Web API Post对象在其内容大约为1 GB或更多时变为null

Question

当内容长度大约为600MB时，一切都按预期工作，当它接近1GB或更高时，实体在Web API处变为null。

这是MVC客户端代码，它调用Web API：

`$query="insert into student_info (NAME, MATHS, GEOGRAPHY, ENGLISH)  VALUES ('$name','$maths','$geog','$english')";


 if (mysql_query($query))
 {
   echo "<b>";
   echo "<h3>";
   echo "RECORD ADDED ";
   echo "<h3>";
   echo "</b>";
 }
   else
 {
 echo "<b>";
 echo "<h3>";
 echo "RECORD NOT ENTERED SOMETHING WENT WRONG";
 echo "</h3>";
 echo "</b>";
 echo "<br>";
 echo mysql_error();
  }
 ?>

以下是网址API代码：

using (var client = new HttpClient(new HttpClientHandler()))
{
    client.BaseAddress = new Uri(_serviceRootUrl);
    client.DefaultRequestHeaders.Accept.Clear();
    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
    return await client.PostAsJsonAsync(controlActionPath, entityObject);
}

这是DocumentDto类的代码：

[Route("Upload")]
[HttpPost]
public void Upload(DocumentDto entity)
{
    var dbEntity = new DocumentDto
    {
        AddBy = entity.AddBy,
        AddOn = DateTime.Now
    };           
}

Web.config是：

public class DocumentDto
{
    public int DocumentSeqId { get; set; }
    public byte[] Content { get; set; }
    public int AddBy { get; set; }
    public DateTime AddOn { get; set; }
}

如果我可以提供任何其他信息，请告诉我。