I know there are lot of question which is asked previously about 

> 
> The variable which is assigned but its value is never used
> 
> 
> 

[Here](https://stackoverflow.com/questions/30658839/variable-is-assigned-but-its-value-is-never-used-c),[Here](https://stackoverflow.com/questions/6330491/weird-warning-is-assigned-but-its-value-is-never-used) and [Here](https://stackoverflow.com/questions/35324313/c-sharp-warning-the-variable-is-assigned-but-its-value-is-never-used)

I am getting compile time Error instead of warning which causes compile or rebuild to fail.
i didn't update my Visual studio 2015 nor do i installed any VS extension 

so my question is what can i do so Visual studio show `warning` instead of Compile time Error.

[![enter image description here](https://i.stack.imgur.com/aI7Dj.png)](https://i.stack.imgur.com/aI7Dj.png)