1. 在Models文件夹中创建一个名为CustomEmailValidationAttribute.cs的类，并继承ValidationAttribute类。在重写IsValid方法之前，我们需要创建一个接口IValidationAttributeAdapterProvider以确保MVC系统可以解析自定义验证器。

using System.ComponentModel.DataAnnotations; using Microsoft.AspNetCore.Mvc.DataAnnotations; using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;

public class CustomEmailValidationAttribute : ValidationAttribute, IValidationAttributeAdapterProvider { private string _allowedDomain;

public CustomEmailValidationAttribute(string allowedDomain)
{
    _allowedDomain = allowedDomain;
    ErrorMessage = $"Email domain must be '{_allowedDomain}'";
}

protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
    if (value != null)
    {
        var email = value.ToString().ToLower();
        if (email.EndsWith($"@{_allowedDomain}"))
        {
            return ValidationResult.Success;
        }
    }
    return new ValidationResult(ErrorMessage);
}

public IAttributeAdapter GetAttributeAdapter(ValidationAttribute attribute, IStringLocalizer stringLocalizer)
{
    return new CustomEmailValidationAttributeAdapter((CustomEmailValidationAttribute)attribute, stringLocalizer);
}

}

2. 实现上一步中引用的IAttributeAdapter接口。创建名为CustomEmailValidationAttributeAdapter.cs的类并继承AttributeAdapterBase类。

using System.ComponentModel.DataAnnotations; using Microsoft.AspNetCore.Mvc.DataAnnotations; using Microsoft.AspNetCore.Mvc.ModelBinding.Validation; using Microsoft.Extensions.Localization;

public class CustomEmailValidationAttributeAdapter : AttributeAdapterBase { public CustomEmailValidationAttributeAdapter(CustomEmailValidationAttribute attribute, IStringLocalizer stringLocalizer) : base(attribute, stringLocalizer) { }

public override void AddValidation(ClientModelValidationContext context)
{
    MergeAttribute(context.Attributes, "data-val", "true");
    MergeAttribute(context.Attributes, "data-val-customemail", GetErrorMessage(context));
    MergeAttribute(context.Attributes, "data-val-customemail-domain", Attribute._allowedDomain);
}

public override string GetErrorMessage(ModelValidationContextBase validationContext)
{
    return Attribute.ErrorMessage;
}

private bool MergeAttribute(IDictionary attributes, string key, string value)