Position of a string

Question

 

//Write a program in C# Sharp to search the position of a substring within a string. Not able to get the output and proceed further.... pls help

string sentence = Console.ReadLine();

foreach (string item in sentence)

{

Console.WriteLine(item);

}

int pos = 1;

Console.WriteLine("Enter the substring");

string substring = Console.ReadLine();

char[] substringchar = substring.ToCharArray();