How do I join two paths in C#?

You have to use Path.Combine() as in the example below:

string basePath = @"c:\temp";
string filePath = "test.txt";
string combinedPath = Path.Combine(basePath, filePath); 
// produces c:\temp\test.txt

System.IO.Path.Combine() is what you need.

Path.Combine(path1, path2);