<PackageReference Include="System.ComponentModel.Annotations" Version="5.0.0-preview.8.20407.11" />

System.ComponentModel.DataAnnotations.ValidationAttribute

public abstract class ValidationAttribute : Attribute
Serves as the base class for all validation attributes.
namespace System.ComponentModel.DataAnnotations { public abstract class ValidationAttribute : Attribute { protected string ErrorMessageString { get; } public virtual bool RequiresValidationContext { get; } public string ErrorMessage { get; set; } public string ErrorMessageResourceName { get; set; } public Type ErrorMessageResourceType { get; set; } protected ValidationAttribute(); protected ValidationAttribute(string errorMessage); protected ValidationAttribute(Func<string> errorMessageAccessor); public virtual string FormatErrorMessage(string name); public virtual bool IsValid(object value); protected virtual ValidationResult IsValid(object value, ValidationContext validationContext); public ValidationResult GetValidationResult(object value, ValidationContext validationContext); public void Validate(object value, string name); public void Validate(object value, ValidationContext validationContext); } }