Sure. Here an example that follows the same pattern for the existing ToLowerAttribute and ToUpperAttribute.

using System;
using System.Globalization;

namespace Dado.ComponentModel.DataMutations
{
	[AttributeUsage(AttributeTargets.Property)]
	public class ToTitleCaseAttribute : MutationAttribute
	{
		public CultureInfo CultureInfo { get; set; } = CultureInfo.CurrentCulture;
		public override int Priority { get; set; } = 40;

		protected override object MutateValue(object value, IMutationContext context)
		{
			if (value is string valueAsString && !String.IsNullOrWhiteSpace(valueAsString)) {
				return CultureInfo.TextInfo.ToTitleCase(valueAsString);
			}

			if (value is char valueAsChar) {
				return CultureInfo.TextInfo.ToTitleCase();
			}

			return value;
		}
	}
}

This should probably be including in this package.

Originally posted by @roydukkey in #16 (comment)

This attribute would ensure the value is within the bounds of a numeric range.

Determine Numeric Range Value
The range value should be determined firstly by the attribute's own value via the constructor or property. Should the attribute not specify a value, a RangeAttribute attribute would be sought.

Research
It is not yet determined if the range values should be including or exclude as part of the acceptable range. This behaviour will be determine bases on the function on the RangeAttribute.

Hi,
id like to know if its possible mutates value of property:

• First char like Uppercase
• The others chars in lowercase
  f.i. : the REAL thing ===> The real thing

thanks in advance

This attribute would ensure the length of a string, array, or IEnumerable is not greater than a maximum length.

Determine Maximum Length Value
The maximum length should be determined firstly by the attribute's own value via the constructor or property. Should the attribute not specify a value, a MaxLengthAttribute attribute would be sought. And lastly, when the value being mutated is a string, the StringLengthAttribute will be used.

EnsureMinLength
An equivalent attribute for minimum length will not be made. Such an attribute would be too opinionated as it would need to accept a value/s that would be used fill any empty positions. Instead a IMutableObject interface or custom MutationAttribute is more suitable.

Fixup weird Array casting dead code in Min/MaxLengthAttribute. dotnet/corefx@6259768

Since the MutationContext<T> is not injectible into my code because of the ctor, I cant Moq it or test it.

IE:

.AddSingleton<MutationContext<Customer>>()

Later:

public class CustomerRepository
{
    public MutationContext<Customer> customerMutationContext { get; set; }

    public CustomerRepository(MutationContext<Customer> customerMutationContext)
    {
        this.customerMutationContext = customerMutationContext;
    }

    public void SaveCustomer(Customer cust)
    {
        this.customerMutationContext.Init(cust).Mutate();
    }
}

Namespace should change from System.ComponentModel.DataMutations to Dado.ComponentModel.DataMutations and likewise for package name.

Add support for a fluent API much like Entity Framework's Fluent API.

dotnet/corefx@e1fe073

The ToDefaultValueAttribute throws an exception when trying to evaluate null value.

This is a pretty cool library, thanks! What's not clear to me though is, what actually triggers the mutation since this isn't a normal ability of an Attribute.

1. • dotnet/corefx@121d871
2. • dotnet/corefx@4721339
3. • dotnet/corefx@032f379
4. • dotnet/corefx@240471d
5. • dotnet/corefx@24110b6
6. • dotnet/corefx@c4bb8b7
7. • dotnet/corefx@8b04d0a

dotnet/corefx@f0d822b

Review dotnet/corefx#16305