HOW TO CODE FOR THE THIS STOREDPROCEDURE

Question

I GOT A STORED PROCEDURE FOR RETRIEVING DATA FROM FILTERED SEARCH.. A DROPDOWN WITH FIRSTNAME,LASTNAME AND  EMAIL AND A TEXTBOX WHICH FILTERS WITH EXACT SEARCH..

BELOW IS SP.. HOW TO CODE FOR THIS...

IF I CHOOSE FIRTSNAME FROM DDL AND ENTER FIRSTNAME IN TEXTBOX.. IT HAS TO FILTER AND BIND WITH EXACT DETAILS IN GRIDVIEW...SAME AS  FOR LASTNAME AND EMAIL...

Create Procedure [dbo].[spSearch]

( 

@firstName nvarchar(50) = null,

@lastName nvarchar(50) = null,

@email nvarchar(50) = null

) 

AS 

BEGIN

If @firstName is not null and Len(@firstName )=0 Set @firstName = null

If @lastName is not null and Len(@lastName )=0 Set @lastName = null

If @email is not null and Len(@email )=0 Set @email = null

Select 

*

From userinf

Where 

( @firstName is null or firstName Like @firstName )

and ( @lastName is null or lastName Like @lastName )

and ( @email is null or email Like @email )

END 

GO