how to count the words in string with out using built in functions in c#

can u take string is a user entre and use this

string str=textbox1.text;

int i=myOwnGetStringLength(str);

scriptmanager.startupscript(this,this.gettype(),"script","alert("+i+")",true); 

int myOwnGetStringLength(String str)
{
    int count = 0;
    foreach(Char c in str)
        count++;
    return count;
}

in built in funtion

 
string str=textbox1.text; 

int i=str.length;

 scriptmanager.startupscript(this,this.gettype(),"script","alert("+i+")",true);