c#webservice中如何把对方传过来的inputstream类型转成string类型

[WebMethod]  
public void SendXml()  
{  
    // 获得客户端RAW HttpRequest  
    var inputStream = HttpContext.Current.Request.InputStream;  
    // 定义Response返回的格式是:Json  
    var response = HttpContext.Current.Response;  
    response.ContentType = "text/json";  
    //var strXml = "";  
    //using (var sr = new StreamReader(inputStream))  
    //    strXml = sr.ReadToEnd();  
    try  
    {  
        DataTable data = new DataTable();  
        using (var xr = XmlReader.Create(inputStream))  
            data.ReadXml(xr);  
        // 将读入Xml的DataTable的行数返回客户端  
        string count = "/"" + data.Rows.Count + "/"";  
        response.BinaryWrite(System.Text.Encoding.UTF8.GetBytes(count));  
    }  
    catch (Exception ex)  
    {  
        response.BinaryWrite(System.Text.Encoding.UTF8.GetBytes(ex.Message));  
    }  
}