新手上路，请教各位我为什么打不开SQL SERVER数据库呢(20分)

最后运行mycon.Open() 时报错
Dim strmycon As String = "server=localhost;user id=sa;password=;database=cis"
Dim strmycom As String = "select top 10 * from clients"
Dim mycon As New SqlClient.SqlConnection(strmycon)
Dim mycom As New SqlClient.SqlCommand(strmycom, mycon)
mycon.Open()