public static string Combine(
    string path1,
    string path2
)

Example:

public class CombineMethod {

    public static void Main() {

        string path1 = "c:\\temp";
        string path2 = "subdir\\file.txt";
        string path3 = "c:\\temp.txt";
         
        string combination = Path.Combine(path1,path2);    
        //  combination variable  will contain path like that c:\temp\subdir\file.txt
        string combination1    =Path.Combine(path1,path3); 

          // combination1 variable will contain path like that c:\temp\file.txt

         }
            }