access a file on the server in ASP.NET MVC

Question

In my ASP.NET MVC application I am generating excel reports, I have a template file that I copy and alter. This template file is put in a folder in my solution. I want to use it as follows:

string templatePath = @"\Templates\report.xlsx";

using (var template = File.OpenRead(templatePath)) {
  // Copy template and process content
}

But This code generates an exception

 Couldnot find a part of the path 'C:\Templates\report.xlsx'.

How should I reference this file?

I also tried using

string templatePath = @"~\Templates\report.xlsx";

But that results in

Could not find a part of the path 'C:\Program Files\Common Files\Microsoft Shared\DevServer\10.0\~\Templates\report.xlsx'.

It does work however when I use the absolute path but that is meaningless to my production server.

Solution

I believe you would do it the normal ASP.NET way, assuming Templates is a directory in your web application.

string templatePath = @"~\Templates\report.xlsx";

using (var template = File.OpenRead(Server.MapPath(templatePath))) {
  // Copy template and process content
}

Comments

[Janvi Patel]

If you use the tilde in the path it is important you call Server.MapPath on the string to resolve it.

[Charlino]

What about trying it this way Server.MapPath("/Templates/report.xlsx") ... ? Hang on... you just deleted your comment saying it didn't work. Did it?

[Jan]

I didn't read his answer very well at first. He has put it inside of the File.OpenRead(). Putting that statement on the assignment is cleaner code in my opinion but that's personal flavor.

[Jan]

backslashes work for me, can you explain why forward slashes are better?

[Chev]

Guess I've never tried it with back slashes. Back slashes usually represent an actual physical path while forward slashes represent the virtual directory that houses your application. Server.MapPath() takes a virtual directory on the same server and maps it to it's fully qualified physical path. Maybe it's smart enough to know what you are intending to do and that's why backslashes work. I'm not entirely sure.

[Chev]

I bet I know why it works. Templates\report.xlsx is a physical subdirectory of your root virtual directory so it's working. However, I bet if the Templates directory was only a virtual subdirectory of your root virtual directory and that the physical directory was somewhere else then backslashes would not work. I should test this out sometime. If that's the case then I would still recommend forward slashes just in case you ever need to move your directory structure around while leaving your virtual directories the same..