Is it effective to use get; set; to avoid redundant processes?

Question

I wanted to avoid running the code HttpContext.Current.Server.MapPath every time file_path_includes is called.

Is the below an effective way of doing so?

private static string file_path_includes_;
public static string file_path_includes
{
    get
    {
        if (file_path_includes_ == null)
            file_path_includes_ = HttpContext.Current.Server.MapPath("/_includes") + @"\";
        return file_path_includes_;
    }
}

So the better implentation would be a static constructor as such:

public static string file_path_includes;

static ParentClassName()
{
    file_path_includes = HttpContext.Current.Server.MapPath("/_includes") + @"\";
}

Answer 1

Is it best to initialize a static member once, in a static constructor. If that is not possible, then a lazy initialization can be done like this. (Similar code to yours, just using the null coalescing operator.)

private static string file_path_includes_;

public static string file_path_includes
{
    get
    {
        return 
            file_path_includes_ ??
                (file_path_includes_ = HttpContext.Current.Server.MapPath("/_includes") + @"\");
    }
}

Answer 2

Since the file_path_includes remains the same so it makes sense to make it readonly. Instead of using a static constructor you can initalize it inline as it will make loading the variable even lazier.

private static readonly string file_path_includes = HttpContext.Current.Server.MapPath("/_includes") + @"\";

As Magus mentioned variable naming convention needs some thought.