Работа со строками в C#

string a = "Some text";
ConsoleWriteLine(a.Lenght);
//9

ConsoleWriteLine(a.IndexOf('t'));
//5

a = a.Insert(0, "This is ");
ConsoleWriteLine(a);
//This is Some text

a = a.Replace("This is", "I am");
ConsoleWriteLine(a);
//I am Some text

if(a.Contains("some"))
  ConsoleWriteLine("found");
//found

a = a.Remove(4);
ConsoleWriteLine(a);
//I am

a = a.Substring(2);
ConsoleWriteLine(a);
//am