C#微信解密用户数据出现问题 Specified initialization vector (IV) does not match the block size for this algorithm

Question

问题遇到的现象和发生背景

dotnet C#微信解密用户数据出现问题 Specified initialization vector (IV) does not match the block size for this algorithm

用代码块功能插入代码，请勿粘贴截图

官方的文档https://developers.weixin.qq.com/miniprogram/dev/api-backend/open-api/internet/internet.getUserEncryptKey.html#Object

官方文档看得也是一头雾水

微信返回的参数↓

encryptedData

Tx4IRbJW27WkElNq4zwlCA==

encryptIv

af1aa212da60282a

sessionKey

m6cs73i3dt+kEsZV+UbdaA==

解密的代码↓

public static string Decrypt(string encryptedData, string encryptIv, string sessionKey)
        {
            //base64解码为字节数组
            var encryptData = Convert.FromBase64String(encryptedData);
            var key = Convert.FromBase64String(sessionKey);
            var iv = Convert.FromBase64String(encryptIv);

            //创建aes对象
            var aes = Aes.Create();

            if (aes == null)
            {
                throw new InvalidOperationException("未能获取Aes算法实例");
            }
            //设置模式为CBC
            aes.Mode = CipherMode.CBC;
            //设置填充
            aes.Padding = PaddingMode.PKCS7;
            //设置Key大小
            aes.KeySize = 128;
            aes.Key = key;
            aes.IV = iv;

            //创建解密器
            var de = aes.CreateDecryptor();
            //解密数据
            var decodeByteData = de.TransformFinalBlock(encryptData, 0, encryptData.Length);
            //转换为字符串
            var data = Encoding.UTF8.GetString(decodeByteData);

            return data;
        }

不知道是不是我解密的方法写错了,但网上找了好几个,都是报这个错误,
iv不知道怎么去解

运行结果及报错内容

 System.Security.Cryptography.CryptographicException: Specified initialization vector (IV) does not match the block size for this algorithm.
         at System.Security.Cryptography.SymmetricAlgorithm.set_IV(Byte[] value)
         at BHH.Controllers.OpenController.WechatDecrypt(String encryptedData, String encryptIv, String sessionKey) in D:\Code\BHH\BHH\Controllers\OpenController.cs:line 136
         at BHH.Controllers.OpenController.WechatMp(String code) in D:\Code\BHH\BHH\Controllers\OpenController.cs:line 101
         at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Logged|12_1(ControllerActionInvoker invoker)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
         at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
         at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
         at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

我的解答思路和尝试过的方法

我想要达到的结果

解密出数据