无法使用REST API在querystring中发布大型XML

我有一个rest api，我需要使用post方法发布一个大型xml。

我在inboundRequest参数下发布数据需求值的控制器。

当我像下面这样为小数据调用url时，代码工作得很好例如:http://localhost/api/GetXMl?inboundRequest="数据"，但不工作时，大XML发布:

更新代码:

 byte[] bytes;
    bytes = System.Text.Encoding.ASCII.GetBytes(input.value);
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://localhost/api/GETXMl?inboundRequest=" + input.value);
    string postData =  input.value;
    request.ContentType = "text/xml; encoding='utf-8'";
    request.ContentLength = bytes.Length;
    request.Method = "POST";
    request.Timeout = 1000000000;
    request.ReadWriteTimeout = 100000000;
    Stream requestStream = request.GetRequestStream();
    requestStream.Write(bytes, 0, bytes.Length);
    requestStream.Close();
    HttpWebResponse response;
    response = (HttpWebResponse)request.GetResponse();
    if (response.StatusCode == HttpStatusCode.OK)
    {
        Stream responseStream = response.GetResponseStream();
        string responseStr = new StreamReader(responseStream).ReadToEnd();
        return responseStr;
    }
    return null;

并得到错误->{"无法从传输连接读取数据:已建立的连接被主机中的软件中止。"}