Checking Null Value In VB Script

Dear All ,
I have a problem when reading from the SQLServer Database, when there is null value found.  please help me by correcting the below script:
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( Imported , Dimed SQLCOnnection , Dimed SQLCommand , datareader as well)
Dim sql As String = "select count(*) from usr_request where pending_status='P' and request_by='" & Me.lblp_user.Text & "'"    
         Try               con.Open()                 cmd = New SqlCommand(sql, con)                 _dr = cmd.ExecuteReader                 If dr(0) is DBNull.Value Then< ...