升级2sxc至v14后Convert.FromBase64String无法正常工作

问题背景 #

升级自定义2sxc API至v14版本后，文件上传控制器中Base64转字节数组功能失效。原代码如下：

public class IntegrationApiController : Custom.Hybrid.Api14
{
    [HttpPost]
    public string UploadPdf([FromBody] dynamic bodyJson)
    {
        var entity = new Dictionary<string, object>();
        var guid = Guid.NewGuid();
        entity.Add("EntityGuid", guid);
        App.Data.Create("PDFForm", entity);
        var data = Convert.FromBase64String(bodyJson.file.ToString());
        var returnThing = SaveInAdam(stream: new MemoryStream(data), fileName: bodyJson.fileName.ToString(), contentType: "PDFForm", guid: guid, field: "File");
        
        return returnThing.Url;
    }
}

首次报错信息：

{
    "Message": "2sxc Api Controller Finder Error: Error selecting / compiling an API controller. Check event-log, code and inner exception. ",
    "ExceptionMessage": "c:\\Websites\\Mainstar\\Portals\\0\\2sxc\\DocusignForms\\api\\IntegrationApiController.cs(26): error CS1061: 'ToSic.Sxc.Services.IConvertService' does not contain a definition for 'FromBase64String' and no extension method 'FromBase64String' accepting a first argument of type 'ToSic.Sxc.Services.IConvertService' could be found (are you missing a using directive or an assembly reference?)",
    "ExceptionType": "System.Web.HttpCompileException",
    "StackTrace": "   at System.Web.Compilation.AssemblyBuilder.Compile()\r\n   at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()\r\n   at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath)\r\n   at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate)\r\n   at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate)\r\n   at System.Web.Compilation.BuildManager.GetVPathBuildResult(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean ensureIsUpToDate)\r\n   at System.Web.Compilation.BuildManager.GetCompiledAssembly(String virtualPath)\r\n   at ToSic.Sxc.Dnn.WebApiRouting.AppApiControllerSelector.HttpControllerDescriptor(HttpRequestMessage request, String controllerFolder, String controllerPath, String controllerTypeName, LogCall`1 wrapLog) in C:\\Projects\\2sxc\\2sxc\\Src\\Dnn\\ToSic.Sxc.Dnn.WebApi\\Dnn\\WebApiRouting\\AppApiControllerSelector.cs:line 168\r\n   at ToSic.Sxc.Dnn.WebApiRouting.AppApiControllerSelector.SelectController(HttpRequestMessage request) in C:\\Projects\\2sxc\\2sxc\\Src\\Dnn\\ToSic.Sxc.Dnn.WebApi\\Dnn\\WebApiRouting\\AppApiControllerSelector.cs:line 83"
}

改为System.Convert.FromBase64String后，出现新错误：Cannot perform runtime binding on a null reference

错误原因 #

1. 命名冲突：Api14控制器内置了Convert服务（属于ToSic.Sxc.Services.IConvertService），直接使用Convert.FromBase64String会调用该服务，而非.NET原生的System.Convert，导致找不到方法。
2. 空引用问题：使用dynamic参数无法确保请求体中的file和fileName字段存在，若请求格式不正确或字段缺失，调用ToString()时会触发空引用异常。

解决步骤 #

1. 完全限定.NET原生Convert命名空间 #

明确使用System.Convert.FromBase64String，避免与2sxc内置服务冲突。

2. 替换dynamic为强类型模型 #

定义强类型类接收请求体，确保参数类型安全，同时便于验证输入是否有效。

3. 添加参数验证 #

在处理前检查关键参数是否为空，提前抛出明确的错误信息。

完整修正代码 #

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Web.Http;

public class IntegrationApiController : Custom.Hybrid.Api14
{
    // 定义强类型模型接收请求体
    public class PdfUploadRequest
    {
        public string File { get; set; }
        public string FileName { get; set; }
    }

    [HttpPost]
    public IHttpActionResult UploadPdf([FromBody] PdfUploadRequest request)
    {
        // 参数验证
        if (request == null || string.IsNullOrEmpty(request.File) || string.IsNullOrEmpty(request.FileName))
        {
            return BadRequest("请求参数不完整，必须包含File（Base64字符串）和FileName字段");
        }

        try
        {
            var guid = Guid.NewGuid();
            
            // 创建PDFForm实体
            var entity = new Dictionary<string, object>
            {
                { "EntityGuid", guid }
            };
            App.Data.Create("PDFForm", entity);

            // 使用System.Convert转换Base64为字节数组
            var data = System.Convert.FromBase64String(request.File);
            var adamResult = SaveInAdam(
                stream: new MemoryStream(data), 
                fileName: request.FileName, 
                contentType: "PDFForm", 
                guid: guid, 
                field: "File");

            return Ok(new { Url = adamResult.Url });
        }
        catch (FormatException ex)
        {
            return BadRequest($"Base64格式错误：{ex.Message}");
        }
        catch (Exception ex)
        {
            return InternalServerError(ex);
        }
    }
}

额外说明 #

• 强类型模型确保请求体字段与代码预期一致，避免dynamic类型的隐式转换问题。
• 参数验证和异常捕获能返回更清晰的错误信息，便于调试和前端处理。
• 始终使用System.Convert而非简写的Convert，避免与2sxc内置服务命名冲突。

内容的提问来源于stack exchange，提问作者John K.