动态 GridView 下拉列表

Question

我有一个包含以下字段的网格视图：

讲座 ID、讲师姓名、主题，网格视图包含用于插入、编辑和删除的链接按钮。我的内容 需要的是，当我单击时，编辑主题列应包含下拉列表以选择主题。 如果 GridView 行未处于 EDIT 模式或 INSERT 模式，则不应显示 DROPDOWN，而仅显示讲师教授的主题。

Answer 1

这可以通过将 SUBJECT 列设置为 TemplateField 来完成，如下所示：

<asp:TemplateField Header="Subject">
                    <EditItemTemplate>
                        <asp:DropDownList ID="subjectDDl" runat="server"></asp:DropDownList>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="subjectLabel" runat="server"></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>

您可能已经添加了 ButtonField 列来调用 EDIT、INSERT 和 DELETE 功能。

Answer 2

进行这种数据绑定的技巧是使用两个数据源，一个包含讲座 ID、讲师姓名和主题 ID，另一个数据源仅包含主题列表。您可以使用任何 DataSource 控件来执行此操作 - 这是使用 SqlDataSource 的演示：

<!-- First data source is the main data source for the gridview -->
<asp:SqlDataSource runat="server" id="LectureDataSource" 
SelectCommand="SELECT l.LectureId, l.Lecturer, l.SubjectId, s.Subject FROM Lecture l INNER JOIN Subject s ON l.SubjectId = s.SubjectID" 
UpdateCommand="UPDATE Lecture SET Lecturer = @Lecturer, SubjectId = @SubjectId"
DeleteCommand="DELETE FROM Lecture WHERE LectureId = @LectureId" InsertCommand="INSERT INTO Lecture (Lecturer, SubjectId) VALUES (@Lecturer, @SubjectID)"
>
<DeleteParameters>
    <asp:ControlParameter ControlID="LectureGridView" Name="LectureId" 
        PropertyName="SelectedValue" />
</DeleteParameters>
<UpdateParameters>
    <asp:Parameter Name="Lecturer" />
    <asp:Parameter Name="SubjectId" />
</UpdateParameters>
</asp:SqlDataSource>

<!-- Second data source is the data source for the Subject dropdownlist -->
<asp:SqlDataSource runat="server" ID="SubjectDataSource"  
 SelectCommand="SELECT SubjectId, Subject FROM Subject ORDER BY SubjectId" />

<asp:GridView runat="server" AutoGenerateColumns="False" DataSourceID="LectureDataSource"
    ID="LectureGridView" DataKeyNames="LectureId" >
    <!-- Setting the DataKeyNames property allows us to delete by using the SelectedValue -->
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:LinkButton Text="Edit" runat="server" CommandName="Edit" /> 
                <asp:LinkButton Text="Delete" runat="server" CommandName="Delete" />
            </ItemTemplate>
            <EditItemTemplate>
                <asp:LinkButton Text="Update" runat="server" CommandName="Update" />
                <asp:LinkButton Text="Cancel" runat="server" CommandName="Cancel" />
            </EditItemTemplate>
            <ItemStyle HorizontalAlign="Center" />
        </asp:TemplateField>
        <asp:BoundField DataField="LectureId" HeaderText="Lecture Id" ReadOnly="true" />
        <asp:TemplateField HeaderText="Lecturer">
            <ItemTemplate>
                <asp:Label Text='<%# Bind("Lecturer") %>' runat="server" ID="LecturerLabel" />
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="LecturerEditTextBox" runat="server" Text='<%# Bind("Lecturer") %>'></asp:TextBox>
            </EditItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField>
            <ItemTemplate>
                <!-- The label is bound to the subject text field from the LectureDataSource -->
                <asp:Label ID="SubjectLabel" runat="server" Text='<%# Bind("Subject")  %>' />
            </ItemTemplate>
            <EditItemTemplate>
                <!-- In Edit mode the dropdownlist is bound to the SubjectDataSource, but we also set the text value from the LectureDataSource -->
                <asp:DropDownList ID="SubjectEditDropDownList" runat="server" DataSourceID="SubjectDataSource"
                    DataTextField="Subject" DataValueField="SubjectId" Text='<%# Bind("SubjectId") %>'>
                </asp:DropDownList>
            </EditItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>