Data AnnotationAttirbute to validate that value is one one of given stings strings

OneOfAttribute.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Diagnostics.CodeAnalysis;
using System.Linq;

namespace .DataValidation
{
    /// <inheritdoc />
    /// <summary>
    /// Validates that string is one of the given ones: 
    /// </summary>
    /// <example>
    ///  <code>
    ///     [OneOf("A","B","C")]
    ///     [OneOf("A","B","C","Value2", CaseSensitive = false)]
    /// </code>
    /// </example>
    [SuppressMessage("ReSharper", "ConvertToAutoProperty")]
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
    public class OneOfAttribute : ValidationAttribute
    {
        private readonly string[] _stringValues;
        

        public OneOfAttribute(params string[] stringValues)
        {
            _stringValues = stringValues;
        }
      

        public bool CaseSensitive { get; set; } = true;
        

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            if (validationContext.ObjectType != typeof(string))
            {
                return new ValidationResult($"'{validationContext.DisplayName}' is not of the string type");
            }
            if (_stringValues.Length == 0)
            {
                return new ValidationResult($"{this.GetType().Name} Validdation attribute on property '{validationContext.DisplayName}' has no allowed values provided.");
            }
            
            string s = value.ToString();
            StringComparison comparisionMethod = CaseSensitive ? StringComparison.InvariantCulture : StringComparison.InvariantCultureIgnoreCase;
            
          
            return new ValidationResult($"'{validationContext.DisplayName}' value should be one of the following: '{string.Join("', '", _stringValues)}'");
        }
    }
}

OneOfAttribute.Test.cs

using DataValidation;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace CHR.API.Provisioning.ATT.Web.Tests
{
    [TestClass]
    public class OneOfValidationTests
    {
        [TestMethod]
        public void OneOfAttribute_Should_Validate_Test()
        {
            //Arrange
            var attributeValue = "test";
            var validationAttribute = new OneOfAttribute("test", "test1", "test2");

            //Act
            var isValid = validationAttribute.IsValid(attributeValue);

            //Assert
            Assert.IsTrue(isValid);
        }

        [TestMethod]
        public void OneOfAttribute_Should_Not_Validate_Test()
        {
            //Arrange
            var attributeValue = "TEST";
            var validationAttribute = new OneOfAttribute("test", "test1", "test2");

            //Act
            var isValid = validationAttribute.IsValid(attributeValue);

            //Assert
            Assert.IsFalse(isValid);
        }

        [TestMethod]
        public void OneOfAttribute_With_NonCaseSensitiveValue_Separator_Should_Validate_test()
        {
            //Arrange
            var attributeValue = "test";
            var validationAttribute = new OneOfAttribute("TEST", "TESTING", "TESTED") {CaseSensitive = false};

            //Act
            var isValid = validationAttribute.IsValid(attributeValue);

            //Assert
            Assert.IsTrue(isValid);
        }
    }
}