How to find substring from string without using indexof method in C#?

Question

I want to find the position of a substring in a string if present without using any string method including indexof. I tried so much times but failed. Will anybody tell me h

Answer 1

public static findindex(String str,String substr)
 {
     char a[]=str.toCharArray();
     char b[]=substr.toCharArray();
     int j=0,t=0;
     for(int i=0;i<str.length()&&j<substr.length();i++)
       {
       if(a[i]==b[j])
          {
            t=i;
            j++;
          }
       else
       continue;
       }
      if(t==0)
      return -1;
      else
      return t-substr.length()+1;
      }//in java