csharp 数据注释属性，用于验证字符串是否为有效的XML

Posted 2021-05-12

using System.ComponentModel.DataAnnotations;
using System.Xml;

namespace CHR.API.Provisioning.ATT.BusinessLogic.DataValidation
{
    /// <inheritdoc />
    /// <summary>
    /// Data annotation attribute to verify that string is a valid XML
    /// </summary>
    public class ValidXml : ValidationAttribute
    {
        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            if (!(value is string))
            {
                return new ValidationResult($"'{validationContext.MemberName}' property of '{validationContext.ObjectType.Name}' class is not a string property.");
            }
            var xmlString = (string) value;
            try
            {
                // Check we actually have a value
                if (string.IsNullOrEmpty(xmlString) == false)
                {
                    // Try to load the value into a document
                    var xmlDoc = new XmlDocument();

                    xmlDoc.LoadXml(xmlString);

                    // If we managed with no exception then this is valid XML!
                    return ValidationResult.Success;
                }
                // A blank value is not valid xml
                return new ValidationResult($"'{validationContext.MemberName}' is an empty string.");
            }
            catch (XmlException)
            {
                return new ValidationResult($"'{validationContext.MemberName}' is not a valid XML.");
            }
        }
    }
}