请大神看看这串代码有问题吗？为什么调试下拉列表中没有数据

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
Dim conn As String
conn = "provider=microsoft.ace.oledb.12.0;data source=D:\LIANXI\Database1.mdb;Persist Security Info=False"
Dim myconn As New OleDb.OleDbConnection(conn)
Dim myselectquery As String = "select *from yuanzhu "
myconn.Open()
Dim cmd As New OleDb.OleDbCommand(myselectquery, myconn)
Dim myreader As OleDb.OleDbDataReader = cmd.ExecuteReader
myreader.Read()
ComboBox1.Items.Add(myreader(0))
myconn.Close()
End Sub