Starting with C# 6.0, this is possible:
using static FileHelper;
// in a member
ExtractSimpleFileName(file)
However, previous versions of C# do not have static imports.
You can get close with an alias for the type.
using FH = namespace.FileHelper;
// in a member
FH.ExtractSimpleFileName(file)
Alternatively, change the static method to an extension method on the type – you would then be able to call it as:
var value = file.ExtractSimpleFileName();