在实体框架中排序和区分

Question

以下事件处理程序返回它的列表，但它不是不同的。列表中仍有许多重复。有什么想法吗？

Protected Sub ddlState_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ddlState.SelectedIndexChanged
    If IsPostBack Then
        ddlCity.Items.Clear()
        Dim context As New teckEntities()
        Using context
            'Dim query = From c In context.counties Where c.stateid = ddlState.SelectedValue Select c.countyname, c.id
            Dim query = From c In context.ziptaxes Where c.StateID = ddlState.SelectedValue Order By c.City Select c.City, c.ZipTaxId
            query.Distinct()
            ddlCity.DataSource = query.ToList()
            ddlCity.DataValueField = "ziptaxid"
            ddlCity.DataTextField = "City"
            ddlCity.DataBind()
        End Using
    End If

End Sub

Answer 1

应用distinct过滤器后，您应该分配查询的返回值。

 ddlCity.DataSource = query.Distinct().ToList()
 ddlCity.DataValueField = "ziptaxid"
 ddlCity.DataTextField = "City"
 ddlCity.DataBind()