underscore surrounded by backslashes

Question

I am trying to concatenate some file name constituents to make sure if I already have an identically-named file, the new one gets a new name with an underscore and an incremental counter.

I have written the following which I believe should work:

string tempPath = Path.Combine(Application.dataPath, "MyValues");
tempPath = Path.Combine(tempPath, "_");
tempPath = Path.Combine(tempPath, counter.ToString() + ".csv");

After I noticed no file is actually saved, I included Debug.Log(tempPath) to see what it returns, and surprisingly I get the following:

MyUnityProject/Assets\MyValues\_\0.csv

Firstly, why are there \ instead of /?

Also, where are the backslashes surrounding the underscore coming from?

Finally, instead of manually removing them, how could I get the correct syntax back? For example MyValues_0.csv, MyValues_1.csv, etc...

Answer 1

By looking at the source code for the Path class available here: https://referencesource.microsoft.com/#mscorlib/system/io/path.cs,16ed6da326ce4745

We can see that the method Combine calls the method CombineNoChecks for each pair of string paths and returns the following:

return path1 + DirectorySeparatorCharAsString + path2;

The value of DirectorySeparatorCharAsString is:

internal const string DirectorySeparatorCharAsString = "\\";

There are also other separators defined in the class so you get the right one according your running platform:

// Platform specific alternate directory separator character.  
// This is backslash ('\') on Unix, and slash ('/') on Windows 
// and MacOS.
public static readonly char AltDirectorySeparatorChar = '/';

So I wouldn't worry about what the method is returning, it should just work.

Answer 2

Whether \ or / is used to build a valid path is the whole reason why you even use Path.Combine at all:

• It uses whatever the current Plattform/OS understands to combine two strings to a path and thereby makes it plattforms independent.
• It also adds some additional checks if the provided strings are valid path snippets and thereby makes it also saver to use than a simple concatenation.

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What you do

string tempPath = Path.Combine(Application.dataPath, "MyValues");
tempPath = Path.Combine(tempPath, "_");
tempPath = Path.Combine(tempPath, counter.ToString() + ".csv");

Is assuming that MyValue and _ are folder names.

Use Path.Combine only for combining folders and the final filename not for concatenating the filename itself.

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What you want to do instead is building the complete filename by string concatenation e.g. using string.Format

string filename = string.Format("MyValues_{0}.csv", counter.ToString());

or also $ (string interpolation)

string filename = $"MyValues_{counter.ToString()}.csv";

which are just esier ways of writing

string filename = "MyValues_" + counter.ToString() + ".csv";

and than use Path.Combine only to combine the complete filename with the given system folder path like

string tempPath = Path.Combine(Application.dataPath, filename);