Int32.Parse(Regex.Match(some_string, @"d+").Value);

public string GetFirstNumber(string some_string) {

   if (string.IsNullOrEmpty(some_string)) {
        return string.Empty; // You could return null to indicate no data
   }

    StringBuilder sb = new StringBuilder();
    bool found = false;

    foreach(char c in some_string){
        if(Char.IsDigit(c)){
            sb.Append(c);
            found = true;
        } else if(found){
            // If we have already found a digit,
            // and current character is not a digit, stop looping
            break;
        }
    }

    return sb.ToString();
}

string str = "768 - Hello World";
int i = Int32.Parse(str.Split(' ').First());

public int GetLeadingIntegerFromString(string myString)
{
    if (string.IsNullOrWhiteSpace(myString))
        return;

    var parts = myString.Split('-');
    if (parts.Length < 1)
        return;

    var number = int.Parse(parts[0].Trim());

    return number;
}