单击按钮时Gridview总是添加新行？

Question

我正在编写单击按钮时在 gridview 中创建新行的代码。行数由文本框中的值创建。例如：当我在文本框中输入值 2 时，当然会添加两行，但是当我再次单击按钮时，仍然添加第三行。请在此处查看我的代码：

ASPX

<asp:TextBox ID="txtVisitor" runat="server"></asp:TextBox>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:GridView ID="Gridview1" runat="server" ShowFooter="true" AutoGenerateColumns="false">
            <Columns>
                <asp:BoundField DataField="RowNumber" HeaderText="Row Number" />
                <asp:TemplateField HeaderText="Header 1">
                    <ItemTemplate>
                        <asp:TextBox ID="txtDate" runat="server"></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Header 2">
                    <ItemTemplate>
                        <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Header 3">
                    <ItemTemplate>
                        <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
                    </ItemTemplate>
                    <FooterStyle HorizontalAlign="Right" />
                    <FooterTemplate>
                        <asp:Button ID="ButtonAdd" runat="server" Text="Add New Row" OnClick="ButtonAdd_Click" />
                    </FooterTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
    </ContentTemplate>
</asp:UpdatePanel>

Code_Behind

protected void ButtonAdd_Click(object sender, EventArgs e)
{
    int visitors = Convert.ToInt32(txtVisitor.Text);
    AddNewRowToGrid(visitors);
}

private void SetInitialRow()
{
    DataTable dt = new DataTable();
    DataRow dr = null;
    dt.Columns.Add(new DataColumn("RowNumber", typeof(string)));
    dt.Columns.Add(new DataColumn("Column1", typeof(string)));
    dt.Columns.Add(new DataColumn("Column2", typeof(string)));
    dt.Columns.Add(new DataColumn("Column3", typeof(string)));
    dr = dt.NewRow();
    dr["RowNumber"] = 1;
    dr["Column1"] = string.Empty;
    dr["Column2"] = string.Empty;
    dr["Column3"] = string.Empty;
    dt.Rows.Add(dr);
    //dr = dt.NewRow();

    //Store the DataTable in ViewState
    ViewState["CurrentTable"] = dt;

    Gridview1.DataSource = dt;
    Gridview1.DataBind();
}

private void AddNewRowToGrid(int visitors)
{
    if (ViewState["CurrentTable"] != null)
    {
        DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
        DataRow drCurrentRow;
        if (dtCurrentTable.Rows.Count > 0)
        {
            int rowindex = 0;

            for (int i = 1; i < visitors; i++)
            {
                //extract the TextBox values
                TextBox box1 = (TextBox)Gridview1.Rows[rowindex].Cells[1].FindControl("txtDate");
                TextBox box2 = (TextBox)Gridview1.Rows[rowindex].Cells[2].FindControl("TextBox2");
                TextBox box3 = (TextBox)Gridview1.Rows[rowindex].Cells[3].FindControl("TextBox3");

                drCurrentRow = dtCurrentTable.NewRow();
                drCurrentRow["RowNumber"] = i + 1;
                drCurrentRow["Column1"] = box1.Text;
                drCurrentRow["Column2"] = box2.Text;
                drCurrentRow["Column3"] = box3.Text;
                dtCurrentTable.Rows.Add(drCurrentRow);
                drCurrentRow = null;
                rowindex++;
            }
            //add new row to DataTable

            //Store the current data to ViewState
            ViewState["CurrentTable"] = dtCurrentTable;

            //Rebind the Grid with the current data
            Gridview1.DataSource = dtCurrentTable;
            Gridview1.DataBind();
        }
    }
    else
    {
        Response.Write("ViewState is null");
    }
}

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

Answer 1

这是您的代码的问题 #1：

for (int i = dtCurrentTable.Rows.Count; i < visitors; i++)
            {
                //extract the TextBox values
                TextBox box1 = (TextBox)Gridview1.Rows[rowindex].Cells[1].FindControl("txtDate");
                TextBox box2 = (TextBox)Gridview1.Rows[rowindex].Cells[2].FindControl("TextBox2");
                TextBox box3 = (TextBox)Gridview1.Rows[rowindex].Cells[3].FindControl("TextBox3");

                drCurrentRow = dtCurrentTable.NewRow();
                drCurrentRow["RowNumber"] = i + 1;
                drCurrentRow["Column1"] = box1.Text;
                drCurrentRow["Column2"] = box2.Text;
                drCurrentRow["Column3"] = box3.Text;
                dtCurrentTable.Rows.Add(drCurrentRow);
                drCurrentRow = null;
                rowindex++;
            }

你将 i 设置为 1 将其替换为gridview的行数 从它开始

Answer 2

这是您的代码的问题 #1：

//extract the TextBox values
TextBox box1 = (TextBox)Gridview1.Rows[rowindex].Cells[1].FindControl("txtDate");
TextBox box2 = (TextBox)Gridview1.Rows[rowindex].Cells[2].FindControl("TextBox2");
TextBox box3 = (TextBox)Gridview1.Rows[rowindex].Cells[3].FindControl("TextBox3");

这个逻辑是有缺陷的，甚至没有必要，因为当你绑定网格时，它会遍历你作为DataSource 提供的集合，并使用你在标记中定义的TemplateFields 来创建每一行。

在绑定到数据源（在您的情况下为 DataTable）之前，这些行实际上并未添加到 GridView，如下所示：

Gridview1.DataSource = dt;
Gridview1.DataBind();

第 1 步是从您的 AddNewRowToGrid 方法中删除 FindControl 行。

我什至不确定您要在代码中完成什么。