如何从JavaScript / C＃生成宽度CSS

I have been trying to get my C# variables values communicate with my HTML code through JavaScript the last couple of days, and now I have this HTML code which I would like to change through the value from C# upon page load. Upon page load I would like to set the css width value of the SPAN through JavaScript from my c# variable value. I have been trying to get my C# variables value