ASP.NET Core Download File From URL/URI Using WebClient

This article uses ASP.NET Core. If using the older .NET Framework, see this article, though, not much has changed.

Using WebClient.DownloadFile() is a very efficient way to download a file and save it somewhere to be processed. Notice that a cookie is being sent to the server.

using (System.Net.WebClient wc = new System.Net.WebClient())
{
	wc.Headers.Add("Cookie: Authentication=user"); // add a cookie header to the request
	try
	{
		string filename = System.Guid.NewGuid().ToString("N"); // use global unique identifier for file name to avoid conflicts
		wc.DownloadFile("http://www.prowaretech.com/", "C:\\files\\" + filename); // could add file extension here
		// do something with file
	}
	catch (System.Exception ex)
	{
		// check exception object for the error
	}
}

WebClient.DownloadString() is a less efficient use of server memory.

using (System.Net.WebClient wc = new System.Net.WebClient())
{
	try
	{
		string str = wc.DownloadString("http://www.prowaretech.com/");
		// do something with str
	}
	catch (System.Exception ex)
	{
		// check exception object for the error
	}
}

WebClient.DownloadData() is another less efficient use of server memory. It downloads a file into a byte array.

using (System.Net.WebClient wc = new System.Net.WebClient())
{
	try
	{
		byte[] data = wc.DownloadData("http://www.prowaretech.com/");
		// do something  with data
	}
	catch (System.Exception ex)
	{
		// check exception object for the error
	}
}

WebClient.OpenRead() is a less efficient use of server memory if reading the whole stream into memory. Use StreamReader.Read() to be conservative with memory particularly if working with large files on a server.

using (System.Net.WebClient wc = new System.Net.WebClient())
{
	try
	{
		using (System.IO.Stream stream = wc.OpenRead("http://www.prowaretech.com/"))
		{
			using (System.IO.StreamReader reader = new System.IO.StreamReader(stream))
			{
				string str = reader.ReadToEnd(); // could read one character at a time with reader.Read() which is more efficient with regard to memory usage
				// do something with str
			}
		}
	}
	catch (System.Exception ex)
	{
		// check exception object for the error
	}
}