c# Convert curl request into http request?

Question

Reference:

curl https://api.lob.com/v1/postcards \

-u test_0dc8d51e0acffcb1880e0f19c79b2f5b0cc: \

-d "description=Demo Postcard job" \

-d "to[name]=Harry Zhang" \

-d "to[address_line1]=185 Berry St" \

-d "to[address_line2]=# 6100" \

-d "to[address_city]=San Francisco" \

-d "to[address_state]=CA" \

-d "to[address_zip]=94107" \

-d "to[address_country]=US" \

-d "from[name]=Leore Avidar" \

-d "from[address_line1]=185 Berry St" \

-d "from[address_line2]=# 6100" \

-d "from[address_city]=San Francisco" \

-d "from[address_state]=CA" \

-d "from[address_zip]=94107" \

-d "from[address_country]=US" \

-d "front=tmpl_b846a20859ae11a" \

-d "back=tmpl_01b0d396a10c268" \

-d "merge_variables[name]=Harry"

im trying convert the above CURL into C# HTTPRequest

WebRequest req = WebRequest.Create(@"https://api.lob.com/v1/postcards?description=Demo Postcard job&to[name]=Harry Zhang&to[address_line1]=185 Berry St&to[address_line2]=no 6100&to[address_city]=San Francisco&to[address_state]=CA&to[address_zip]=94107&to[address_country]=US&from[name]=Leore Avidar&from[address_line1]=185 Berry St&from[address_line2]=no 6100&from[address_city=San Francisco&from[address_state]=CA&from[address_zip]=94107&from[address_country]=US&front=tmpl_a5bb07d8301c90e&back=tmpl_efeba684a3e3c3b&merge_variables[name]=saravanan");

//WebRequest req = WebRequest.Create(@"https://api.lob.com/v1/addresses/adr_58f75c708b98d2fc");

req.Method = "POST";

req.Headers["Authorization"] = "Basic " + Convert.ToBase64String(Encoding.Default.GetBytes("test_48d2bbf75401d119bfae5526:"));

HttpWebResponse resp = req.GetResponse() as HttpWebResponse;

Stream zStream;

StreamReader zStreamReader;

string zszReturn = "";

zStream = resp.GetResponseStream();

zStreamReader = new StreamReader(zStream, Encoding.UTF8);

zszReturn = zStreamReader.ReadToEnd();

but it throws 422 exception... i dont wheather the url which i passing is in correct formate or not..