使用空数据源显示 Gridview 的页眉/页脚？答案

【问题标题】：Show header/footer of Gridview with empty data source?使用空数据源显示 Gridview 的页眉/页脚？
【发布时间】：2010-04-26 08:05:08
【问题描述】：

如何使用空数据源显示 Asp.Net Gridview 的页眉/页脚？

【问题讨论】：

标签： .net asp.net vb.net gridview

【解决方案1】：

阅读this article

或者，您可以使用EmptyDataTemplate property 为空数据行定义自己的自定义用户界面。

【讨论】：

实际上我更喜欢 EmptyDataTemplate 而不是 Bind Empty DataSet 到 GridView，我一直在这样做，它有很多问题，这就是为什么他们实际上放 EmptyDataTemplate。我指责微软没有实现这样的功能，但将空数据集绑定到 GridView 并不是最好的方法。

【解决方案2】：

您也可以通过为网格的 DataSource 分配一个虚拟行来做到这一点。默认情况下，数据源将填充虚拟行。所以网格也会显示页脚和虚拟行。要隐藏该行，您可以添加一个虚拟字段来确定是否显示控件。并将该字段绑定到控件的 Visible 属性。最后，当您将实际行添加到数据源时...删除您创建的虚拟行。

示例 - 来源：

    <asp:GridView ID="grdQualify" runat="server" Width="100%" AutoGenerateColumns="False" ShowFooter="true"
                        EnableModelValidation="True">
                        <Columns>
                            <asp:TemplateField HeaderText="Qualifying Exam">
                                <ItemTemplate>
                                    <asp:TextBox ID="txtQualifyingExam" runat="server" Text='<%# Eval("QualifyingExam") %>' Visible='<%# Eval("ShowVisible") %>'></asp:TextBox>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtQualifyingExamF" runat="server"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Roll Number">
                                <ItemTemplate>
                                    <asp:TextBox ID="txtRollNumber" runat="server" Text='<%# Eval("RollNumber") %>' Visible='<%# Eval("ShowVisible") %>'></asp:TextBox>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtRollNumberF" runat="server"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Admission Round">
                                <ItemTemplate>
                                    <asp:TextBox ID="txtAdmissionRound" runat="server" Text='<%# Eval("AdmissionRound") %>' Visible='<%# Eval("ShowVisible") %>'></asp:TextBox>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtAdmissionRoundF" runat="server"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Marks Obtained">
                                <ItemTemplate>
                                    <asp:TextBox ID="txtMarksObtained" runat="server" Text='<%# Eval("MarksObtained") %>' Visible='<%# Eval("ShowVisible") %>'></asp:TextBox>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtMarksObtainedF" runat="server"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Marks Out of">
                                <ItemTemplate>
                                    <asp:TextBox ID="txtMarksOutOf" runat="server" Text='<%# Eval("MarksOutOf") %>' Visible='<%# Eval("ShowVisible") %>'></asp:TextBox>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtMarksOutOfF" runat="server"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Percentage">
                                <ItemTemplate>
                                    <asp:TextBox ID="txtPercentage" runat="server" Text='<%# Eval("Percentage") %>' Visible='<%# Eval("ShowVisible") %>'></asp:TextBox>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtPercentageF" runat="server"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Remarks">
                                <ItemTemplate>
                                    <asp:TextBox ID="txtRemarks" runat="server" Text='<%# Eval("Remarks") %>' Visible='<%# Eval("ShowVisible") %>'></asp:TextBox>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtRemarksF" runat="server"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:Button ID="btnDeleteQualify" runat="server" Text="Delete" 
                                        Visible='<%# Eval("ShowVisible") %>' onclick="btnDeleteQualify_Click"></asp:Button>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:Button ID="btnAddQualify" runat="server" Text="Add" 
                                        onclick="btnAddQualify_Click"></asp:Button>
                                </FooterTemplate>
                            </asp:TemplateField>
                        </Columns>
                    </asp:GridView>

示例 - 代码：

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {

            if (ViewState["QualifyDetails"] == null)
                ViewState["QualifyDetails"] = new List<Entity_StudentAcademicQualify>();
            GridDataBindQualify((List<Entity_StudentAcademicQualify>)ViewState["QualifyDetails"]);
        }
    }


    private void GridDataBindQualify(List<Entity_StudentAcademicQualify> list)
    {
        if (list.Count == 0)
        {
            Entity_StudentAcademicQualify studentQualify = new Entity_StudentAcademicQualify();

            studentQualify.ShowVisible = false;
            studentQualify.QualifyingExam = string.Empty;
            studentQualify.RollNumber = string.Empty;
            studentQualify.AdmissionRound = string.Empty;
            studentQualify.MarksObtained = 0;
            studentQualify.MarksOutOf = 0;
            studentQualify.Percentage = 0;
            studentQualify.Remarks = string.Empty;

            list.Add(studentQualify);
        }
        else
        {
            list.RemoveAt(0);
        }

        grdQualify.DataSource = list;
        grdQualify.DataBind();

        ViewState["QualifyDetails"] = list;
    }

    protected void btnAddQualify_Click(object sender, EventArgs e)
    {
        GridViewRow row = (GridViewRow)((Button)sender).Parent.Parent;

        List<Entity_StudentAcademicQualify> studentQualifys =
            (List<Entity_StudentAcademicQualify>)ViewState["QualifyDetails"];

        Entity_StudentAcademicQualify studentQualify = new Entity_StudentAcademicQualify();

        studentQualify.ShowVisible = true;
        studentQualify.QualifyingExam = ((TextBox)row.FindControl("txtQualifyingExamF")).Text;
        studentQualify.RollNumber = ((TextBox)row.FindControl("txtRollNumberF")).Text;
        studentQualify.AdmissionRound = ((TextBox)row.FindControl("txtAdmissionRoundF")).Text;
        studentQualify.MarksObtained = Convert.ToInt32(((TextBox)row.FindControl("txtMarksObtainedF")).Text);
        studentQualify.MarksOutOf = Convert.ToInt32(((TextBox)row.FindControl("txtMarksOutOfF")).Text);
        studentQualify.Percentage = Convert.ToInt32(((TextBox)row.FindControl("txtPercentageF")).Text);
        studentQualify.Remarks = ((TextBox)row.FindControl("txtRemarksF")).Text;

        studentQualifys.Add(studentQualify);

        GridDataBindQualify(studentQualifys);
    }

    protected void btnDeleteQualify_Click(object sender, EventArgs e)
    {
        List<Entity_StudentAcademicQualify> studentQualifys =
          (List<Entity_StudentAcademicQualify>)ViewState["QualifyDetails"];

        studentQualifys.RemoveAt(((GridViewRow)((Button)sender).Parent.Parent).RowIndex);

        GridDataBindQualify(studentQualifys);
    }

【讨论】：

【解决方案3】：

我在网上阅读了很多关于此的帖子，最后我想出了自己的解决方案，可以满足我的需求，并希望能满足其他人的需求，包括这个问题。

需要显示页眉/页脚可能是因为 1）我希望用户看到网格的结构，并且 2) 我想使用页脚向表格中添加新数据。

因此，仅显示“没有可用数据”是不够的。

所以我的解决方案是测试数据是否可用。如果没有，则创建数据源的结构并使用默认值填充一行的必填字段。这很重要，因为如果在布尔值和日期等字段为空时将数据源绑定到网格，则会出现“DBNull”错误。然后将此新数据源绑定到网格。然后按此顺序隐藏该行。

Protected Sub BindGrid()
    con = New SqlConnection("mainLocal")
    Dim da As New SqlDataAdapter("SELECT * FROM Test", con)
    Dim dt As New DataTable()
    da.Fill(dt)

    dim rows as integer = dt.Rows.Count
    If rows = 0 Then
        Dim dr As DataRow = Nothing

        dr = dt.NewRow()
        dr("isActive") = False
        dr("Dated") = Date.Now()
        dt.Rows.Add(dr)
    End If

    Me.TestGridView.DataSource = dt
    Me.TestGridView.DataBind()
    If rows = 0 Then Me.TestGridView.Rows(0).Visible = False
End Sub

我想更简单、更短、更整洁！

【讨论】：