在 RowDatabound vb.net GridView 中使用 DataBind 时出错

Question

请看下面的代码。我试图在 GridView 控件中编辑时填充下拉列表。

 Private Function GetSiteSelection() As DataTableReader

    ''' some code to return DataTableReader

End Function

Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs) Handles GridViewAttachedStation.RowDataBound

    If e.Row.RowType = DataControlRowType.DataRow Then

        Dim dtrSiteSel As Data.DataTableReader = Nothing

        If e.Row.RowState = DataControlRowState.Edit Then

            Dim SiteName As DropDownList = DirectCast(e.Row.FindControl("DropDownListType"), DropDownList)

            SiteName.DataSource = GetSiteSelection()
            SiteName.DataTextField = "CODE_NAME"
            SiteName.DataValueField = "CODE_ID"
            SiteName.DataBind() <-- Error is here

        End If

    End If
End Sub

在 SiteName.DataBind()

处出现错误

Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control.

根据要求设计模型：这适用于简单的文本框，但不适用于下拉菜单。我参考了其他来源，但大多数都使用相同的方式 - 这是行不通的。

<asp:GridView ID="GridView1"
            runat="server"
            AutoGenerateColumns="False"
            Width="100%"
            CellPadding="0"
            BorderStyle="None"
            AllowSorting="true"
            OnRowEditing="OnRowEditing">
            <AlternatingRowStyle CssClass="tblAtlData"></AlternatingRowStyle>
            <RowStyle ForeColor="Black" CssClass="tblData"></RowStyle>
            <FooterStyle CssClass="tblHeader"></FooterStyle>
            <PagerStyle Font-Bold="True" HorizontalAlign="Left" ForeColor="BlueViolet" CssClass="tblData"></PagerStyle>
            <HeaderStyle CssClass="tblHeader" ForeColor="White"></HeaderStyle>
            <Columns>

                <asp:TemplateField HeaderText="EDIT">
                    <ItemTemplate>
                        <asp:LinkButton ID="EditLinkButton" Text="Edit" Font-Bold="true" CommandName="Edit" runat="server"
                            CommandArgument='<%# Eval("STATION ID") %>' />
                    </ItemTemplate>
                    <ItemStyle HorizontalAlign="Center" />
                    <HeaderStyle Width="5%" />
                    <EditItemTemplate>
                        <asp:LinkButton ID="UpdateLinkButton" Text="Update" Font-Bold="true" CommandName="Update" runat="server"
                            CommandArgument='<%# Eval("STATION ID") %>' />
                        <asp:LinkButton ID="CancelLinkButton" Text="Cancel" Font-Bold="true" runat="server"  OnClick="OnCancel" />

                    </EditItemTemplate>
                </asp:TemplateField>

                <asp:TemplateField HeaderText="Site Selection Type">
                    <ItemTemplate>
                        <asp:Label ID="lblSiteSelection" runat="server" Text='<%# Eval("Site") %>' />
                    </ItemTemplate>
                    <ItemStyle Width="10%" CssClass="GeneralText" />
                    <HeaderStyle Width="10%" /> 
                    <EditItemTemplate>
                      <asp:DropDownList runat="server" ID="DropDownListTypeNameRow" CssClass="GeneralText"
                        onkeydown="typeAhead()" AutoPostBack="true" DataTextField='<%# Eval("SiteSelectionType") %>' />
                    </EditItemTemplate>
                </asp:TemplateField>

            </Columns>
        </asp:GridView>

Answer 1

该错误表明您试图在不支持数据绑定的属性中使用 DataBinder.Eval 方法。

这个 DropDownList 设置应该可以解决问题：

<asp:DropDownList runat="server" ID="DropDownListTypeNameRow" CssClass="GeneralText"
                  onkeydown="typeAhead()" AutoPostBack="true"
                  DataTextField="CODE_NAME" DataValueField="CODE_ID"
                  SelectedValue='<%# Eval("SiteSelectionType") %>' />

由于 DataTextField 属性已在代码隐藏中设置为 column/field 名称，您还应将其设置到具有相同名称的标记中，即 CODE_NAME.

如果您想在相应行的每个下拉列表中显示默认选择值，Eval 部分应该放在 SelectedValue 属性中。

Answer 2

ASP.Net TemplateField 的 ItemTemplate 中带有 DropDownList 的 GridView。

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
    <Columns>
        <asp:BoundField HeaderText="Name" DataField="ContactName" />
        <asp:TemplateField HeaderText = "Country">
            <ItemTemplate>
                <asp:Label ID="lblCountry" runat="server" Text='<%# Eval("Country") %>' Visible = "false" />
                <asp:DropDownList ID="ddlCountries" runat="server">
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>


Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not IsPostBack Then
        GridView1.DataSource = GetData("SELECT ContactName, Country FROM Customers")
        GridView1.DataBind()
    End If
End Sub

Private Function GetData(query As String) As DataSet
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Dim cmd As New SqlCommand(query)
    Using con As New SqlConnection(conString)
        Using sda As New SqlDataAdapter()
            cmd.Connection = con
            sda.SelectCommand = cmd
            Using ds As New DataSet()
                sda.Fill(ds)
                Return ds
            End Using
        End Using
    End Using
End Function

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If (e.Row.RowType = DataControlRowType.DataRow) Then

       'Find the DropDownList in the Row.
        Dim ddlCountries As DropDownList = CType(e.Row.FindControl("ddlCountries"), DropDownList)
        ddlCountries.DataSource = GetData("SELECT DISTINCT Country FROM Customers")
        ddlCountries.DataTextField = "Country"
        ddlCountries.DataValueField = "Country"
        ddlCountries.DataBind()

        'Add Default Item in the DropDownList.
        ddlCountries.Items.Insert(0, New ListItem("Please select"))

        'Select the Country of Customer in DropDownList.
        Dim country As String = CType(e.Row.FindControl("lblCountry"), Label).Text
        ddlCountries.Items.FindByValue(country).Selected = True
    End If
End Sub

Answer 3

只删除条件

If e.Row.RowState = DataControlRowState.Edit Then

在 RowDatabound vb.net GridView 中使用 DataBind 时出错

Error while using DataBind in RowDatabound vb.net GridView

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