When it comes to choosing between ViewState and Caching it
all comes down to what you are doing. ViewState is an ideal
candidate if you are planning to save small values. Mostly
values of server controls are saved in ViewState. If you
plan to store large datasets, datatables or collections than
data caching is an excellent candidate.

If you want to store large datasets and datatables than
data caching is an good option and for small values you 
should use viewstate.

As a part of Visual Studio Tool there is a tool named
Dotfuscator, using which we can remake the dll such that the
internal code is not visible.

we have Inproc server and outproc server
for storing session in different server we have to specify 
in the webcofing mode="state" and state mode session to be 
srialized. and it stores in aspnet_state.exe

If we specify mode ="Inproc"  session will store in 
webserver itself under aspnet_wp.exe
If we specify mode = "Sqlserver" session will store in 
sqlserver and it has to be serialized.

No,

yes you can

private void RegExp(string input)
{
	string s = input;
	Regex regexp = new Regex("^[0-9]*_[A-Za-z]*$");	
	if(regexp.IsMatch(input))
		Console.WriteLine("Matched");
	else
		Console.WriteLine("Not Match");
}

val(textbox1.text)+val(textbox2.text)=txtbox3.text

IN,OUT,INOUT are the valid parameter types that we can pass
in a Indexer

here 
executescalar()
executereader()
executenonquery()
these comes with Begin and End
like Beginexecutescalr()
     Endexecutescalar()
       .......
  by using these command we can achieve asynch comm in 
ado.net