System.ComponentModel.DataAnnotations provides attribute classes that are used to define metadata for ASP.NET MVC and ASP.NET data controls.

The namespace has new annotations and modifications to existing ones on .NET8.

Length

Specifies the minimum and maximum length of collection/string data allowed in a property.

[Length(1, 20)]
public string FirstName { get; set; }

[Length(1, 5)]
public List<string> Courses { get; set; }

Range

Specifies the numeric range constraints for the value of a data field. Now, you can specify whether the range values are inclusive or exclusive.

MinimumIsExclusive : Specifies whether validation should fail for values that are equal to Minimum.
MaximumIsExclusive : Specifies whether validation should fail for values that are equal to Maximum.

[Range(15, 25, MinimumIsExclusive = true, MaximumIsExclusive = true)]
public int Age { get; set; }

AllowedValues

Specifies a list of values that should be allowed in a property.

[AllowedValues("Freshman", "Sophomore", "Junior", "Senior")]
public string Grade { get; set; }

DeniedValues

Specifies a list of values that should not be allowed in a property.

[DeniedValues("123456", "qwerty")]
public string Password { get; set; }

Base64String

Specifies that a data field value is a well-formed Base64 string.

[Base64String]
public string Hash { get; set; }

Required

From the blogs, I see that RequiredAttribute has a new property, DisallowAllDefaultValues to exclude default values. However, I cannot see this new feature in the code and documentation. I guess, this was remove in the release.

Reference

https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.dataannotations?view=net-8.0

ibrahimuludag / dataannotations