PowerBI Rest API synchronous call in C#

Hi Everyone,

I want to refresh mutliple datasets synchornously using Rest API in C#. 2nd dataset refresh should be called only after 1st dataset refresh gets completed, Challenge which i face right now is, even before 1st gets completed, 2nd gets called and its getting SQL time out issue because of overload. 

1st dataset refresh takes minimum 30-45 mins and time might vary due to server load as well.  Please suggest how to handle this!!

foreach (var res in comparedResult)
{
HttpWebRequest request = System.Net.HttpWebRequest.CreateHttp(String.Format("https://api.powerbi.com/v1.0/myorg/groups/{0}/datasets/{1}/refreshes", res.GroupId, res.DatasetId));
//POST web request to create a datasource.
request.KeepAlive = true;
request.Method = "POST";
request.ContentLength = 0;
//Add token to the request header
request.Headers.Add("Authorization", String.Format("Bearer {0}", token));
Console.WriteLine("Dataset refresh request started for Dataset Id {0}", res.DatasetId);
//Write JSON byte[] into a Stream
using (Stream writer = request.GetRequestStream())
{
var response = (HttpWebResponse)request.GetResponse();
Console.WriteLine("Dataset refresh request done for Dataset Id {0}", res.DatasetId);
}
}