What do you mean by first all character from string? if you want first char from string than simply get substring as
string str = "This is the complete sentance";
char c = str.Substring(0,1); // it return first char "T" from string to assign c
Output is
T
//But if you want to get all first character from each word in string than try this
string[] wordsFirstChar = str.Split(' ');
foreach (string word in wordsFirstChar )
{
Console.WriteLine(word.Substring(0,1));
}
here you will get output first all character in sequance as folllows
Output is
T
i
t
c
s