1.絕對路徑
this.pictureBox2.Image=Image.FromFile("E://001.jpg"); 

2.相對路徑:
Application.StartupPath;  
可以得到程序根目錄  
this.pictureBox2.Image=Image.FromFile(Application.StartupPath "//1.gif"); 

3.獲得網絡圖片的路徑
this.pictureBox2.Image= Image.FromStream(System.Net.WebRequest.Create(http://www.companysz.com/images/logo.gif).GetResponse().GetResponseStream());