HTTP 429错误：Instagram远程服务器返回未知状态码（429）

I'm working on some new programs using my own instagram api.

Everything is working fine with me except following user script

i wanna follow my list of users id

so i use this code

foreach (var item in listBox1.Items)

{

WebRequest request = WebRequest.Create("https://api.instagram.com/v1/users/"+item+"/relationship?access_token=" + Common.token2);

request.Proxy = null;

request.Method = "POST";

string postData = "action=follow";

byte[] byteArray = Encoding.UTF8.GetBytes(postData);

// Set the ContentType property of the WebRequest.

request.ContentType = "application/x-www-form-urlencod