C# server form post

2015-10-15

1021
0
2015-10-19

C# server form post

以前用 form post的 Content-Type通常都是 "application/x-www-form-urlencoded"，今天才注意到用 server post "multipart/form-data"有些小細節；簡單的結論：

"application/x-www-form-urlencoded"：用鍵值對傳送純文字（key1=value1&ke2=value2）

"multipart/form-data;"：The content type "multipart/form-data" should be used for submitting forms that contain files, non-ASCII data, and binary data. 格式比較複雜，直接看 code XD（update: 2015-10-19 content type指定的 boundary要略過開頭的 "--"）

public enum ContentType
{
    Default, Multipart, JSON
}
public class Common
{
    public static string GetRemoteData(string url, ContentType contentType, System.Web.Mvc.FormCollection formData, string jsonData, string method = "POST")
    {
        HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);
        req.Method = method;
        req.Accept = "*/*";

        string postData = string.Empty;
        List dataList = new List();
        switch (contentType)
        {
            case ContentType.Multipart:
                // http://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.2
                string boundary = string.Format("--{0}", Guid.NewGuid());
                foreach (var key in formData.AllKeys)
                {
                    dataList.Add(boundary);
                    dataList.Add(string.Format("Content-Disposition: form-data; name=\"{0}\"", key));
                    dataList.Add(string.Empty);
                    dataList.Add(formData[key]);
                }
                dataList.Add(boundary + "--");
                postData = string.Join("\r\n", dataList);// "CR LF"
                req.ContentType = "multipart/form-data; boundary=" + boundary.Substring(2);
                break;
            case ContentType.JSON:
                postData = jsonData;
                req.ContentType = "application/json";
                break;
            case ContentType.Default:
            default:
                foreach (var key in formData.AllKeys)
                {
                    dataList.Add(string.Format("{0}={1}", key, formData[key]));
                }

                postData = string.Join("&", dataList);
                req.ContentType = "application/x-www-form-urlencoded";
                break;
        }

        string response = string.Empty;
        try
        {
            byte[] myData = Encoding.UTF8.GetBytes(postData);
            req.ContentLength = myData.Length;
            using (Stream streamOut = req.GetRequestStream())
            {
                streamOut.Write(myData, 0, myData.Length);
            }

            using (StreamReader streamIn = new StreamReader(req.GetResponse().GetResponseStream()))
            {
                response = streamIn.ReadToEnd();
            }
        }
        catch
        {
        }
        return response;
    }
}
// 使用： Common.GetRemoteData("http://localhost:49801/", ContentType.Default, formData: formData, jsonData: null);

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