How can find the number of occurances of a particular substring in a string in C#?

You have to loop, using IndexOf to find the next instance... As best I know
there is no CountOf function - you have to write your own.

string in C#?

This is a little code which I wrote to solve my own problem.

Feel free to use this in case anybody needs it.

                public int GetSubstringCount( string passSubstring, string passString )
                {
                        int holdFound = 0;
                        for ( int i = 0; i < passString.Length ; i++ )
                        {
                                if ( passString.IndexOf( passSubstring, i ) > 0)
                                {
                                        i = i + passSubstring.Length;
                                        holdFound += 1;
                                }
                        }
                        return holdFound;
                }

Your routine had some odd properties - unless your needs were different from
just finding the number of distinct ocurrances of a substring in a string,
the following might work better...

public int CountDistinctIndexesOf(string substring, string value)
{
    int count = 0;
    int foundAtIndex;
    int searchFromIndex = 0;
    while((foundAtIndex = value.IndexOf(substring, searchFromIndex)) != -1)
    {
        searchFromIndex = foundAtIndex + substring.Length;
        count++;
    }
    return count;