The following snippet will demonstrate how to interact with http://tinypic.com, an image mirroring service, directly from a C# application, using the WebRobot component available from http://foxtrot-xray.com/web-robot/

void uploadTinyPic(string imagetags, string filename){
    foxtrot.xray.WebRobot wrobot = new foxtrot.xray.WebRobot();
    foxtrot.xray.Form wform;
    foxtrot.xray.Input wtags;
    foxtrot.xray.Input wimg;
    foxtrot.xray.Input wurl;
    wrobot.Base = "http://tinypic.com/";
    wrobot.LoadPage("/");
    wform = wrobot.Forms[0];
    wtags = wform.GetFieldByName("the_tag");
    wimg = wform.GetFieldByName("the_file");
    wtags.InputValue = imagetags;
    wimg.InputValue = filename;
    wrobot.SubmitForm(wform);
    wform = wrobot.Forms[0];
    wtags = wform.GetFieldByName("mytag");
    wimg = wform.GetFieldByName("myimg");
    wurl = wform.GetFieldByName("myurl");
    System.Windows.Forms.MessageBox.Show_
	("Image uploaded successfully!\r\n" +
	"HTML link: " + (string)wtags.InputValue + "\r\n" +
        "[IMG] tag: " + (string)wimg.InputValue + "\r\n" +
        "Image URL: " + (string)wurl.InputValue);
}

You can download a complete project illustrating its usage here, for more convenience.