string fileName = "test.txt";
        string sourcePath = @"C:\Users\Public\TestFolder";
        string targetPath =  @"C:\Users\Public\TestFolder\SubDir";
        // Use Path class to manipulate file and directory paths.
        string sourceFile = System.IO.Path.Combine(sourcePath, fileName);
        string destFile = System.IO.Path.Combine(targetPath, fileName);