asp.net - Performance of SqlParameter in C# -

i have stored procedure this:

create proc wsp_test (     @age           int     , @username    varchar(30) )     select    userid, username          users         username  '%' + @username + '%'     ,       age > @age 

and here c# code:

case 1:

sqlcommand _cmd = new sqlcommand(); _cmd.parameters.add("age", sqldbtype.int, 4); _cmd.parameters.add("username", sqldbtype.varchar, 30); 

case 2:

sqlcommand _cmd = new sqlcommand(); _cmd.parameters.add("age", sqldbtype.int); _cmd.parameters.add("username", sqldbtype.varchar); 

case 3:

sqlcommand _cmd = new sqlcommand(); _cmd.parameters.add("age"); _cmd.parameters.add("username"); 

case 4:

sqlcommand _cmd = new sqlcommand(); _cmd.commandtext = "exec wsp_test 20, 'john'"; 

now question has got performance specify parameter's datatype or length?

which 1 has best performance? there documents microsoft's web site can rely on?

or there security reasons specify parameter's datatype , length?

the performance of datatype irrelevant compared this:

where     username  '%' + @username + '%' 

this particular part of query going take exponentially more time dealing parameters.

i recommend don't care performance @ stage. it's early. not micro-benchmark of whether or not specify type , length of parameters. @ other factors. yes, should specify type, makes code more maintainable , can make runtime casting issues easier identify , solve.

if later determine particular code bottleneck application, using full text username field. can @ statistics code's usage , identify if need it. majority of queries match username or @ least starting with? use case search first on exact matches, faster, , search partial matches of no exact matches found?