向某个url提交数据并读取该地址返回的xml,并将xml转换成dataset,并返回dataset中某个表

/// <summary>
/// 向某个url提交数据并读取该地址返回的xml,并将xml转换成dataset,并返回dataset中某个表
/// </summary>
/// <param name="url">提交的低至</param>
/// <param name="param">参数</param>
/// <param name="tableName">表名</param>
/// <returns></returns>
public static DataTable PostData(string url, string param, String tableName)
{
#region post数据

DataSet ds = new DataSet();
DataTable dt = new DataTable();
HttpWebRequest req = (HttpWebRequest) WebRequest.Create(url);
req.Timeout = 120000;
byte[] requestbytes = System.Text.Encoding.ASCII.GetBytes(param);
req.Method = "post";
req.ContentType = "application/x-www-form-urlencoded";
req.ContentLength = requestbytes.Length;
System.IO.Stream requeststream = req.GetRequestStream();
requeststream.Write(requestbytes, 0, requestbytes.Length);
requeststream.Close();
HttpWebResponse res = (HttpWebResponse) req.GetResponse();
System.IO.StreamReader sr = new System.IO.StreamReader(res.GetResponseStream(), System.Text.Encoding.Default);

String backstr = sr.ReadToEnd();
StringReader txtReader = new StringReader(backstr);
XmlTextReader xmlReader = new XmlTextReader(txtReader);
try
{
ds.ReadXml(xmlReader);
}
catch
{
return null;
}
sr.Close();
res.Close();
sr.Dispose();

//条件判断
if (ds != null && ds.Tables.Count > 0 && ds.Tables[tableName] != null)
{
dt = ds.Tables[tableName].Copy();
}
return dt;

#endregion
}