how to use indexof in c# code example

Example 1: c sharp index of substring

// To find the index of the first substring in a string use
// 'IndexOf()'
string str = "Hello World!"
str.IndexOf("o"); // Output: 4

// You can give a starting index and a length to search at
str.IndexOf("o", 6, 4); // Output: 7

// To find the last instance of a substring use 'LastIndexOf()'
str.LastIndexOf("o"); // Output: 7

Example 2: c# IndexOf

string word = "Hello";
int where = word.IndexOf("e");
// int where returns index number where the letter "e" is located.
// --0-1-2-3-4-- < Index number
// --H-e-l-l-o-- < Word
// In this case, the letter "e" is located in the index number 1

Example 3: indexof c#

string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+---";
string br2 = "012345678901234567890123456789012345678901234567890123456789012345678";
string str = "Now is the time for all good men to come to the aid of their country.";
int start;
int at;
int end;
int count;

end = str.Length;
start = end/2;
Console.WriteLine();
Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, end-1);
Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
Console.Write("The string 'he' occurs at position(s): ");

count = 0;
at = 0;
while((start <= end) && (at > -1))
{
    // start+count must be a position within -str-.
    count = end - start;
    at = str.IndexOf("he", start, count);
    if (at == -1) break;
    Console.Write("{0} ", at);
    start = at+1;
}
Console.WriteLine();

/*
This example produces the following results:

All occurrences of 'he' from position 34 to 68.
0----+----1----+----2----+----3----+----4----+----5----+----6----+---
012345678901234567890123456789012345678901234567890123456789012345678
Now is the time for all good men to come to the aid of their country.

The string 'he' occurs at position(s): 45 56

*/