)).ConvertFromString("01.01.0001")), while DateOnly and TimeOnly cannot. This causes some issues. For example, if they are added as query parameters in Asp.Net, they would be represented as 6 and 5 fields respectively instead of one string field (see dotnet/aspnetcore#36511 for more info).

For now, I've created a NuGet with custom type converters to solve this: https://github.com/maxkoshevoi/DateOnlyTimeOnly.AspNet/tree/main/DateOnlyTimeOnly.AspNet/Converters/Type

Are there any plans to enable string to DateOnly/TimeOnly conversion?

Regression?

No

Author:	maxkoshevoi
Assignees:	-
Labels:	area-System.Runtime, untriaged
Milestone:	-

[0xced]

It's a bummer that the DateOnly and TimeOnly type converters have been forgotten in .NET 6. But this is the perfect opportunity to use the new IParseable<TSelf> preview feature and create a generic type converter in a few lines of code.

Note that you'll have to add <EnablePreviewFeatures>true</EnablePreviewFeatures> in your csproj and add a reference to the System.Runtime.Experimental package. Make sure to use version 6.0.2-mauipre.1.22054.8. For some reason version 6.0.0 doesn't work whe using the .NET 6.0.101 SDK and produces the following error:

[CS0246] The type or namespace name 'IParseable<>' could not be found (are you missing a using directive or an assembly reference?

Here's how to implement the generic converter:

using System;
using System.ComponentModel;
using System.Globalization;

namespace SampleCode;

public class ParseableTypeConverter<T> : TypeConverter where T : IParseable<T>
{
    public static void Register()
    {
        TypeDescriptor.AddAttributes(typeof(T), new TypeConverterAttribute(typeof(ParseableTypeConverter<T>)));
    }

    public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
    {
        return sourceType == typeof(string) || base.CanConvertFrom(context, sourceType);
    }

    public override object? ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
    {
        if (value is string stringValue)
        {
            return T.Parse(stringValue, culture);
        }
        return base.ConvertFrom(context, culture, value);
    }
}

Then register DateOnly and TimeOnly converters globally:

ParseableTypeConverter<DateOnly>.Register();
ParseableTypeConverter<TimeOnly>.Register();

Of course, it would still be nice to have those converters built-in for .NET 7.

[martincostello]

For some reason version 6.0.0 doesn't work when using the .NET 6.0.101 SDK

#62840