System.Net.WebClient

Provides a simple, programmable interface to transmit data using the HTTP, FTP, and file protocols. This class is useful for applications that need to send and receive data from a resource over a network.

Properties

BaseAddress

string BaseAddress { get; set; }

Gets or sets the base address of URIs used in requests made by this WebClient. This property can be used to simplify requests to a specific server.

Credentials

ICredentials Credentials { get; set; }

Gets or sets the credentials used to authenticate the request to the server. This is useful for accessing resources that require authentication.

Headers

WebHeaderCollection Headers { get; }

Gets the collection of HTTP headers associated with the request. You can use this property to add custom headers or modify existing ones.

Methods

DownloadString

string DownloadString(string address)

Downloads the resource with the specified URI to a string.

Parameters

address: The URI of the resource to download.

Returns

A string containing the resource.

UploadString

string UploadString(string address, string data)

Uploads the specified string to the specified resource.

Parameters

address: The URI of the resource to upload to.
data: The string to upload.

Returns

A string containing the response from the server.

DownloadFile

void DownloadFile(string address, string fileName)

Downloads the resource with the specified URI to a local file.

Parameters

address: The URI of the resource to download.
fileName: The name of the local file to store the downloaded content.

UploadFile

byte[] UploadFile(string address, string method, string fileName)

Uploads a local file to a resource specified by a URI.

Parameters

address: The URI of the resource to upload to.
method: The HTTP method to use for the upload (e.g., "POST").
fileName: The path to the local file to upload.

Returns

A byte array containing the response from the server.

Events

DownloadProgressChanged

event DownloadProgressChangedEventHandler DownloadProgressChanged

Occurs when progress is made during an asynchronous download operation.

UploadProgressChanged

event UploadProgressChangedEventHandler UploadProgressChanged

Occurs when progress is made during an asynchronous upload operation.

C# Example: Downloading a Web Page


using System;
using System.Net;

public class Example
{
    public static void Main(string[] args)
    {
        using (WebClient client = new WebClient())
        {
            try
            {
                string url = "https://www.example.com";
                Console.WriteLine($"Downloading content from: {url}");
                
                string html = client.DownloadString(url);
                
                Console.WriteLine("Download complete. Content length: " + html.Length);
                // You can further process the 'html' string here.
                // For brevity, we won't print the entire HTML.
                Console.WriteLine("First 100 characters: " + html.Substring(0, Math.Min(100, html.Length)));
            }
            catch (WebException e)
            {
                Console.WriteLine($"An error occurred: {e.Message}");
            }
        }
    }
}

C# Example: Uploading a File


using System;
using System.Net;
using System.IO;

public class FileUploader
{
    public static void Main(string[] args)
    {
        string url = "https://httpbin.org/post"; // A service that echoes POST data
        string filePath = "my_document.txt";
        string contentToUpload = "This is the content of my file.";

        // Create a dummy file for demonstration
        File.WriteAllText(filePath, contentToUpload);
        Console.WriteLine($"Created temporary file: {filePath}");

        using (WebClient client = new WebClient())
        {
            try
            {
                Console.WriteLine($"Uploading {filePath} to {url}");
                // The method "POST" is common for uploads.
                byte[] responseBytes = client.UploadFile(url, "POST", filePath);
                string responseString = System.Text.Encoding.UTF8.GetString(responseBytes);
                
                Console.WriteLine("Upload successful. Server response:");
                Console.WriteLine(responseString);
            }
            catch (WebException e)
            {
                Console.WriteLine($"An error occurred during upload: {e.Message}");
            }
            finally
            {
                // Clean up the dummy file
                if (File.Exists(filePath))
                {
                    File.Delete(filePath);
                    Console.WriteLine($"Deleted temporary file: {filePath}");
                }
            }
        }
    }
}