In Asp.net, how does one check that the user name already exists?

A select statement is solved.
Select count (*) from user where userid = 'userid'

Then, let's make another judgment! If it is zero, this user name will not be available. If it is greater than zero, this user will be available!

Set rs = server. Createobject ("ADODB. recordset") 'to create a connection object
SQL = "select * from table name where user column name = '" & username & "'" 'T-SQL statement
Rs. Open SQL, Conn, 1, 3 'Open the database
If not Rs. EOF or not Rs. bof then 'judgment
Response. Write "User already exists" 'judgment result
End if 'exit judgment
Rs. Close 'Close the object
Set rs = nothing 'release Resources
Conn. Close 'Close object
Set conn = nothing 'release the resource