使用下拉列表清空GridView，将数据表作为数据源

Question

我的表单显示空GridView以及添加新按钮。我在第1列中有一个下拉列表，它从数据库中填充。根据从下拉列表中选择的内容，我查询SQL数据库并填充第2列和第3列。我无法将下拉列表的值写入数据表并添加新行。当GridView只有文本框时，它运行良好，但添加数据绑定下拉列表使它很复杂。这是我的代码：

<asp:gridview ID="Gridview1" runat="server" ShowFooter="true" AutoGenerateColumns="false">
        <Columns>
        <asp:BoundField DataField="RowNumber" HeaderText="Row Number" />
        <asp:TemplateField HeaderText="Item Number">
            <ItemTemplate>
                <asp:DropDownList ID="ddlItemNumber" runat="server" DataSourceID="sdsSubjects" DataTextField="item_num" DataValueField="item_num" OnSelectedIndexChanged="Index_Changed" AutoPostBack="true" OnDataBound="addDefaultValue_DataBound">
                </asp:DropDownList>
                <asp:SqlDataSource ID="sdsSubjects" runat="server" connectionstring="<%$ ConnectionStrings:test%>"
                    SelectCommand="SELECT item_num FROM tblItemList"></asp:SqlDataSource>
                <asp:RequiredFieldValidator ID="reqItemNumber" ValidationGroup="ValgrpCust" ControlToValidate="ddlItemNumber" runat="server" ErrorMessage="Required"></asp:RequiredFieldValidator>                                    
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Description">
            <ItemTemplate>
                <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Unit">
            <ItemTemplate>
                <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Quantity">
            <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>

这是我的代码背后：

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

protected void addDefaultValue_DataBound(object sender, EventArgs e)
{
    DropDownList list = sender as DropDownList;

    if (list != null)
    {
        list.Items.Insert(0, "--Select One--");
    }
}

private void SetInitialRow()
{
    DataTable dt = new DataTable();
    DataRow dr = null;
    dt.Columns.Add(new DataColumn("Item Number", typeof(string)));
    dt.Columns.Add(new DataColumn("Description", typeof(string)));
    dt.Columns.Add(new DataColumn("Unit", typeof(string)));
    dt.Columns.Add(new DataColumn("Quantity", typeof(string)));
    dr = dt.NewRow();
    dr["Item Number"] = string.Empty;
    dr["Description"] = string.Empty;
    dr["Unit"] = string.Empty;
    dr["Quantity"] = string.Empty;
    dt.Rows.Add(dr);

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

    Gridview1.DataSource = dt;
    Gridview1.DataBind();
}
private void AddNewRowToGrid()
{
    int rowIndex = 0;

    if (ViewState["CurrentTable"] != null)
    {
        DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
        DataRow drCurrentRow = null;
        if (dtCurrentTable.Rows.Count > 0)
        {
            for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
            {
                //extract the TextBox values
                DropDownList ddlList1 = (DropDownList)Gridview1.Rows[rowIndex].FindControl("ddlItemNumber");
                TextBox box1 = (TextBox)Gridview1.Rows[rowIndex].FindControl("TextBox1");
                TextBox box2 = (TextBox)Gridview1.Rows[rowIndex].FindControl("TextBox2");
                TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].FindControl("TextBox3");

                drCurrentRow = dtCurrentTable.NewRow();
                //drCurrentRow["Ro wNumber"] = i + 1;
                dtCurrentTable.Rows[i - 1]["Item Number"] = ddlList1.SelectedItem.Text;
                dtCurrentTable.Rows[i - 1]["Description"] = box1.Text;
                dtCurrentTable.Rows[i - 1]["Unit"] = box2.Text;
                dtCurrentTable.Rows[i - 1]["Quantity"] = box3.Text;

                rowIndex++;
            }
            dtCurrentTable.Rows.Add(drCurrentRow);
            ViewState["CurrentTable"] = dtCurrentTable;

            Gridview1.DataSource = dtCurrentTable;
            Gridview1.DataBind();
        }
    }
    else
    {
        Response.Write("ViewState is null");
    }

    //Set Previous Data on Postbacks
    SetPreviousData();
}
private void SetPreviousData()
{
    int rowIndex = 0;
    if (ViewState["CurrentTable"] != null)
    {
        DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
        DataTable dt = (DataTable)ViewState["CurrentTable"];
        if (dt.Rows.Count > 0)
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                DropDownList ddlList1 = (DropDownList)Gridview1.Rows[rowIndex].FindControl("ddlItemNumber");
                TextBox box1 = (TextBox)Gridview1.Rows[rowIndex].FindControl("TextBox1");
                TextBox box2 = (TextBox)Gridview1.Rows[rowIndex].FindControl("TextBox2");
                TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].FindControl("TextBox3");

                ddlList1.SelectedItem.Text = dt.Rows[i]["Item Number"].ToString();
                box1.Text = dt.Rows[i]["Description"].ToString();
                box2.Text = dt.Rows[i]["Unit"].ToString();
                box3.Text = dt.Rows[i]["Quantity"].ToString();

                rowIndex++;
            }
        }
    }
}

protected void Index_Changed(Object sender, EventArgs e) {
    DropDownList ddlItemNumber = (DropDownList)sender;
    GridViewRow grdrDropDownRow = ((GridViewRow)ddlItemNumber.Parent.Parent);
    int index = grdrDropDownRow.RowIndex;        
    //lblMessage.Text = ddlItemNumber.SelectedItem.Text;
    DataSet myDataSet = GetData("SELECT description, unit FROM tblItemList WHERE item_num='" + ddlItemNumber.SelectedItem.Text.Trim
    () + "'");
    grdrDropDownRow.Cells[1].Text = myDataSet.Tables[0].Rows[0]["description"].ToString(); 
    grdrDropDownRow.Cells[2].Text = myDataSet.Tables[0].Rows[0]["unit"].ToString();
    DataTable dt = (DataTable)ViewState["CurrentTable"];
    if (dt.Rows.Count > 0)
    {
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            dt.Rows[i]["Item Number"] = grdrDropDownRow.Cells[1].Text;
            dt.Rows[i]["Description"] = grdrDropDownRow.Cells[2].Text;
            dt.Rows[i]["Unit"] = grdrDropDownRow.Cells[3].Text;
            dt.Rows[i]["Quantity"] = grdrDropDownRow.Cells[4].Text;
        }
    }
    SetPreviousData();
}

private DataSet GetData(string query)
{
    string conString = ConfigurationManager.ConnectionStrings["test"].ConnectionString;
    SqlCommand cmd = new SqlCommand(query);
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            using (DataSet ds = new DataSet())
            {
                sda.Fill(ds);
                return ds;
            }
        }
    }
}

感谢您提供任何线索和时间。

乔