ASP.NET MVC 3:在需要模型外部信息时验证模型

public class CustomValidationAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        var context = (ValidationContext)value;
        var model = context.ObjectInstance as YourModel;
        var externalInfo = context.Items["ExternalInfo"] as ExternalInfo;

        // 在这里使用模型和外部信息进行验证
        // 如果验证通过，则返回true，否则返回false
        return true;
    }
}

var externalInfo = new ExternalInfo();
ModelState.AddModelError("ExternalInfo", externalInfo);

@Html.ValidationMessage("ExternalInfo")

public class YourModel
{
    [CustomValidation(ErrorMessage = "Validation error message")]
    public string PropertyToValidate { get; set; }
}