"Select Count (*) from FILENAME where fieldname = '" & Trim(textbox.text) & "' "

if count = 0 then
' do something
end if

Dim myReader As SqlDataReader
conn = GetConnect()
conn.Open()
Dim temp As String
    Try
    Dim sql As String = "Select Count (*) AS 'KODE' from FILENAME where fieldname = '" & Trim(textbox.text) & "'"
    Dim comm As SqlCommand = New SqlCommand(sql, conn)
    myReader = comm.ExecuteReader
    If myReader.HasRows Then
        While myReader.Read()
            temp = myReader.Item("KODE")
        End While
	End If
		myReader.Close()
    Catch ex As Exception
    End Try
    conn.Close()
 
    If temp = 0 then
        'Do Something
    End If