无法找到表 0。 谁来帮帮我~

myconn = New SqlConnection("server=localhost;database=database;uid=sa;pwd=sa")
  myadapter = New SqlDataAdapter(sqlstr, myconn)
  ds = New DataSet
  myadapter.Fill(ds)

 Dim sqlstr As String
  Dim ds As DataSet
  ds = New DataSet
  If pwdstr = "" Then
  sqlstr = "select * from register where id='" + userstr.Trim + "' and rkey is null"
  Else
  sqlstr = "select * from register where id='" + userstr.Trim + "' and rkey='" + pwdstr + "'"
  End If
  fill(sqlstr)
  If ds.Tables(0).Rows.Count = 0 Then
  close()
  Return -1
  End If
  ds.Clear()
  close()
  Return 1

myconn.Open()了木有