ASP.NET MVC5，当JSON无效时如何获取原始JSON/request-body-content？

public IActionResult MyMethod([FromBody] MyModel model)
{
    // 处理接收到的JSON数据
    // ...
}

using (var reader = new StreamReader(Request.Body))
{
    var requestBody = await reader.ReadToEndAsync();
    // 处理原始请求体内容
    // ...
}

using (var reader = new StreamReader(Request.Body))
{
    var contentLength = (int)Request.ContentLength;
    var buffer = new char[contentLength];
    await reader.ReadAsync(buffer, 0, contentLength);
    var requestBody = new string(buffer);
    // 处理原始JSON
    // ...
}