The IndexOf method in String Class returns the index of the first occurrence of the specified substring.
System.String.IndexOf(String str) As Integer
Parameters:
str - The parameter string to check its occurrences
Returns:
Integer - If the parameter String occurred as a substring in the specified String
it returns position of the first character of the substring .
If it does not occur as a substring, -1 is returned.
Exceptions:
System.ArgumentNullException: If the Argument is null.
For ex:
"This is a test".IndexOf("Test") returns 10
"This is a test".IndexOf("vb") returns -1
VB.NET SourceCode
When you execute this program you will get the number 14 in the message box. That means the substring "BOOKS" occurred and start in the position 14.