[API Proposal]: Add a RangeAttribute constructor supporting arbitrary IComparable ranges.

[eiriktsarpalis]

Background and motivation

The RangeAttribute currently supports int and double ranges out of the box using dedicated constructor overloads, however any other range necessitates using this overload requiring the operand type as well as string formatted representations of the lower and upper bounds. This only works for types supported by the TypeConverter class expressing limits in strings forces concerns around culture-sensitive formatting:

public class TimeSpanRangeAttribute : RangeAttribute
{
    public TimeSpanRangeAttribute(int minMilliseconds, int maxMilliseconds)
        : base(type: typeof(TimeSpan),
               minimum: TimeSpan.FromMilliseconds(minMilliseconds).ToString("c"),
               maximum: TimeSpan.FromMilliseconds(maxMilliseconds).ToString("c"))
    {
        ParseLimitsInInvariantCulture = true;
    }
}

I've been working on a prototype that adds a protected constructor which accepts arbitrary IComparable bounds directly.

API Proposal

namespace System.ComponentModel.DataAnnotations;

public partial class RangeAttribute
{
    public RangeAttribute(int minimum, int maximum);
    public RangeAttribute(double minimum, double maximum);
+   public RangeAttribute(IComparable minimum, IComparable maximum);

    [RequiresUnreferencedCode("Generic TypeConverters may require the generic types to be annotated.")]
    public RangeAttribute(Type type, string minimum, string maximum);
}

API Usage

The above example is now rendered as follows:

public class TimeSpanMillisecondRangeAttribute : RangeAttribute
{
    public TimeSpanMillisecondRangeAttribute(int minimumMs, int maximumMs)
        : base(TimeSpan.FromMilliseconds(minimumMs), TimeSpan.FromMilliseconds(maximumMs))
    { }
}

Alternative Designs

• I marked the proposed constructor as protected, since marking it public would add OOTB support for things like string or long ranges using their built-in IComparable implementation. Marking it protected emphasizes its use as an extensibility point for user-defined derived validation attributes. If people thinks it is useful, we could mark as public instead.
• Proposal leaves out IComparer support since the validator implementation is oriented around handling of IComparable values.

Risks

No response

cc @geeknoid @jeffhandley

[ghost]

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Background and motivation

The RangeAttribute currently supports int and double ranges out of the box using dedicated constructor overloads, however any other range necessitates using this overload requiring the operand type as well as string formatted representations of the lower and upper bounds. This only works for types supported by the TypeConverter class expressing limits in strings forces concerns around culture-sensitive formatting:

public class TimeSpanRangeAttribute : RangeAttribute
{
    public TimeSpanRangeAttribute(int minMilliseconds, int maxMilliseconds)
        : base(type: typeof(TimeSpan),
               minimum: TimeSpan.FromMilliseconds(minMilliseconds).ToString("c"),
               maximum: TimeSpan.FromMilliseconds(maxMilliseconds).ToString("c"))
    {
        ParseLimitsInInvariantCulture = true;
    }
}

I've been working on a prototype that adds a protected constructor which accepts arbitrary IComparable bounds directly.

API Proposal

namespace System.ComponentModel.DataAnnotations;

public partial class RangeAttribute
{
    public RangeAttribute(int minimum, int maximum);
    public RangeAttribute(double minimum, double maximum);
+   protected RangeAttribute(IComparable minimum, IComparable maximum);

    [RequiresUnreferencedCode("Generic TypeConverters may require the generic types to be annotated.")]
    public RangeAttribute(Type type, string minimum, string maximum);
}

API Usage

The above example is now rendered as follows:

public class TimeSpanMillisecondRangeAttribute : RangeAttribute
{
    public TimeSpanMillisecondRangeAttribute(int minimumMs, int maximumMs)
        : base(TimeSpan.FromMilliseconds(minimumMs), TimeSpan.FromMilliseconds(maximumMs))
    { }
}

Alternative Designs

• I marked the proposed constructor as protected, since marking it public would add OOTB support for things like string or long ranges using their built-in IComparable implementation. Marking it protected emphasizes its use as an extensibility point for user-defined derived validation attributes. If people thinks it is useful, we could mark as public instead.
• Proposal leaves out IComparer support since the validator implementation is oriented around handling of IComparable values.

Risks

No response

cc @geeknoid @jeffhandley

Author:	eiriktsarpalis
Assignees:	-
Labels:	api-suggestion, area-System.Runtime
Milestone:	Future

[ghost]

Tagging subscribers to this area: @ajcvickers, @bricelam, @roji
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Background and motivation

The RangeAttribute currently supports int and double ranges out of the box using dedicated constructor overloads, however any other range necessitates using this overload requiring the operand type as well as string formatted representations of the lower and upper bounds. This only works for types supported by the TypeConverter class expressing limits in strings forces concerns around culture-sensitive formatting:

public class TimeSpanRangeAttribute : RangeAttribute
{
    public TimeSpanRangeAttribute(int minMilliseconds, int maxMilliseconds)
        : base(type: typeof(TimeSpan),
               minimum: TimeSpan.FromMilliseconds(minMilliseconds).ToString("c"),
               maximum: TimeSpan.FromMilliseconds(maxMilliseconds).ToString("c"))
    {
        ParseLimitsInInvariantCulture = true;
    }
}

I've been working on a prototype that adds a protected constructor which accepts arbitrary IComparable bounds directly.

API Proposal

namespace System.ComponentModel.DataAnnotations;

public partial class RangeAttribute
{
    public RangeAttribute(int minimum, int maximum);
    public RangeAttribute(double minimum, double maximum);
+   protected RangeAttribute(IComparable minimum, IComparable maximum);

    [RequiresUnreferencedCode("Generic TypeConverters may require the generic types to be annotated.")]
    public RangeAttribute(Type type, string minimum, string maximum);
}

API Usage

The above example is now rendered as follows:

public class TimeSpanMillisecondRangeAttribute : RangeAttribute
{
    public TimeSpanMillisecondRangeAttribute(int minimumMs, int maximumMs)
        : base(TimeSpan.FromMilliseconds(minimumMs), TimeSpan.FromMilliseconds(maximumMs))
    { }
}

Alternative Designs

• I marked the proposed constructor as protected, since marking it public would add OOTB support for things like string or long ranges using their built-in IComparable implementation. Marking it protected emphasizes its use as an extensibility point for user-defined derived validation attributes. If people thinks it is useful, we could mark as public instead.
• Proposal leaves out IComparer support since the validator implementation is oriented around handling of IComparable values.

Risks

No response

cc @geeknoid @jeffhandley

Author:	eiriktsarpalis
Assignees:	-
Labels:	api-suggestion, area-System.ComponentModel.DataAnnotations, area-System.Runtime
Milestone:	Future

[jeffhandley]

@eiriktsarpalis I'm inclined to pull this into .NET 8 to group it with the other DataAnnotations enhancements we're making during the release. @geeknoid Would you be able to use this if it was in .NET 8?

/cc @dotnet/area-system-componentmodel-dataannotations

[eiriktsarpalis]

Sure, marking as ready for review.

[geeknoid]

@jeffhandley Yes, I think we could use this in .NET 8

[terrajobst]

• We suggest to provide a RangeAttribute<T> that is abstract and constrains the parameters to have the same type.
• We should consider a design where RangeAttribute<T> doesn't extend RangeAttribute such that we can constrain T to IComparable<T> rather than IComparable.

namespace System.ComponentModel.DataAnnotations;

public partial class RangeAttribute
{
    // Existing:
    // public RangeAttribute(int minimum, int maximum);
    // public RangeAttribute(double minimum, double maximum);
    private protected RangeAttribute(Type type, IComparable minimum, IComparable maximum);
}

public abstract class RangeAttribute<T> : RangeAttribute
    where T: IComparable
{
    protected RangeAttribute(T minimum, T maximum);
}

// Example usage:
// 
// public class TimeSpanMillisecondRangeAttribute : RangeAttribute<TimeSpan>
// {
//     public TimeSpanMillisecondRangeAttribute(int minimumMs, int maximumMs)
//         : base(TimeSpan.FromMilliseconds(minimumMs),
//                TimeSpan.FromMilliseconds(maximumMs))
//     {        
//     }
// }

[jeffhandley]

We will not pursue that revised design in .NET 8. Moving to Future and removing the blocking Marks issues that we want to fast track in order to unblock other important work label.

[eerhardt]

Could we also use the IParsable interface and create:

public sealed class ParsedRangeAttribute<T> : RangeAttribute<T> // this name could use some work
    where T : IComparable, IParsable<T>
{
    public ParsedRangeAttribute(string minimum, string maximum);
}

Then users wouldn't need to create their own derived attribute classes to use types that are IParsable, like TimeSpan.

Regarding naming, I think it would make more sense to use the Range<T> attribute name for the sealed class - the one that would be used in all the callsites. So maybe it would make sense to say:

public abstract class ComparableRangeAttribute<T> : RangeAttribute
    where T : IComparable
{
    protected ComparableRangeAttribute(T minimum, T maximum);
}

public sealed class RangeAttribute<T> : ComparableRangeAttribute<T>
    where T : IComparable, IParsable<T>
{
    public RangeAttribute(string minimum, string maximum);
}

And then usages would look like:

public class ResilienceStrategyOptions
{
    [Range<TimeSpan>("00:00:00", "1.00:00:00")]
    public TimeSpan? MaxDelay { get; set; }
}