How to fill forms and submit with Webclient in C#

How to fill forms and submit with Webclient in C#

多彩岁月 发布于 2021-11-27 字数 1050 浏览 1006 回复 6 原文

I'm new at using the the libraries WebClient, HttpResponse and HttpRequest in C#, so bear with me, if my question is confusing to read.

I need to build a WinForm based on C# which can open a URL, which is secured with the basic authorization. I did this with adding this to the header, like this:

using (WebClient wc = new WebClient())
    wc.Headers.Add(HttpRequestHeader.Authorization, "Basic " +
    Encoding.ASCII.GetBytes(username + ":" + password)));

So far, so good! Now I would like to fill a form with a number, and I find the source-code from the site, and discover that the name is "number". So I write this:

NameValueCollection formData = new NameValueCollection();  
formData["number"] = number
byte[] responseBytes = wc.UploadValues(theurl, "POST", formData);
string response = Encoding.ASCII.GetString(responseBytes);
textBox_HTML.Text = response; 

But how do I submit this? I will like to receive my "search-results"...

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喜你已久 2022-06-07 6 楼

You submitted it already with UploadValues. The question is: what is your "result-search"? What does the page return? HTML? If so - the HTML Agility Pack is the easiest way to parse html.

浅唱ヾ落雨殇 2022-06-07 5 楼

Posting a form with System.Net.Http.HttpClient and reading the response as string:

var formData = new Dictionary<string, string>();
formData.Add("number", number);

var content = new FormUrlEncodedContent(formData);

using (var httpClient = new HttpClient())
    var httpResponse = await httpClient.PostAsync(theurl, content);

    var responseString = await httpResponse.Content.ReadAsStringAsync();
任性一次 2022-06-07 4 楼

BFree's answer works great. One thing I would note, though, is that the data concatenation should really be url-encoded, otherwise you'd have trouble with things like "=" and "&" signs within the data.

The VB.NET version, urlencoded and with UTF-8 support, is below (note that url-encoding requires a reference to System.Web.dll, which only worked for me after I switched from .NET 4 Compact Framework to the regular .NET 4 Framework).

Imports System.Web
Imports System.Net
Imports System.IO

Public Class WebFormSubmitter

    Public Shared Function submit(ByVal address As String,
                                  ByVal values As Dictionary(Of String, String)) As String
        Dim encoding As New UTF8Encoding
        Dim postData As String = getPostData(values:=values)
        Dim data() As Byte = encoding.GetBytes(postData)

        Dim request = CType(WebRequest.Create(address), HttpWebRequest)
        request.Method = "POST"
        request.ContentType = "application/x-www-form-urlencoded"
        request.ContentLength = data.Length
        Dim newStream = request.GetRequestStream()
        newStream.Write(data, 0, data.Length)

        Dim response = request.GetResponse()
        Dim responseStream = response.GetResponseStream()
        Dim responseReader = New StreamReader(responseStream)
        Return responseReader.ReadToEnd()
    End Function

    Private Shared Function getPostData(ByVal values As Dictionary(Of String, String)) As String
        Dim postDataPairList As New List(Of String)
        For Each anEntry In values
            postDataPairList.Add(anEntry.Key & "=" & HttpUtility.UrlEncode(anEntry.Value))
        Return String.Join(separator:="&", values:=postDataPairList)
    End Function

End Class
和我恋爱吧 2022-06-07 3 楼

I have found a solution to my problem. First of all I was confused about some of the basics in http-communication. This was caused by a python-script i wrote, which have a different approach with the communication.

I solved it with generating the POST-data from scratch and open the uri, which was contained in the form-action.

↙厌世 2022-06-07 2 楼

Try this:

using System.Net;
using System.Collections.Specialized;  

NameValueCollection values = new NameValueCollection();
values.Add("TextBox1", "value1");
values.Add("TextBox2", "value2");
values.Add("TextBox3", "value3");
string Url = urlvalue.ToLower();

using (WebClient client = new WebClient())
    client.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
    byte[] result = client.UploadValues(Url, "POST", values);
    string ResultAuthTicket = System.Text.Encoding.UTF8.GetString(result);
转身泪倾城 2022-06-07 1 楼

You should probably be using HttpWebRequest for this. Here's a simple example:

var strId = UserId_TextBox.Text;
var strName = Name_TextBox.Text;

var encoding=new ASCIIEncoding();
var postData="userid="+strId;
postData += ("&username="+strName);
byte[]  data = encoding.GetBytes(postData);

var myRequest =
myRequest.Method = "POST";
myRequest.ContentLength = data.Length;
var newStream=myRequest.GetRequestStream();

var response = myRequest.GetResponse();
var responseStream = response.GetResponseStream();
var responseReader = new StreamReader(responseStream);
var result = responseReader.ReadToEnd();