如何创建一个observablecollection类来在WPF应用程序中加载图像

I have developed a wpf application to load images in listbox.To load 300mb images it is taking time.I heard that to load images faster in listbox we have to use observablecollection,but i dont know how to use that one. Any suggestions plz.. Thanks in advanceI have developed a wpf application to load imag