CSOM +Sandbox+SPO Problem!

Hello All,

I’m facing problem during my project simple task.

Here is my requirement-

I’m creating a Sandbox solution for SPO(uploading WSP).In that solution. I’m writing code to fetch data from list and bind my data to ListView(Control).But it is not working.I don’t know why but if I write code just to simply get my Web title in Sandbox solution using CSOM(managed code) it is not working fine.

And always display error of Full Trust.

I need your attention to this.

Please suggest me something!

Thanks!☺