what is the use of indexof ,CInt method in vb.net?

IndexOf is used to locate an object within another object. If you have a string and want to find a letter within that string you can go.

String myString = "abc";
int i = myString.IndexOf("a");
in this case i is 1. the function will return -1 if the string is not found. You can also use IndexOf on Collections.

Cint is used to convert to an Integer Data Type.
String num = "1";
int intNum = Cint(num);