主题：[求助]生成树项目代码出错

Dim trv As WinForm.TreeView = e.Form.Controls("TreeView1")
Dim dic As new Dictionary(Of String,Winform.TreeNode)
Dim nd As WinForm.TreeNode
Dim pd As WinForm.TreeNode
Dim cmd As New SQLCommand
Dim drs As DataTable
cmd.CommandText = "SELECT DISTINCT 编码,名称,上级编码 From {组织机构}"
drs = cmd.ExecuteReader
For Each dr As DataRow In drs
    If dr.IsNull("上级编码") = False Then
        If dic.ContainsKey(dr("上级编码")) Then
            pd = dic(dr("上级编码"))
            nd = pd.Nodes.add(dr("编码"),dr("编码")+dr("名称"))
            dic.add(dr("编码"),nd)
        End If
    Else
        nd = trv.Nodes.add(dr("编码"),dr("名称"))
        dic.add(dr("编码"),nd)
    End If
    If dr("分支机构") = True
        nd.BackColor= color.Gainsboro
        nd.ForeColor = color.white
    End If
Next

保存代码下出现如下提示：

编译错误：expression is of type 'datatable',which is not a collection type.

错误代码：for each dr as datarow in drs

请各位大师帮看看,是怎么回事呀?