从C＃中的最后一个对象开始循环

Question

How can I loops the list of object strating from last position object in c#. Here, I have asp.net mvc 3 application where I need to create the directory to upload the path according to the category available if directory is not available. But list of category object are in opposite order where child category is at first position. I want to create the folder of child category inside the parent category. so I want to start the loops in reverse order or is there any function to reverse the list of category object. I have following foreach loops:

    foreach (var item in parentcategory)
    {   
        categorypath += item.CategoryName + "/" ;
    }

any helps is greatly appreciated

Answer 1

Simpliest solution, but not most efficient is:

parentcategory.Reverse();
foreach (var item in parentcategory)
{   
    categorypath += item.CategoryName + "/" ;
}

or:

for (int i=parentcategory.Count-1; i>=0; i--)
{   
    var item = parentcategory[i];
    categorypath += item.CategoryName + "/" ;
}

Answer 2

You actually don't have to loop in reverse.

foreach (var item in parentcategory)
{   
    categorypath = item.CategoryName + "/" + categorypath;
}

Not terribly efficient but it works.

You could also consider using System.IO.Path.

var categorypath = Path.Combine(categories.Reverse().ToArray());

Answer 3

Instead of appending to the string, you could also prepend:

foreach (var item in parentcategory)
    {   
        categorypath = item.CategoryName + "/" + categorypath;
    }

Note that in all solutions presented so far, the resulting string has a trailing "/".